IACS Institutional Repository

Saikia, Nayanmoni

Tiru, Banty

Handique, Dudumoni

Boruah, P K

Boruah, K

Indian 7. Phys. 82 (5), 627-631 (2008) 
Programmable trigger circuit for UHE cosmic ray detection 
by mini-array method: simulation with VHDL 
Nayanmoni Saikia1*, Banty Tiru1, Dudumoni Handique^, 
PKBorua^andKBoruah1 
department of Physics, Gauhdti University ,Guwahdti-781 014,Assam India 
-Department of Instrumentation & USICGauhati University, Guwahati 781 014 Assam India 
*E mail nayan075("»yahoo co in 
Abstract A trigger circuit (TC) to be used in the Mini Array Laboratory, Dept of Physics Gauhati University 
is designed using VHDL The Laboratory has been detecting Ultra High Energy Cosmic Ray (UHECR) Extensive 
Air Shower ( EAS) for the last 16 years The working of the trigger circuit and its advantage over the already 
existing hardware is discussed in this paper 
Keywords Ultra high energy Cosmic rayr Extensive air shower, Trigger circuit, Trigger pulse 
PACS No. 29 40 Mc,29 
1. Introduction 
Studies of giant air showers produced by UHECR has gained importance due to the 
astrophysical aspects relating to GZK cutoff [1] and primary mass composition [2,3]. As 
the intensity of UHECR is very low, large ground based particle detector array is required 
for detection. For example, the AGASA detector array situated in Japan consisting of 
111 particle detectors and 27 muon detectors covers an area of 100 sqkm, the Yakurtsk 
Array in U.S.S.R covers an area of 20sqkm and the Pierre Auger Project in Chicago 
consisting of Hybrid Ground based detector covers an area of 3000 sqkm. AGASA group 
has reported 57 events of energy (E) >4 x 1019eV and 8 events with E > 1020eV 
[4].Yakurtsk reported an air shower event with maximum E of (1.1±0.4) x 1020eV [5]. 
Thus the possibility of detection of UHECR using Mini-array (small number of detectors 
with small carpet area) is totally removed. But Prof J Linsley proposed a novel method for 
detecting and analyzing UHECR measuring the thickness of shower front at large core 
Corresponding Author 
© 2008 IACS 
628 Nayanmoni Saikia et a! 
distances by using a roof top Mini array [6-8].Based on this proposed method, a Mini-
array has been set up in the Dept of Physics, Gauhati University, Assam to detect tne-
UHECR[9]. This paper starts with a short description of the experimental set up usee: 
its limitations and finally simulates a circuit to overcome these difficulties using V H D L 
2. The experimental setup of the mini array 
The Mini array (MA) consists of 8 compact Plastic Scintillation Counters ( size:50x50x^ 
cm3 ) with a total carpet area of 2m2 placed inside a hut on the roof top of the Physics 
Building, Gauhati University, Assam [10] as in Figure 1. 
oooo' 
oooo M ADC 
TC Jl 
DSO 
zzz 
GPIB H 
PC 
MINI ARRAY 
HUT 
Figure 1. Block diagram of Mini-array set-up. 
The pulses from the scintillation counters after passing through 8 discriminators with a 
lower discrimination level of 60mV(above the maximum noise level of the detector) is fori 
to the Digital Storage Oscilloscope (TEKTRONIX TDS 2022, 200 MHz, 2 GS/s) and 
recording is done in a PC via GPIB interface(GPIB-PCI Nl-488.2). The recording starts 
by triggering the DSO by an external trigger circuit (TC) which produces a trigger pulse 
whenever a genuine UHECR EAS event occurs in the atmosphere. If there is a minimum 
of two particle pulses within a 2.5 //s time window, then the pulses are considered as 
generated by a genuine UHECR EAS event. Thus the TC first observes the total numbers 
of particle pulses within this stipulated time and whenever the minimum condition is satisfied 
Figure 2. The trigger circuit. 
Programmable trigger circuit for UHE cosmic ray detection etc 629 
it produces a trigger pulse of 30ns width to trigger the DSO. The total number as well as 
the arrival time difference of particle pulses within the time window are calculated off-line 
from the stored data, which corresponds to a particular energy of Primary Cosmic Ray 
at a particular core distance. Thus changing the triggering criterion i.e choosing the minimum 
number of particle pulses within the time window enables us to select different energies 
(within UHE range) of Primary Cosmic ray particles at a particular core distance[11]. 
3. The trigger circuit 
The trigger circuit consisting of IC74121, IC7493, IC7474 JC7411 and IC7404 as shown in 
the Figure 2, is capable of producing trigger pulse for a minimum of 2,4 or 8 number of 
incoming pulses per stipulated time[12]. 
Two snap shots of the TC output using artificial pulses from a function generator is 
shown in Figure 3. It is therefore not possible to trigger the recording for a specific 
number of incoming pulses. Moreover the selection criterion for recording cannot be fixed 
for 3,5,6, 7 as the minimum number of incoming pulses offers a limitation to confining 
the recording process in terms of energy of Primary Cosmic Ray particle. 
25uS 
L*« * « »> * » i w \ . *, w • * i* * \+'+ .» w-i—If • " • - * — * - M J 
[Chi 2.00 V HE 2.00 V\ M LOOMS Ch2/ 1.96 V 
; Trigger out put tor minimum 2 pulses within 2 uS 
;H 
Figure 3(a). Trigger output for 2 particles 
Chi 2.00 V BJQ 2 00 V\ M 1 OOjJS Ch2 / I 96 V 
Trigger out put tor minimum 4 pulses within ? uS 
Figure 3(b). Trigger output for 4 particles 
4. The Simulated Circuit using VHDL (Very high speed Integrated Circuit Hardware 
Description Language) 
We model the new trigger circuit using VHDL ( ModelSim SE 5.7g, evaluation version)[13] 
in the Top Level Behavioral Model.The block diagram of the model IC is shown in Figure 
din 4/ 
elk 
en 
1st-
IC-TE-07 
->tf 
->ts 
->tt 
• t f t 
t > countl 
> countl? 
count3 — ^ unu
—> count4 
Figure 4. Block diagram of the simulated circuit 
630 Nayanmoni Saikia et al 
4. The clock frequency in this simulation is 10 MHz which is very high compared to the 
frequency of secondary UHE cosmic ray particle in the ground level. 
The simulation is done only for 4 outputs corresponding to 4 input conditions. The 4 
inputs is fixed at 2, 3, 4, 5 particle pulses within the 2.5 ^ is time window. Thus output 1 
corresponds to the condition when there are only 2 particle pulses in the input, output 2 
corresponds to 3 incoming pulses and so on. Thus by observing or selecting the output 
we can restrict our recording as desired. Moreover each output is connected with an up 
counter which counts the number of output pulses. One snapshot of the simulation is 
shown in Figure 5. 
Figure 5. Snapshot of the simulated result. 
5. Results and conclusion 
A comparison of the existing and simulated TC (Table 1) shows that the latter has better 
triggering capabilities due to the fast rise and fall of the trigger pulse and offers a wide 
Table 1. Comparison between the Existing and Simulated Trigger Circuit 
Characteristics 
Rise Time 
Fall Time 
Pulse Width 
Selection Mode 
Trigger Pulse 
Counter 
No.of output 
Existing 
Trigger circuit 
10nS 
14ns 
32ns 
2,4,8(mm) 
no 
no 
Simulated 
Trigger Circuit 
8nS 
5ns 
100ns 
2,3,4,5 
Up Counter 
Depending on 
On Selection 
Mode 
Programmable trigger circuit for UHE cosmic ray detection etc 631 
range of selection criterions. Though here the pulse width is greater, there is no delay 
caused by the individual circuit elements. In our future work, we hope to implement this 
simulated circuit in FPGA (Field programmable gate array) or CPLD (Complex 
programmable logic device) and use it in the MA laboratory for precise studies on Cosmic 
Ray 
References 
[1] K Greisen Rhys. Rev. Lett 16 748(1996) 
[2] D J Bird, S C Carbato, H Y Dai, B R Dawson, J W Elbert, T K Gaisser, M H Huang, D B Kieda, S 
Ko, C G Larsen, E C Loh, M H Salamon, J D Smith, P Sokolsky, P Sommers, T Stanev, V S Tila. J 
K K Tang and S B Thomas 23^ Int Cosmic Ray Conf (Calgary, Alberta) 2 38 (1993) 
[3] N Hayashida, K Honda, M Honda, S Imaizumi, N Inoue, K Kadota, F Kakimoto, K Kamata and S 
Kawaguchi J Phys G 21 1101(1995) 
[4] AGASA collaboration Astro Particle Phys 19 447 (2003) 
[5] M N Dyakonov 22nd Int Cosmic Ray Conf 2 93 (1991) 
[6] J Linseley Research report, UNML (1993) 
[7] J Linseley J Phys. G. 12 51(1986) 
[8] J Linseley Phys Rev Lett, 9 51(1962) 
[9] T Bezboruah, K Boruah and P K Boruah Symposium on advances in Nuclear and Allied 
Instrumentation, BARC, Mumbai 1 498 (1997) 
[10] T Bezboruah, K Boruah and P K Boruah Nuclear Instruments and Methods in Physics Research 
A410. 2 206(1998) 
[11] T Hara, T Teshima, Y Matsubara, N Hayashida and M Honda 1&h Int Cosmic Ray Conf 1 276 
(1983) 
[12] N M Saikia, J P Phukan, S Rajbongshi, K Boruah and P K Boruah 29"' Int Cosmic Ray Conf 8 81 
(2005) 
[13] www.mentor.com 


English

Programmable Trigger Circuit for the Cosmic Ray Detection by Miniarray Method : Simulation with VHDL

Advisory Board and Editors

Sarkar, Nirmal Kumar

Choudhury, Joydeep

Bhattacharjee, Ramendu

Indian J Phys 82 (6), 767-772 (2008) 
Algebraic approach : study of vibrational spectra of some 
linear triatomic molecules 
Nirmal Kumar Sarkar1*, Joydeep Choudhuryr' and Ramendu Bhattacharjee 
department of Physics Kanmganj College Kanrnganj 788 710 Assam lndw» 
department of Physics Assam University Silcfuir 788 011 Assam India 
E mail nks sdstfi rediffmail com 
Abstract Using the Lie algebraic method the vibrational energy levels of OCS and HCN are calculated for 
35 vibrational bands each using the local Hamiltonian A comparative study is made between the two It has been 
shown that local Hamiltonian gives a much better fit to the HCN in comparison to that ot OCS Better result for HCN 
compared to those published earlier also has been reported 
Keywords Vibrational spectra Lie algebra OCS, HCN 
PACS Nos. 33 20Tp, 31 15 p 
1. Introduction 
Manus Sophus Lie introduced Lie algebras at the end of the 19th century However, Lie 
algebraic methods have been useful in the study of problems in Physics after the 
development of quantum mechanics in the first part of the 20th century The use of Lie 
algebras as a tool to systematically investigate physical systems (the so called spectrum 
generating algebras) did not however develop fully until the 1970's, when it was introduced 
in a systematic fashion by A Anma and F lachello in the study of spectra of atomic 
nuclei (interacting boson model) [1,2] Wulfman played a great role in the introduction of 
the algebraic approach to molecules[3] He is the pioneer to publish the first paper on the 
algebraic approach to molecules (the algebraic approach to the Morse oscillator) in 1979[3] 
Later, in 1981, F. lachello used Lie algebraic methods in the systematic study of spectra 
of molecules (vibron model) [4] After 1981, there was a rapid progress in the field The 
situation up to 1995 was reviewed in the study of F lachello and R.D Levine[5] The 
study of F.lachello and S Oss[6] presented a brief review of the work done in this field up 
Corresponding Author 
© 2008 IACS 
768 Nirmal Kumar Sarkar, Joydeep Choudhury and Ramendu Bhattacharjee 
to 2000 Moreover, the study[6] also provided perspectives for the algebraic method in the 
first decade of the 21st century 
In the Lie algebraic method there is provision to study a molecule both by a normal 
and a local Hamiltonian Using Lie algebraic method, in this paper the vibrational energy 
levels of OCS and HCN (in cm1) are calculated by local Hamiltonian for 35 vibrational 
bands each On the basis of this study it has been shown that local Hamiltonian gives a 
much better fit to the HCN in comparison to that of OCS Better result for HCN compared 
to those published earlier also has been reported. 
2. Theory : the Lie algebraic method [7] 
In Lie algebraic method to study the vibrational spectra of triatomic molecules, there are 
two main ways in which the bonds can be coupled [8] 
£/|(4)®f/2(4) D 0,(4)00,(4) D 012(4) D 0 |2(3) D 0 | 2(2) (I) (1) 
Ux(4)® U2(4) z> Ul2 (4) D 0I2(4) D 012O) D 0 | 2(2) (II) 
Which correspond to local and normal coupling respectively For these two situations the 
Hamiltonian operator can be diagonalized analytically 
The local basis is characterized by the representations of chain I [ 5, 8 ], 
17,(4) ® t/2(4) =) 0,(4) ® 02(4) 3 0p (4) D 0 l 2O) D 0 l2(2) i 
I i I i I i I ^ I (2) 
[N,] [N2J (cov0) (fi^.O) (TlfT2) J Mj i 
The numbers Nv N2 are the vibron numbers of each bond They are related to the 
number of bound states for bonds 1 and 2 respectively For Morse rovibrators they are 
given by the following equation [5] 
E'o = - A(2N + 3) (3) 
(E'oA —> algebraic parameters) 
Equation (3) shows that the vibron numbers are related to the depth of the 
potentials.They are fixed numbers for a given molecules. The numbers O),,Q)2,TVT2 are 
related to the vibrational quantum numbers, as discussed explicitly in the following sections 
We have written the 0,(4) representations as (^,0) and not simply as co1} since for 
coupled systems one can have representations of 0,(4) in which the second quantum 
number is not zero[5]. The values of co, and co2 are given by the rule 
(o, = Nv A/, - 2, 1 or 0, A/, = odd or even. 
o)2 s A/2, N2 - 2, 1 or 0, N2 = odd or even (4) 
Algebraic approach: Study of vibrational spectra of some linear tnatomic molecules 769 
The values of (r,, T2) are instead obtained from the direct product of representations 
[5]. They are given by [9] 
^ = °.
1
» — ,min (a^cog),!' - 0,1, ji (5) 
Finally for each representation (r^ r2) the values of the allowed angular momenta and 
parities are 
J> = 0M~, 2+, (r/ or r f ) , when t2 = 0 and (r, = even or odd) 
J " - T | , (T 2 + 1)", T ; When r2 / 0 (6) 
The z components of the angular momentum is given by the usual rule 
-J<Mj<+J. (7) 
3. Local-mode Hamiltonian for linear triatomic molecules 
Whenever the Hamiltonian can be written in terms of invanant(Casimir) operators of a 
chain, its eigen value problem can be solved analytically. This method can be applied to 
the construction of both local and normal Hamiltonians. For local Hamiltonians, one writes 
H in terms of Casimir invariants of equation (2) 
^locais Eo + AAC(0(4y)) + A2C(0(A2)) + 412C(0(412)) + eC(0(312)) (8) 
Here we have dropped the subscript 2 from the Casimir invariant operators in order to 
simplify the notation [5]. The Hamiltonian (8) is diagonal in the local basis with eigen 
values 
E(NvN2io)vo)2, rv T2, J, Mj) = Eo + >Vi K + 2) + V>2 K + 2 ) 
+ 4 2 [ M r i + 2 ) + T22] + W + 1)- (9) 
The last term in the right hand side of the above equation representing the rotational 
part. We can now convert equation (9) into the usual form by introducing the local 
vibrational quantum numbers[5], 
a), = N,-2va 
co2 = N2-2vc 
Tl =A/1+A/2-2va~v, )-2vc 
To =1h (10) 
770 Nirmal Kumar Sarkar, Joydeep Choudhury and Ramendu Bhattacharjee 
The quantum number va,vc denote local stretching vibrations, while the quantum 
numbers, vh,b .denote the doubly degenerate bending vibrations. Eq. (9) can be converted, 
using eq. (10) to 
*(v . .v / \v c ) = E & - ^ 
~^2[2{N,+N2+^{2va + vb + 2vc)-(2va + vb + 2vcf+^ (11) 
In this expression we have dropped the rotational part and written only the vibrational 
part. In this (purely local) limit, vibrational energy levels are determined by five 
parameters^.^.^2 and NVN2). 
4. Results and discussion 
Vibrational energy levels of OCS and those calculated in the strict local limit for 35 
vibrational bands are shown in Table 1. Vibrational energy levels of HCNand those calculated 
in the strict local limit for 35 vibrational bands are shown in Table 2. Using the established 
norms[5, 8] the vibron numbers NVN2 and other algebraic parameters AVA2,AA2 were 
determined. Av A2, A,2 all in cm'1, except N, and N2, which are dimensionless. 
Table 1 shows that in the calculation of vibrational energy levels, local Hamiltonian 
gives a poor fit to the OCS. Table 2 shows that local Hamiltonian gives a much better fit 
to the HCN in comparison to that of OCS [10]. Result reported here for HCN[7] is better 
with respect to the results published earlier [5, 8, 14]. RMS deviations(A(r.m.s.)) here we 
reported for OCS and HCN were 90.816 cnr1and 11.057 crrv1 respectively. 
5. Conclusion 
(i) On the basis of the cited data it may be concluded that result reported in this 
study is better with respect to the results published earlier for the vibrational 
spectra of HCN(using local model). 
(ii) In the comparative study of the vibrational spectra of OCS and HCN in the local 
mode limit we conclude : Local model is a poor approximation for OCS compared 
to that of HCN. Only HCN could be very well approximated by a local Hamiltonian 
but not OCS. 
6. Algebraic approach in the study of molecular spectra in near future 
Using the Lie algebraic methods many molecules(small and medium) have been analyzed 
in the last twenty five years. At present challenges for the Lie algebraic methods are the 
larger and more complex molecules (macromolecules, polymers, biomolecules and 
biopolymers). Introduction of anharmonicities gives the Lie algebraic methods an 
advantageous position. Some physical systems are known where anharmonicities play a 
role.Liquids and surfaces are the two important sectors belongs to this category[6]. It is 
Algebraic approach: Study of vibrational spectra of some linear tnatomic molecules 771 
Table 1. Vibron Model Fits of OCS (in c m ^ i o ] 
V'1 
1 
0 
0 
2 
1 
0 
1 
0 
0 
3 
2 
1 
0 
2 
1 
0 
1 
0 
0 
4 
3 
2 
3 
1 
0 
2 
1 
0 
1 
5 
4 
4 
2 
3 
2 
v? 
0° 
2° 
0° 
0° 
2° 
4° 
0° 
2° 
0° 
0° 
2° 
4° 
6° 
0° 
2° 
4° 
0° 
2° 
0° 
0° 
2° 
4° 
0° 
4° 
6° 
0° 
2° 
4° 
0° 
0° 
2° 
0° 
4° 
0° 
2° 
^3 
0 
0 
1 
0 
0 
0 
1 
1 
2 
0 
0 
0 
0 
1 
1 
1 
2 
2 
3 
0 
0 
0 
1 
1 
1 
2 
2 
2 
3 
0 
0 
1 
1 
2 
2 
Expt.8 
859 
1047 
2062 2 
1711 1 
1892 2 
2104 8 
2918 1 
3095 6 
4101 4 
2556 
2731 4 
2937 2 
3170 6 
3768 5 
3937 4 
4141 2 
4953 9 
5121 
61176 
3394 
3564 5 
3762 8 
4609 9 
4970 4 
5196 
5801 9 
5959 3 
6154 7 
6966 2 
4224 9 
4391 4 
5445 
5792 
6640 1 
6791 6 
Calc.b 
867 24 
1102 84 
2075 92 
1730 64 
1963 76 
2199 36 
2936 84 
3172 44 
4133 28 
2590 2 
2820 84 
3053 96 
3289 56 
3793 92 
4027 04 
4262 64 
4987 88 
5223 48 
6172 08 
3445 92 
3674 08 
3904 72 
4647 16 
5110 92 
5346 52 
5838 64 
6071 76 
6307 36 
7020 36 
4297 8 
4523 48 
5496 56 
5955 3 
6685 56 
6916 2 
Ac 
-8 24 
55 84 
-13 72 
-19 54 
-71 56 
-94 56 
-18 74 
76 84 
-31 88 
-34 2 
-89 44 
-116 76 
-118 96 
-25 42 
-89 64 
-121 44 
-33 98 
102 48 
-54 48 
51 92 
-109 58 
-141 92 
-37 26 
-140 52 
-150 52 
-36 74 
-112 46 
-152 66 
-54 16 
-72 9 
-132 08 
-51 56 
-163 36 
-45 46 
-124 6 
4(rm.s.) = 90 816 
aRef. [11] 
^ = 1 9 0 , A/2=159t ^ = 0 31, >l2=-1 53, /412=-0 79 
c 4 = ( Expt-Cal) 
Table 2. Vibron Model Fits of HCN (in cm })[7] 
v
'1 
1 
1 
0 
0 
1 
2 
0 
1 
0 
2 
1 
1 
0 
1 
1 
0 
0 
3 
2 
1 
0 
5 
0 
0 
1 
0 
1 
2 
0 
1 
0 
0 
0 
1 
0 
I 1' 
*2 
2° 
0° 
0° 
4° 
2° 
0° 
2° 
0° 
0° 
2° 
2° 
0° 
0° 
2° 
0° 
0° 
0° 
0° 
0° 
0° 
0° 
0° 
11 
31 
11 
11 
31 
11 
31 
11 
11 
2* 
4* 
22 
2* 
*3 
0 
0 
1 
0 
0 
0 
1 
1 
2 
0 
1 
2 
3 
2 
3 
4 
5 
3 
4 
5 
6 
2 
0 
0 
0 
1 
0 
0 
1 
1 
2 
0 
0 
0 
1 
Expt* 
1411 43 
2096 85 
3311 48 
2802 85 
3501 13 
4173 07 
4684 32 
5393 70 
6519 61 
5571 89 
6761 33 
8585 57 
9627 02 
9914 41 
11674 46 
12635 90 
15551 94 
15710 53 
16674 21 
17550 39 
18377 01 
16640 31 
711 98 
2113 46 
2805 58 
4004 17 
4201 29 
4878 27 
5366 86 
6083 35 
7194 75 
1426 53 
2818 16 
3516 88 
4699 21 
Calcb 
1412 972 
2104 012 
3299 364 
2810 832 
3501 872 
4183 040 
4697 224 
5388 264 
6503 344 
5565 788 
6771 012 
8577 132 
9611 94 
9944 768 
11670 616 
12625 152 
15542 98 
15713 016 
16687 296 
17571 432 
18365 424 
16622 444 
710 264 
2115 68 
2806 72 
4002 072 
4197 024 
4878 192 
5392 376 
6083 416 
7198 496 
1420 528 
2818 388 
3509 428 
4704 78 
X 
1 542 
7 162 
+12 116 
7 982 
-0 742 
9 97 
12 904 
+5 436 
+16 266 
+6 102 
-9 682 
+8 438 
+ 15 08 
30 358 
+3 844 
+10 748 
+8 96 
-2 486 
13 086 
-21 042 
+11 586 
+ 17 866 
+1 716 
-2 22 
-1 14 
+2 098 
+ 4 266 
+0 078 
-25 516 
-0 066 
-3 746 
+6 002 
-0 288 
+7 452 
-5 57 
d
 References [12] and [13] 
eA/1=140, A/2=47, V - 1 234« V * 1 0 0 3 4 ' Air5"1 8 8 9 ' 
1
 j = ( Expt - Cal) 
772 Nirmal Kumar Sarkar, Joydeep Choudhury and Ramendu Bhattacharjee 
another challenge for the Lie algebraic methods to expand its kingdom in to these regions 
in near future. 
In view of the many possible applications it is hoped that present momentum of the 
Lie algebraic method will stimulate further research, especially in the spectroscopy of 
higher-energy states of molecules[5] and new areas of complex systems for which alternative 
methods of analysis are difficult to apply. In this regard we are optimistic to hope that in 
near future the Lie algebraic methods will be able to open many new windows in the field 
of spectroscopy. 
Acknowledgment 
Nirmal Kumar Sarkar would like to thank Prof. S. Oss, Prof. R . Lemus and Prof. N. 
Manini for providing necessary co-operation for this study. Ramendu Bhattacharjee would 
like to thank The DST, Govt, of India for supporting the work. 
References 
[1 
[2] 
[3; 
[< 
[5; 
[e: 
[7; 
[8; 
[9: 
[io; 
[n 
[12: 
[13] 
IK 
F lachello and A Arima Phys Lett B53 309 (1974), A Arima and F lachello Phys Rev Lett 35 
1069 (1975) 
For a review see, F lachello and A Arima The Interacting Boson Model (Cambridge Cambridge 
University Press) (1987) 
C E Wulfman Chem Phys Lett 23 370 (1973), R D Levine and C E Wulfman Chem Phys Lett 60 
372 (1979) 
F lachello Chem Phys Lett 78 581 (1981) 
F lachello and R D Levine Algebraic Theory of Molecules (Oxford Oxford University Press) 
(1995) 
F lachello and S Oss Eur Phys J D 19 307 (2002) 
Nirmal Kumar Sarkar, Joydeep Choudhury and Ramendu Bhattacharjee Mol Phys 104 3051 (2006) 
S Oss Algebraic Models in Molecular Spectroscopy, Dipartimento di Fisica- Universita di Trento 
and Istituto Nazionale di Fisica della Materia, Unita di Trento, Povo (TN), Italy, (1996) 
R Lemus Casillas PhD thesis, Universidad Nacional Autonoma de Mexico, (1988) 
Nirmal Kumar Sarkar, Joydeep Choudhury and Ramendu Bhattacharjee Proceedings of the First 
Asian Spectroscopy Conference and Asian Biospectroscopy Conference, 106 (2007) 
E E Aubanel and D M Wardlaw J Chem Phys 88 495 (1987), A Fayt Ann Soc So Brux 86 61 
(1972) 
T Nakhagawa and Y Monno Bull Chem Soc. Jpn 42 2212 (1969) 
S N Suchard Spectroscopic Data, Part A (New York Plenum) (1975) 
O van Roosmalen, F lachello, R D Levine and A E L Diepermk J Chem Phys. 79 2515 (1983) 


Algebraic Approach : Study of Vibrational Spectra of some Linear Triatomic Molecules

Phukan, Manisha

Sarma, B K

Indian / Phvs 82 (6), 773-777 (2008) 
X-ray and infrared spectroscopic studies of the molecular 
structure of 3-(2,4-dichlorophenyl)-l-phenylprop-
2-en-l-one 
Manisha Phukan and B K Sarma* 
Department of Physics Gauhati University, Guwahati -781 014 Assam India 
h-mail bannksl6(c/yahoo Lorn 
Abstract The title compound C15H10CI2O is derived from acetophenone and 2,4-dichlorobenzaldehyde 
There are two molecules in the asymmetric unit of the molecular structure of the compound The two aromatic 
rings exhibit a non-coplanar geometry, which is due to the presence of two chlorine atoms in one aromatic ring 
The compound was further characterized by infrared spectroscopy where a band at 1661 cm 1 indicates the 
presence of the carbonyl group 
Keywords Chalcone, Infrared spectroscopy, X-ray diffraction, single crystal 
PACS Nos. 87 64 Bx, 87 64 km 
1. Introduction 
Chalcones are the important group of natural products [1] which have wide pharmacological 
properties. Some chalcones possess anticancer [2], antimalarial [3], antimicrobial [4], 
and anti-inflammatory [5] activities. A new chalcone derivative, namely 3-(2,4-dichlorophenyl)-
1-phenylprop-2-en-1-one, has been synthesized by condensation of acetophenone and 2,4-
dichlorobenzaldehyde in alkaline medium. The molecular structure of the synthesized 
chalcone was determined by analyzing the single crystal X-ray diffraction data [6]. Further 
characterization of the compound was done by using infrared spectroscopy. 
2. Experimental details 
2.1. Synthesis of3-(2A-dichlorophenyl)-1-phenylprop-2-en-1-one: 
2,4-Dichlorobenzaldehyde (8.74 g, 0.05 mol), acetophenone (6 g, 0.05 mol) and sodium 
hydroxide (0.1 g, 0.0025 mol) were dissolved in 50 mL methanol. The reaction mixture 
* Corresponding Author 
©2008IACS 
774 Manisha Phukan and B K Sarma 
was stirred at 298 K for 24 hours. The solution is cooled and the solid precipitated out 
was collected. A second crop was obtained by evaporating a part of the solvent. Finally, 
the product was recrystallized from methanol to give colourless needle like crystals (yield: 
59%, mp. 345-346 K). 
2.2. X-ray Measurements: 
The X-ray diffraction measurements were carried out in Bruker SMART CCD diffractometer 
at room temperature. The crystal structure was solved and refined by using SHELX97 [7]. 
The crystal data and details of the X-ray analysis are given in Table 1. 
Table 1. Crystal data and structure refinement. 
Molecular Formula 
Formula weight 
Temperature 
Crystal system 
space group 
Unit cell dimensions 
a 
b 
c 
a 
P 
Y 
Volume 
Z 
C15H10CI2O 
277.13 
293 (2) K 
Triclinic 
P T 
3.9712 (1) A° 
11.7738 (4) A° 
27.7962 (10) A° 
90.748 (2)° 
91.268 (2)° 
96.492 (2)° 
1290.83 (7)A°3 
4 
Radiation 
Calculated Density 
Adsorption coefficient 
F(000) 
Crystal size 
Reflections collected /unique 
S Range for data collection 
Completeness to o = 
Refinement method: 
Data/parameters 
Goodness-of-fit on F2 
Final R indices 
R indices (all data) 
Largest diff. peak and 
28.4 
hole 
Mo Ka 
1.426 Mgm' 3 
0 49 mm1 
568 0 
0.42 x 0.15 x 0.12 mm 
16672/5889 
0.7 - 28.4° 
90 % 
Full-matrix least-squares on F2 
5889/325 
1.040 
R1 0.064, wR2 0.162 
R1 0.118, wR2 0.189 
0.416 and -0.245 eA*'3 
2.3. Infrared Spectroscopic measurements: 
The IR spectra of 3-(2,4-dichlorophenyl)-1-phenylprop-2-en-1-one was recorded in KBr matrix 
at 300 QK using a Perkin Elmer RX1 FT-IR spectrophotometer. 
3. Results and discussions 
3.1. X-Ray Crystallography: 
The structure of 3-(2,4-dichlorophenyl)-1-phenylprop-2-en-1-one with atomic labelling is given 
in Figure 1. The crystals are triclinic, space group P ?, with four formula units per unit-
cell. The molecular structure of the compound contains two molecules in the asymmetric 
unit (Figure 1). Two benzene rings derived from acetophenone and 2,4-dichlorobenzaldehyde 
exhibit a non-coplanar geometry, making dihedral angles of 38.74 (9)° and 33.22 (11)° in 
the two molecules. This is in contrast to a previously reported derivative of chalcone, 2'-
X-ray and infrared spectroscopic studies of the molecular structure etc 775 
hydroxy-4"-dimethylaminochalcone, in which a dihedral angle of 10.32° is observed between 
the rings [8]. The non-coplanarity of the two rings is due to the presence of two chlorine 
atoms on one ring. The mean C—C bond length of 1.3739 (5) A in the rings of the 
molecule of the title compound shown in Figure 1 compares well with other reported 
derivatives of chalcone (1.34 A : Liu et al [8]; 1.39 A : Murafuji et al [9]). 
Figure 1. Two asymmetric units of the compound in the crystal lattice 
The double-bond character of the bond between C7 and C8 is deduced from the short 
bond distance [1.314 (5) A]. [The value in the other molecule is 1.319 (4) A for C22— 
C23]. The average C—CI and C—O bond lengths of 1.7375 (4) and 1.2185 (4) A, 
respectively, for the first molecule (Figure 1) are also well within the expected range. The 
orientation of the rings with respect to the double bond may be described by the torsion 
angles C5—C4—C7—C8 = 10.5 (7)° and C8—C9—C10—C15 = 18.5 (6)°. The torsion 
angles for the second molecule are C20—C19—C22—C23 = 24.8 (5) and C23—C24— 
C25—C30 = -1.6 (5) A. 
Figure 2. Unit Packing diagram (A) and supramolecular assembly (B) of the compound 
776 Manisha Phukan and B K Sarma 
A supramolecular assembly of 3-(2,4-dichlorophenyl)-1-phenylprop-2-en-1-one (Figure 2) 
is formed due to C-H-0 interaction of the oxygen atom of a chalcone with one hydrogen 
atom of another molecule. The second factor which is influencing the supramolecular 
architecture is the n-n interactions of the phenyl rings in the molecule. The compound 
exists in an assembly of sheets due to these C-H....0 and n-n interactions. 
cm" 
Figure 3. IR spectrum of the compound 
3.2. Infrared Spectroscopy: 
IR spectrum of the compound (Figure 3) is in excellent agreement with the results of the 
crystal structure analysis. In this spectrum two prominent bands around 1661 cm*1 are 
due to the presence of the C = 0 group. A broad band at 1603 cm"1 (in the form of a 
doublet) is due to phenyl rings as well as the olefinic bond. Bands in the range 2724-
3058 cm*1 are due to C-H stretching vibrations whereas C-H bending vibrations appear at 
1384 cm*1 and 1466 cm'1. Strong bands in the range 712-978 cm1 is due to C-H bending 
vibrations of the phenyl ring. A prominent peak at 680 cm*1 is due the presence of C-CI 
bond. 
Acknowledgment 
Financial support from UGC(NERO), (Grant No. F.5-36/2005-06/MRP/ NERO/1554) is 
gratefully acknowledged. We are also thankful to the Head, Chemistry Deptt. Gauhati 
University for laboratory and analytical facilities and IIT Guwahati for Single Crystal X-ray 
data. 
X-ray and infrared spectroscopic studies of the molecular structure etc 111 
References 
[1] D M Tomazela, M T Pupo, E A P Passador, M F G F da Silva, P C Vieira, J B Fernandas. F E 
Rodngues, G Oliva and J R Pirani Phytochemistry 55 643 (2000) 
[2] (a) L W Wattenberg, J B Coccia and A R Galbraith Cancer Lett 83 165 (1994) (b) A T Dmkova, 
Kostova, C Abeygunawardana and P Talalay J Med Chem 41 5287 (1998) 
[3] V J Ram, A S Saxena, S Snvastava and S Chandra Bioorg Med Chem Lett 10 2159 (2000) 
[4] M Kidwai, P Sapra, P Misra, R K Saxena and M Singh Bioorg Med Chem 9 217 (2001) 
[5] J F Ballesteros, M J Sanz, A Ubeda, M A Miranda, S Iborra. M Paya and M J Alcaraz J Med 
Chem 38 2794 (1995) 
[6] M Phukan, P Phukan, R Chakrabarty and B K Sarma Acta Cryst E62 05056 (2006) 
[7] (a) G M Sheldrick Acta Cryst A46 467 (1990) (b) G M Sheldrick SHELXS97 and SHELXL97 
(Germany University of Gottmgen) (1997) 
[8] 7 -Q Liu, Q Fang, W -T Yu, G Xue, D -X Cao and M -H Jiang Acta Cryst C58 o445 (2002) 
[9] T Murafuji, Y Sugihara, T Monya, Y Mikata and S Yano New J Chem 23 683 (1999) 


X-Ray and Infrared Spectroscopic Studies of the Molecular Structure of 3-(2,4-Dichlorophenyl)-1-Phenylprop-2-En-1-One

Raghusankar, M

Sarma, Sidananda

Ravi, S

Srinivasan, A

hulicmJ Phys 82(2), 169-172(2008) 
% 
Magnetic and martensitic transformations in 
Ni-Fe-Ga alloy 
M Raghusankar, Sidananda Sarma, S Ravi and A Srinivasan" 
Department of Physics Indian Institute of Technology Guwahati 
Guwahati 781 039 Assam India 
E-mail asnnXaiutg ernet in 
Abstract Magnetic and martensitic transformations have been observed in Ni4BFe^Ga^ alloy prepared by 
arc melting AC magnetic susceptibility technique was employed to determine the martensitic transformation and 
Curie temperature Room temperature optical and scanning electron microscopy investigations were performed 
to ascertain the presence of the martensite phase and to determine the overall alloy composition The alloy 
exhibited a ferromagnetic martensitic phase below 237 K 
Keywords Ferromagnetic shape memory alloy, ac susceptibility Curie temperature martensitic transformation 
PACS Nos. 75 90 +w 75 50 Cc, 81 30 Kf 
1. Introduction 
Ferromagnetic shape memory alloys (FSMAs), which exhibit both shape memory effect 
as well as ferromagnetism, are potential candidates for next generation actuator 
applications Ullakko [1] reported a large magnetic field induced strain of ~ 6% in a 
Ni2MnGa single crystal Practical application of the prototype FSMA, Ni2MnGa is restricted 
due to its extreme bnttleness in the polycrystallme state and requirement of high magnetic 
field for inducing the required strain Recently, the Ni-Fe-Ga alloy, which is similar to Ni-
Mn-Ga alloy in structure, was shown to undergo reversible thermo elastic martensitic 
transformation in ferromagnetic state [2-7] The preliminary results of work done on 
Ni48Fe20Ga32 alloy are reported here 
2. Experimental details 
Ni48Fe20Ga32 alloy was prepared by arc melting appropriate amounts of the constituent 
elements in an argon atmosphere. All the investigations were carried out on ascast sample 
The overall composition and microstructure of the alloy were determined using a scanning 
Corresponding Author 
©2008 I ACS 
170 M Raghusankar, Sidananda Sarma, S Ravi and A Srinivasan 
electron microscope (LEO1430 VP) equipped with an energy dispersive spectrometer (EDS, 
AZTEC) and an optical microscope (Zeiss Axiotech). An X-ray diffractometer (Seifert 3003TT) 
equipped with an X-ray tube with Cu target (wavelength = 1.5406 A) was used for crystal 
structure elucidation. AC susceptibility (ACS) measurements were carried out using an 
indigenously developed [8] mutual inductance type AC susceptometer. Magnetization 
measurement was performed using a Vibration Sample Magnetometer (Lakeshore, Model 
7410). 
3. Results and discussions 
Room temperature XRD pattern (Figure 1) of Ni48Fe20Ga32 alloy showed a two phase 
structure. All the peaks were indexed to y (fee austenite) and P (body centred tetragonal 
martensite) phase, respectively. XRD peaks were simulated for fee and bet structures 
using the Powder Cell program [9,10]. The simulated pattern (dotted lines in Figure 1) 
matched well with the experimental XRD pattern. The calculated lattice parameters were 
a = 5.76 A for the y -phase and a = b = 2.69 A, c - 4.16 A for the P phase, respectively 
The percentage of y -phase and ft -phase was estimated to be about 92% and 8%, 
respectively. An overall composition of Ni4846Fe2023Ga3121 was obtained from SeM-EDS 
analysis. 
Figure 1. XRD (solid line) and simulated (dotted Figure 2. Optical micrograph of Ni48Fe20Ga32 at low 
lines) patterns of Ni^Fe^Ga^ alloy. magnification. 
Figure 2 shows weak surface relief features in Ni48Fe20Ga32 alloy, which is indicative of 
the residual (8%) martensite phase present in the sample at room temperature. 
Figure 3 shows the temperature dependence of ac susceptibility of the alloy in a 
magnetic field of 16 Oe (kA/m). the sharp decrease in ac susceptibility around 322 K 
signifies the transition from low temperature ferromagnetic phase to high temperature 
paramagnetic phase. The Curie temperature was found to be 326 K. Thermal hysteresis 
observed during the heating and cooling cycles was negligible as shown in Figure 3. 
Magnetic and martensitic transformations in Ni-Fe-Ga alloy 171 
However, a clear thermal hysteresis was observed in the ACS data between 228 K 
and 244 K as shown in Figure 4. This is a signature of the martensitic (while cooling) and 
reverse martensitic (while heating) transformations occurring in the alloy The drastic change 
1000 
f 800-I 
1 600 
$ 400-J 
3 (/) 
< 200 
IT 
-•—Heating 
o - Cooling 
" ^ X J U . 
300 310 320 330 340 350 360 
Temperature (K) 
Figure 3 Variation in ac susceptibility with temperature from 325 K to 360 K 
in the ac susceptibility and the thermal hysteresis are characteristics of these 
transformations The irreversibility between the heating and cooling cycles is attributed to 
the free energy minima corresponding to the parent phase and product phase, which are 
separated by energy barrier [11] The martensitic start temperature {Ms) and martensitic 
finish temperature (Mf) are marked in the cooling cycle, whereas the reverse martensitic 
start temperature (As) and reverse martensitic finish temperature (Af) are marked in the 
heating cycle of the ACS data shown in Figure 4 Only one structural transformation, 
corresponding to the low temperature martensite phase was observed in the ACS studies 
in the temperature range of 200 K to 475 K The room temperature martensite phase 
observed in the XRD pattern and the optical micrograph could not be characterized since 
it did not show any transformation in the ACS studies in the temperature range of 200 K 
0018 
- A - Heating 
220 240 
Temperature (K) 
260 
Figure 4. Variation in ac susceptibil ity with 
temperature from 205 K to 260 K 
0 5 10 15 
Magnetic field (kOe) 
Figure 5. Initial magnetization curve for 
Ni48Fe^0GaJ2 alloys (up to 20 kOe) 
172 M Raghusankar, Sidananda Sarma, S Ravi and A Snmvasan 
to 475 K. This weak room temperature martensite phase might have resulted due to 
inhomogeneities in the as-cast sample. 
The variation of magnetization (M) with applied field (H) is shown in Figure 5. The 
saturation magnetization of this sample was found to be 18 emu/g at 200 kOe 
Ni48Fe20Ga32 alloy has a ferromagnetic martensitic phase below 240 K. Heat treatment 
of Ni-Mn-Ga alloy resulted in an increase in the martensitic transformation temperatures 
[10] and also improved the homogeneity of the alloy It would be interesting if a similar 
trend could be observed in this alloy If so, this would provide a means to obtain a room 
temperature ferromagnetic martensitic phase in this alloy 
4. Conclusion 
Ferromagnetic behavior was observed above the room temperature (up to 326 K) whereas 
the martensitic phase existed only below 240 K in as-cast Ni48Fe20Ga32 alloy. Heat 
treatment would ensure better homogenization of the as-cast ingot and might help in 
raising the reverse martensitic start temperature well above the room temperature in this 
FSMA 
Acknowledgment 
P K Nayak and S K Snvastava are acknowledged for their help with the low temperature 
ACS measurements 
References 
[1] K Ullakko J K Huang C Katner, R C O'Handley and V V Kokorin Appl Phys Lett 69 1966 (1996) 
[2] H Monto, A Fujita, K Fukamichi R Kainuma, K Ishida and K Oikawa Appl Phys Lett 83 499T 
(2003) 
[3] K Oikawa, T Ota, Y Sutou T Ohmon R Kainuma and K Ishida Mater Trans 43 2360 (2002) 
[4] H Monto, A Fujita, K Fukamichi, T Ota, R Kainuma, K Ishida and K Oikawa Mater Trans 44 661 
(2003) 
[5] Y Murakami, D Shmdo and K Oikawa Appl Phys Lett 82 3695 (2003) 
[6] Y Sutou, N Kamiya, T Omon, R Kainuma and K Ishida Appl Phys Lett 84 1275 (2004) 
[7] Z H Liu M Zhang, Y T Cui, Y Q Zhou W H Wang, G H Wu, X X Zhang and G Xiao Appl Phys 
Lett 82 424 (2003) 
[8] S Sarma, M P C Kalita, A Perumal and A Snnivasan Proc Natl Workshop Adv Tech Mater 
Charac, Vadodara p 19 (2006) 
[9] W Kraus and G Nolze J Appl Cryst 29 301 (1996) 
[10] www ccp14 ac uk 
[11] S Majumdar, V K Sharma, R Kaul, S B Roy and P Chaddah Solid State Commun 136 85 (2005) 
[12] J Pons, C Segui, V A Chemenko, E Cesan, P Ochin and R Portier Mater Sci Engg A273 315 
(1999) 


Magnetic and Martensitic Transformations in Ni-Fe-Ga Alloy

Gogoi, Purabi

Ansari, Taufique A

Agarwal, Pratima

Indian J. Phys. 82 (2), 179-184 (2008) 
Steady state photo carrier grating technique for 
measurement of charge carrier diffusion length 
Purabi Gogoi*, Taufique A Ansari and Pratima Agarwal 
Physics Department, Indian Institute of Technology, 
Guwahati-781 039, Assam, India 
E-mail purabig(fMitgernet in 
Abstract . Steady State Photo carrier Grating technique (SSPG) is fabricated to measure the charge carrier 
diffusion length In semi conducting thin films The experiment is carried out in some hydrogenated amorphous 
silicon and silicon germanium alloys, the values of diffusion length are found to be in good agreement with 
literature 
Keywords • Amorphous silicon, silicon germanium alloys, diffusion length, solar cell and photoconductivity 
PACS Nos. : 73.50.Pz, 78.66.Jg, 84 60.Jt 
1. Introduction 
The prior knowledge of carrier diffusion length (Ld) in a semiconductor is very necessary 
in the fabrication and optimization of devices like Solar Cell, Thin Film Transistor etc. 
Especially for hydrogenated amorphous silicon (a-Si:H) and alloys like amorphous silicon 
germanium (a-SiGe:H), the value of diffusion length is a very good indicator of the material 
quality for solar cell application. Hence a number of techniques have been developed for 
the measurement of L^ Haynes-Shockley method, Surface Photo Voltage method (SPV) 
being some of them. Another important method, which is gaining importance, is Steady 
State Photo carrier Grating (SSPG) method originally developed by Ritter, Zeldov and 
Weiser [1]. This is a self consistent and self sufficient [2] and at the same time very 
simple and versatile method for routine characterization of L^ In this paper we report the 
instrumentation of SSPG that we have done in our laboratory and results of some Ld 
measurements carried out for some a-Si:H and a-SiGe:H alloys. 
Corresponding Author 
© 2 0 0 8 I ACS 
180 Purabi Gogoi, Taufique A Ansari and Pratima Agarwal 
2. Theory 
When the two coherent light beams superpose on thin photoconductive film, the resulting 
light intensity on the sample will be modified due to the formation of photo grating according 
to the equation, 
/<*) = (/,+/2) uYo . , 
'1 + / 2 
COS 2nx 
~A~ 0) 
where, ^ and l2 are the intensities of interfering beams A = A/(2sin5/2) is the grating 
period, X is the wavelength of light, 5 is the angle between the two beams, y0 is fringe 
visibility factor 
Carrier 
concentration 
L„<A 
• III II 
U>A 
I. ' J !J I 
(a) - > x (b) 
Figure 1. (a) Light Grating (above) and photo carrier grating (below) and (b) Blurring of Carriers for 
Lfj < A and Ld> ^ 
Due to the formation of photo grating on the sample there will be subsequent formation 
of photo carrier grating (periodic variation of carriers). Because of the formation of low and 
high resistance regions photocurrent perpendicular to the grating fringes will be less than 
the case when there is uniform illumination. After the formation of carrier grating, the 
carriers will diffuse from high concentration region to low concentration region. If the diffusion 
length (LJ is less than the grating period (A), carrier grating will persist in the sample 
and in the other case carrier grating will blur resulting uniform concentration 
If l2 < lv one can solve the diffusion eqs. [1, 3] to get the photoconductivity as, 
a(x) = a(/1+/2) « A (2nx) 1 + A cos — (2) 
where, A = 2ay0y / 1-^- and Y 
Ci+'2) uf** L*y 
Steady state photo carrier grating technique etc 181 
„ _ Exponent of power law dependency of aph with light intensity, y0 = grating quality 
factor. 
The average conductivity perpendicular to the grating fringes og will be, 
og=Al i[*k*°^u*-* (3) 
The parameter /3, which is the ratio between the photocurrent in the presence and 
absence of grating, is related to A and Ld as, 
0 = ^ = 1- 2<p/(l + 4n2L2d/A2f (4) 
where, 0 = ay* 
A little bit of modification of the eq (4) shows that a plot between l / , \2 vs ^2/1 - /i 
gives, intercept = -l/(27rL^)2 and slope =y0a05/(2^Lc/)2 , from where L^and y can be 
found out 
3. Instrumentation and Experimental 
Figure 2 shows the schematic diagram of SSPG set up for the measurement of carrier 
diffusion length. The randomly polarized monochromatic light from a laser source (633 
nm) is split into two coherent beams with the help of a beam splitter, which are then 
reflected by two mirrors in Mczhender geometry and then allowed to superpose on the 
sample The photograting is created by using two polarizers in the path of the beams 
which are in same state of polarization (P1 and P2), whereas for uniform illumination 
instead of P2, another polarizer P3 (cross polarized) is used. In order to measure the 
Beem Splitter 
| HsNs Laser f 
Polinzer Pt 
Figure 2. Schematic diagram for diffusion length measurement by SSPG 
182 Purabi Gogoi, Taufique A Ansari and Pratima Agarwal 
carrier diffusion length, we modulate the optical grating on a uniformly illuminated 
background and measure the change in photoconductivity due to diffusion of carriers using 
an optical chopper and lock-in amplifier. We use one ND filter to reduce the intensity of 
the chopped beam to 10% of the other beam. The signal is fed to the lock in amplifier 
(LA) across a load resistance (RL). Hence the signal monitored by the LA will be 
proportional to og (r(l^) when there is grating formation and cr(/1 + /2)-cr(/1) when there 
is no grating. So, 
fi~-
G« <x(/i) 
tf(/i+/2)-<r('i) 
(5) 
This experimental parameter /? is measured as a function of A by varying the angle 
between the beams This is done by rotating the mirrors. For easy and precise movement 
of the mirrors they are mounted on gymble mounts. 
4. Results and discussions 
We have performed the SSPG experiment on some hydrogenated amorphous silicon 
(prepared by PECVD technique from precursor gas SiH4) and silicon germanium alloys 
(prepared by PECVD, precursor gases Si2H6 and GeH4). The values of diffusion length we 
have got are in agreement with literature. Table 1 gives the deposition condition and 
Table 1. Deposition conditions and Lrf values for a-SiGe H films 
Sample R l f- Thickness Band gap H Cone 
\Si2He\ (jim) (eV) (%) 
(X Yo Ld(nm) 
GD 357 
GD 359 
GD361 
0 72 
0 36 
0 00 
0 7 
0 7 
07 
1 48 
1 65 
1 84 
98 
142 
164 
0 57 
0 76 
0 82 
0 99 
1 0 
0 96 
105 
126 
140 
400 600 800 1000 1200 1400 1600 
A (nm) 
Figure 3. p- \ curve for a-SiGe H films 
Steady state photo carrier grating technique etc 183 
diffusion length of some of the a-SiGe:H films. Figure 3 shows the /? vs A curve while 
Figure 4 shows the l / / \2 vs sqrt {2/(1 - /?)} curve for the films. Though we have reported 
here only the results of a-SiGe:H films in details, other series of films (a-Si:H) also show 
diffusion length around 100 nm. 
8 0x10-7H 
4 0x10-
sqrt (2/(1-
Figure 4. l//A? - j2/(\ -"/*) curve for a-SiGe H films 
While performing the SSPG measurements there are a few points to be taken care of. 
In the first place, because of the difference in the transmittance of the polarizers', intensity 
of weak beam may be different depending on whether it is crossed polarized or same 
polarized. So it is very important to ensure that the intensity of the weak beam is the 
same in both the cases. This ensures that the difference in photocurrent is coming from 
the actual formation of grating and it is not an artifact. Secondly, one beam should be 
much weak compared to the other; the theory is valid for that approximation only. Otherwise 
large modulation of carrier concentration will cause band bending, which makes the 
transport drift limited. Another important point is that the bias voltage should be sufficiently 
small so that conductivity comes from diffusion of carriers only and not from drift. We put 
the polarizers after the mirrors to avoid the mirror-induced polarization. The load resistance 
(RL) has also to be optimized so as to get good signal and at the same time it should 
not modify the current in the circuit. The theory presented here is valid for insulating films 
(dark conductivity negligible compared to photoconductivity). For films having good dark 
conductivity, the theory has to be modified and the effect of dark conductivity has to be 
taken into account [4]. 
5. Conclusion 
In this paper we have presented a simple and versatile technique for the charge carrier 
diffusion length measurement. This technique further can be used for the density of state 
determination in semiconductors [5]. 
184 Purabi Gogoi, Taufique A Ansari and Pratima Agarwai 
References 
[1] D Ritter, E Zeldov and K Weiser AppI Phys Lett 49 791 (1986) 
[2] I Balberg, A E Delahoy and H A Weakliem AppI Phys Lett 53 992 (1988) 
[3] D Ritter, K Weiser and E Zeldov J AppI Phys 62 4563 (1987) 
[4] E Sauvain and J H Chen J AppI Phys 75 5191 (1994) 
[5] J A Schimdt and C Longeaud Phys Rev B71 125208 (2005) 


Steady State Photo Carrier Grating Technique for Measurement of Charge Carrier Diffusion Length

From Editor's Desk

Indian J. Phys. 82 (3), 365-366 (2008) 
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Kolkata-700 098, India 
Probir Roy, Indian 
High Energy Physics Division, 
Tata Institute of Fundamental 
Research, * Homi Bhabha Road, 
Colaba, Mumbai-400 005, India 
G P Das, Indian 
Materials Science Department, 
I.A.C.S., Jadavpur 
Kolkata-700 032, India 
J K Datta Gupta, Indian 
Saha Institute of Nuclear Physics, 
1/AF, Bidhan Nagar, 
Kolkata-700 064, India 
B G Ghosh, Indian 
Saha Institute of Nulcear Physics, 
1/AF, Bidhan Nagar, 
Kolkata-700 064, India 
Asok Sen, Indian 
Saha Institute of Nulcear Physics, 
1/AF, Bidhan Nagar, 
Kolkata-700 064, India 
Avijit Sen, Indian 
Institute for Plasma Research, 
BHAT, 
Gandhmagar-382 424, India 
T P Singh, Indian 
Biophysics Department, 
All India Institute of Medical 
Science, Ansari Nagar, 
New Delhi-110 029, India 
P K Mukherjee, Indian 
Spectroscopy Department, 
I.A.C.S., Jadavpur, 
Kolkata-700 032, India 
6. Name and Address of Nil 
individuals who own the 
shareholder holding more than 
one percent of the total capital 
I, Mr Swapan Kumar Mukherjee, hereby declare that the particulars given above are true to the 
best of my knowledge and belief. 
Dated : March 3, 2008 
Sd/-
(Swapan Kumar Mukherjee) 
Signature of Publisher 


Form IV

Front Title

Chattaraj, P K

Giri, S

•Erratum 
Indian J. Phys. 82(4) 467-468(2008) 
Erratum 
A minimum electrophilicity perspective of the HSAB principle 
P K Chattaraj* and S Giri 
Department of Chemistry, Indian Institute of Technology, Khargpur, Kharagpur-721 302, West Bengal, India 
[Indian J Phys. 81 (9), 871-879 (2007)] 
As desired by the Authors following changes (on accepted version) be made on their paper 
leferred to as an "Erratum" 
The changes are as follows 
SI. No. 
1. 
2. 
3. 
4. 
5. 
Page Nos. (with location) 
Page no. 871 - line 8 (from bottom) 
Page no. 871 - line 12 (from bottom) 
Page no. 873 - line 1 
(from top at the end) 
Page no. 873 - line 6 (from top) 
Page no. 874 - Table 2 
(column 2, line 5 from top) 
(column 3, line 10 from top) 
(column 5, line 15 from top) 
(column 7, line 5 from top) 
(column 7, line 10 from top) 
(column 7, line 15 from top) 
Please read as 
values 
electrons to 
((Ov/dfcO)) 
[12(d); 16 (b,d)] 
2.2051 
3.7804 
3.5681 
0.4214 
0.2550 
0.3101 
Instead of 
value 
electron 
((cVtfy)=0)) 
[12(d), 16(b)] 
2.2149 
2.2038 
2.043 
0.4312 
1.8316 
1.2150 
'Corresponding Author <D 2006 IACS 
468 
SI. No. Page Nos. (with location) 
6. Page no. 875 -Table 2 (contd.) 
(column 2, line 10 from top) 
(column 2, line 14 from top) 
(column 2, line 27 from top) 
(column 2, line 29 from top) 
(column 4, line 13 from top) 
(column 4, line 14 from top) 
(column 4, line 15 from top) 
(column 7, line 10 from top) 
(column 7, line 14 from top) 
(column 7, line 27 from top) 
(column 7, line 29 from top) 
Please read as 
3.7804 
4.8480 
-175.5410 
3.4263 
5.1563 
4.5258 
2.9373 
-0.0467 
0.7238 
-0.2348 
2.3212 
Instead of 
2.2038 
4.8156 
-175.5400 
3.3920 
5.156295 
4.507881 
2.937287 
1.5299 
0.7382 
-0.2358 
2.3554 
Page no. 876 - Table 5 
(column 4, line 8 from top) 1060.255 -1060.300 
8. Page no. 877 - Table 6 
(column 1, foot note) 
(column 4, line 33 from top) 
(column 7, line 5 from top) 
(column 7, line 26 from top) 
9. Page no. 878 - Reference no. 
at the end 
[6] 
To be shifted to 
the bottom of the 
Table 2 
4.9196 
0.0240 
0.0496 
107 PR 46 (2007) 
Bottom foot note 
of Table 6 
5.5318 
0.0200 
0.6618 
(2007) (in press) 
The main conclusion of the paper remains the same. 


Erratum: A Minimum Electrophilicity Perspective of the HSAB Principle

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