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Synthesis and third-order nonlinear optical studies of four-coordinated Copper(i) complexes
No full textRestricted Access, Proceedings of Optics 2011: Inter national Conference on Light Solid State Physics, 201
Novel triphenylenoimidazole discotic liquid crystals
No full textRestricted Access.A novel discotic core was constructed by fusing imidazole unit with well-known triphenylene discotic core. Two new imidazole fused unsymmetrically substituted triphenylene derivatives were prepared and characterized. While the molecular structures of the new compounds were verified by 1H NMR, UV, MS and elemental analysis, their liquid crystalline properties were determined by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction studies. These triphenylenoimidazole derivatives were found to exhibit hexagonal columnar mesomorphism over a wide temperature range
Development of 1.5 THz waveguide NbTiN superconducting hot electron bolometer mixers
No full textRestricted Access.We present a characterization of a 1.5 THz waveguide niobium titanium nitride (NbTiN) superconducting hot electron bolometer (HEB) mixer which can be pumped by a commercial solid state tunable local oscillator (LO) source. The NbTiN HEB mixer is made from a 12 nm thick NbTiN thin film deposited on a quartz substrate at room temperature. A gold electrode is formed in situ on the NbTiN thin film without breaking vacuum to ensure good contact. The uncorrected DSB receiver noise temperature is measured to be 1700 K at 1.5 THz, whereas the mixer noise temperature is derived to be 1000 K after corrections for losses of the input optics and the intermediate frequency (IF) amplifier chain. The required LO power absorbed in the HEB mixer is evaluated to be 340 nW by using an isothermal technique. The IF gain bandwidth is supposed to be about 1.3 GHz or higher. The present results show that good performance can be obtained at 1.5 THz even with a relatively thick NbTiN film (12 nm), as in the case of 0.8 THz. In order to investigate the cooling mechanism of our HEB mixers, we have conducted performance measurements for a few HEB mixers with different microbridge sizes both at 1.5 and 0.8 THz. The noise performance of the NbTiN HEB mixers is found to depend on the length of the NbTiN microbridge. The shorter the microbridge is, the lower the receiver noise temperature is. This may imply a contribution of the diffusion cooling in addition to the phonon cooling
Nonequilibrium carbon ionization states and the extragalactic far-UV background with He2 absorption
No full textRestricted Access.Using nonequilibrium calculations of the ionic states and the recently calculated extragalactic ultraviolet background radiation with absorption by intergalactic HeII we determine the ratios of CIII to CIV expected at z ∼ 2–3, as functions of metallicity, gas density and temperature. We
constrain the spectrum of the extragalactic ultraviolet background
radiation by fitting the observed abundance ratios carbon ions at these redshifts with those expected from different models of the background radiation. Our analysis of
the observed ratios shows that ‘delayed reionization’ models,
which assume a large fraction of HeII at z ∼ 3, is not favored by data. Our results suggest that HeII reionization was inhomogeneous, consistent with the predictions from recent simulations
Anticlinic smectic C phase in new and novel five-ring hockey stick-shaped compounds
No full textRestricted Access.The synthesis of a new homologous series of novel five-ring compounds composed of hockey stick-shaped
molecules derived from 4-hydroxybiphenyl-3-carboxylic acid which exhibit an interesting sequence of phase transitions
is presented. Uniaxial nematic and smectic A phases, anticlinic smectic C phase and an unidentified smectic
phase at a lower temperature than the latter have been observed. This is perhaps the first example of hockey stick-
-shaped compounds exhibiting anticlinic smectic C phase directly from the isotropic phase. Polarised light optical
microscopy, differential scanning calorimetry, X-ray diffraction measurements and electro-optical switching studies
were carried out to identify the mesophases
Observation of hysteresis in the properties of a ternary lyotropic liquid crystal system
No full textRestricted Access.We have carried out differential scanning calorimetry (DSC), electrical conductivity
and mass diamagnetic susceptibility studies on sodium decylsulfate(SdS)=
decanol=water system for two different concentrations of the constituents. In these
concentrations, this system exhibits calamitic nematic (Nc), isotropic (I) and hexagonal
(H) phases on heating from the room temperature. On heating the samples,
the DSC thermograms exhibit two peaks which can be related to the reported Nc-I
and I-H phase transition temperatures. However, on cooling from a high temperature
they do not exhibit any peak. The temperature dependence of electrical conductivities
and magnetic susceptibilities of these samples are also different while heating
and on cooling. Based on our reported correlation between the susceptibility and
micellar sizes in an ionic micellar system, we infer that the observed hysteresis behavior
in the susceptibility in this system is related to the difference in the temperature
dependence of the micellar sizes on heating and on cooling. The electrical conductivity
in these ternary systems is related to the mobility of the counter ions which
in turn depends on the viscosity of water. Hysteresis seen in the conductivity may
be related to the changes in the viscosity of water due to the difference in the temperature
dependence of the micellar sizes on heating and cooling. Incidentally, in
water based nanofluids, the sizes of the suspended nanoparticles have profound influence
on the viscosity of water
RXTE-PCA observations of 1A 1118--61: timing and spectral studies during an outburst
No full textRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)We report detailed timing and spectral analysis of RXTE-PCA data obtained
from observations during the outburst of a transient X-ray pulsar 1A 1118–61 in
January 2009. The pulse profile showed significant evolution during the outburst and
also significant energy dependence − a double peaked profile upto 10 keV and a single
peak at higher energy. We have also detected quasi-periodic oscillations (QPO) at
0.07–0.09 Hz. The rms value of the QPO is 5.2 % and it shows a significant energy
dependence with highest rms of 7% at 9 keV. The QPO frequency changed from 0.09
Hz to 0.07 Hz within 10 days. The magnetic field strength calculated using the QPO
frequency and the X-ray luminosity is in agreement with the magnetic field strength
measured from the energy of the cyclotron absorption feature detected in this source.
The 3-30 keV energy spectrum over the 2009 outburst of 1A 1118–61 can be well
fitted with a partial covering power-law model with a high energy cutoff and an iron
fluorescence line emission. The pulse phase resolved spectral analysis shows that the
partial covering and high energy cutoff model parameters have significant changes
with the pulse phase
4-(Benzyloxy) phenyl 4-hexadecyloxy-3-methoxybenzoate
No full textOpen Access.In the title compound, C37H50O5, the central benzene ring
makes dihedral angles of 39.72 (14) and 64.43 (13) with the
benzyl and 3-methoxybenzoate rings, respectively. The crystal
structure is stabilized by intermolecular C—H interactions
involving the central benzene ring and the benzene
ring closest to the aliphatic chain
Discovery of a novel ferrielectric phase of five-layer periodicity in binary mixtures of chiral smectic liquid crystals exhibiting unusual reversed phase sequence
No full textRestricted Access.In a binary mixture system of ferroelectric and antiferroelectric liquid crystals whose major component shows an
unusual reversed phase sequence of SmC∗A(1/2) − SmC∗, a new phase with ferrielectric order of five layers has
been discovered by the electric field-induced birefringence (EFIB) measurements. The EFIB was measured using
a photo-elastic modulator (PEM) set-up and by applying an in-plane electric field to a homeotropic aligned cell
filled with the binary mixtures of compounds with ferroelectric and antiferroelectric compounds. The contours
of constant birefringence in the electric field–temperature (E–T) phase diagrams clearly indicate a distinct region
corresponding to a new phase bordering the four-layer SmC∗(1/2) on the low temperature side and SmC∗α on
the high temperature side. This new phase is unambiguously assigned to SmC∗(3/5) whose structure has been
calculated by Osipov and Gorkunov
Synthesis, characterization and third-order nonlinear optical studies of copper complexes containing 1,10-phenanthroline-5,6-dione and triphenylphosphine ligands
No full textRestricted Access.This research article describes the synthesis, characterization and third-order nonlinear optical studies of copper(I) complexes [Cu(Br)(N,N'-C(12)H(6)N(2)O(2))(PPh(3))] and [Cu(I)(N,N'-C(12)H(6)N(2)O(2))(PPh(3))] abbreviated as [CuBrLPPh(3)] (1) and [CulLPPh(3)] (2) (L= 1,10-phenanthroline-5,6-dione). Nonlinear optical properties of the complexes are investigated at 532 nm using single beam Z-scan and degenerate four-wave mixing (DFWM) techniques employing nanosecond laser pulses. The complexes show optical limiting behaviour due to "effective" two-photon absorption. The values of the effective two-photon absorption (2PA) coefficients (beta), third-order nonlinear susceptibilities (chi((3))), and figures of merit (F), are calculate