1,721,168 research outputs found
Metodi per la determinazione spettroscopica di temperature rotazionali e vibrazionali. Applicazione ad un plasma di azoto a bassa pressione
No full textSpectroscopic diagnostics of R.F. discharges at moderate pressures as chemical applications. I. Pure Nitrogen
No full textA vibro-rotational analysis has been performed of the second positive system (SPS) of N2 and of the first negative system (FNS) of N+2 emitted by 35 MHz discharges in flowing nitrogen operated at pressures of 5–50 torr and power densities of the order of 1–10 W-cm-3. The distributions of the vibrational and of the rotational levels follow Boltzmann's law in both the SPS and the FNS with Tv = 4000°K and TR = 2800°K for the N2(C3Πu) state and Tv = 5100°K and TR = 5800°K for the N+2(B2Σ+g) state and independent of pressure. Kinetic gas temperatures are between 1200 and 2000°K and increase with pressure; electron temperatures are in the range 15,000–9,500°K. The reversal of line intensities of the SPS and of the FNS observed with increasing pressure has been tentatively interpreted. Possible chemical implications of these results have been examine
Design, synthesis, structural and thermal characterisation of polymeric chlorocadmate(II) compounds with one-dimensional inorganic chain structures
No full textThe chlorocadmate(II) compounds of formula (Hmepd) [CdCl3] (1) (Hmepd=1-methylpiperidine cation), (H(2)meen)(2)[Cd2Cl8]. H2O (2) (H(2)meen=N-methylethylenediamine dication) and (H(2)amepz) [Cd2Cl6(H2O)(2)] (3) (H(2)amepz=1-amino-4-methylpiperazine dication) are synthesised and their structural and thermal properties investigated. Compound 1 crystallises in space group P2(l)/a. The unit cell dimensions are a=15.046(2), b=10.408(2) and c=6.786(3) Angstrom, beta=92.39(2)degrees, Z=4. The final R value is 0.0353 (Rw=0.0328). Its structure consists of one-dimensional polymeric chains of face sharing CdCl6 octahedra running along the c axis and methylpiperidinium cations. Compound 2 crystallises in the C2/c space group. The unit cell dimensions are a=18.459(2), b=6.986(3) and c=18.167(2) Angstrom, beta=115.95(2)degrees, Z=4. The final R value is 0.0296 (Rw=0.0330). Its crystal structure consists of polymeric chains of [CdCl4](2-) anions running along the b axis, organic cations and non-coordinated water molecules. Compound 3 crystallises in the P2(1)/a space group, with a=7.542(2), b=14.658(4) and c=8.052(2) Angstrom, beta=106.91(3)degrees, Z=2. The final R value is 0.0330 (Rw=0.0340). The crystal structure consists of organic cations and polymeric chains of edge-sharing CdCl5 (H2O) octahedra. In compounds 1 and 2 hydrogen bond interactions between the inorganic chains, the organic cations and the water molecules, if present, contribute to the crystal packing, while in compound 3 this contribution comes from the contacts less than 3.5 Angstrom. The thermal characterisation is also discussed. The structures are compared with other examples of chlorocadmate(II) compounds
Studies of R.F. discharges at moderate pressures and chemical applications. II. Nitrogen-Hydrogen, Nitrogen-Methane and Nitrogen-Hydrogen-Methane Mixtures
No full textSimultaneous vibro-rotational analyses have been carried out for the second positive system (SPS) of N2 (C3Пu − B3Пg), for the violet system (VS) of CN (B2Σ − X2Σ) and for the Swan system (SS) of C2 (d3Пg − a3Пu), emitted by 35 MHz electrical discharges, containing N2, H2 and CH4 flowing mixture s, in the 5–40 torr pressure range and at 1–10 Wcm-3 power densities. The results are consistent with a Boltzman distribution for the rotational levels, but they show a deviation from this law for upper vibrational levels of CN and C2
Spectroscopic measurements of non-equilibrium nitrogen plasmas at moderate pressures
No full textA local vibro-rotational analysis of the excited species, produced in a 35 MHz discharge reactor in flowing nitrogen, has been carried out by measuring radial and axial emission intensities of some vibrational sequences and selected rotational lines of the (0,2) band of the second positive system (SPS) of N2 (C3Πu - B3Πg), in the pressure range 5-35 torr. Radial from lateral band or line emission intensities have been obtained by applying Abel's inversion technique to derive the corresponding vibrational and rotational temperatures with the use of Boltzmann plots. General maps of emission intensities and of vibrational and rotational temperature distributions within the reactor have been drawn. It is shown that a decrease of a factor 103 in the emission intensities from the core to the periphery of the discharge corresponds to a variation in TV and TR of only a factor {reversed tilde equals}2. This result has been interpreted on the basis of the kinetic mechanisms for the excitation and deexcitation of chemical species under discharge conditions. The decrease of V and the increase of TR with increasing pressure are interpreted according to V-R (vibration-rotation) energy-transfer mechanism
Acetals by AlFe-pillared montmorillonite catalysis
No full textAlFe-pillared montmorillonite is an efficient catalyst for acetals preparation in CH2Cl2 at room temperatur
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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