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991.
The effect of pressure on the 2H and 4H polytype of PbI2 has been investigated by Raman and optical absorption spectroscopy, using the diamond anvil cell. The 2H-polytype undergoes
pressure-induced phase transitions at 5 kbar and near 30 kbar. The 4H-polytype exhibits phase transitions near 8 kbar and
above 30 kbar. The Raman modes abruptly change at these pressures. The optical absorption edge shifts red at the rate of 15±1
MeV/kbar in the 2H-PbI2 and at the rate of 7 MeV/kbar in phase II. The latter phase is most likely to possess a 3d-structure and not a layer type.
The possible structures for the high pressure phases are discussed. 相似文献
992.
993.
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995.
P. K. Karmakar S. Chattopadhyay A. K. Sen C. J. Gibbins 《International Journal of Infrared and Millimeter Waves》1998,19(3):493-501
Measurements of rain attenuation over Calcutta have been made using radiometers operating at frequencies of 22.235 and 31.4 GHz. The results have been correlated with observations of rainfall rates made with a fast-response rain gauge. The distributions of peak rain rates over Calcutta for two different years and the cumulative occurrences of rainfall rates and attenuations at the two frequencies are presented. 相似文献
996.
Monte Carlo calculations of hot-electron drift velocity in PbTe and Pb0.8Sn0.2Te at 77 K are reported. The relevant scattering mechanisms together with band-structure nonparabolicity and anisotropy are included in the calculations. A negative differential mobility (NDM) does not appear when the electrons are assumed to remain confined within the L valleys of the conduction band. On the contrary, allowing for electron transfer into the W valleys and taking suitable values of the parameters related to these valleys, an NDM appears and the threshold field for the same agrees well with the experimental data. Alloy scattering in PbSnTe is found to reduce the NDM. 相似文献
997.
C.T. Li M. Vassanji P.K. Chattopadhyay F. Krejs A. Klein 《Physics letters. [Part B]》1977,68(3):209-212
A nonlinear extension of the RPA is proposed and applied to calculate anharmonic effects in the even nickel isotopes. It is shown, by comparison with an exact diagonalization, to be highly accurate. 相似文献
998.
Chattopadhyay P 《Talanta》1995,42(12):1965-1971
Flame atomic absorption spectrometry has been used for the estimation of the alkali metal content (as Na2O and K2O) in 95 reference materials with diverse matrices (including recently introduced Polish and Chinese standard samples awaiting certification through collaborative studies) using 1000 μg ml−1 of lanthanum and 2000 μg ml−1 of rubidium as matrix buffers for sodium and potassium, respectively. The ±t (Student's values for the samples with known recommended values (degree of freedom n − 1 = 9), at the 95% and 99% confidence levels) indicate that within the confidence levels 95–99% there is no statistical difference between the data presented and the reference data for most of the samples. The agreement between the reported data and the results obtained are generally good. 相似文献
999.
Mallick A Haldar B Chattopadhyay N 《Journal of photochemistry and photobiology. B, Biology》2005,78(3):215-221
Steady state absorption and fluorometric techniques have been used to investigate the photophysics of norharmane (NHM), a bioactive fluorophore, in aqueous as well as aqueous cyclodextrin (CD) environments. The absorption and steady state fluorescence spectral studies reveal the formation of two types of inclusion complexes between the fluorophore and beta-cyclodextrin (beta-CD) depending on the relative population of the two. The stoichiometries and association constants of these complexes have been determined monitoring the fluorescence data. alpha-and gamma-cyclodextrin (alpha-CD, gamma-CD) do not have appreciable effect on the spectral pattern of the fluorophore. The differential fluorimetric behavior of NHM in different CD environments has been rationalized from the variation of the relative dimensions of the probe and the CD cavities. 相似文献
1000.
Sourav Pal Keya B. Ghose Hans-Dieter Meyer 《International journal of quantum chemistry》1995,55(3):291-297
In this article, we discuss how to incorporate correlation aspects in the interaction of the electron with a “frozen” correlated target. We discuss the important aspects of correlation for e? + N2 scattering using configuration interaction, coupled cluster, and perturbative methods to describe the correlation in the target molecule. © 1995 John Wiley & Sons, Inc. 相似文献