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51.
Electronic states of the PbSi molecule up to 4 eV have been studied by carrying out ab initio based MRDCI calculations which include relativistic effective core potentials (RECPs) of both the atoms. The use of semicore RECPs of Pb produces better dissociation limits than the full-core one. However, the (3)P(0)-(3)P(1) splitting due to Pb is underestimated by about 4000 cm(-1). At least 25 bound electronic states of the Λ-S symmetry are predicted for PbSi. The computed zero-field-splitting in the ground state is about 544 cm(-1). A strong spin-orbit mixing changes the nature of the potential energy curves of many Ω states. The overall splitting among the spin components of A(3)Π is computed to be 4067 cm(-1). However, the largest spin-orbit splitting is reported for the (3)Δ state. A number of spin-allowed and spin-forbidden transitions are predicted. The partial radiative lifetime for the A(3)Π-X(3)Σ(-) transition is of the order of milliseconds. The computed bond energy in the ground state is 1.68 eV, considering the spin-orbit coupling. The vertical ionization energy for the ionization to the X(4)Σ(-) ground state of PbSi(+) is about 6.93 eV computed at the same level of calculations. 相似文献
52.
Arup Bandyopadhyay 《Pramana》2002,59(6):933-939
Variable Energy Cyclotron Centre (VECC) is presently developing an ISOL post-acclerator type of RIB facility. The scheme utilises
the existing K=130 room temperature variable energy cyclotron machine as the primary accelerator for the production of RIBs and radio frequency
quadrupole (RFQ) and LINAC modules for the post-acceleration. The design aspects of these post-accelerator LINAC modules will
be discussed in this paper. 相似文献
53.
The electrical resistivity of bulk Ge20Te80 has been measured as a function of pressure and temperature. At 5 GPa, an amorphous semiconductor-to-crystalline metal transition
has been observed. The sample recovered from the high pressure cell, after the application of 7 GPa, has a face-centred cubic
structure with a lattice constant of 6·42 A. In crystalline sample, the semiconductor-to-metal transition occurs at 7 GPa.
The thermoelectric power has also been measured for glassy samples in the temperature range 300–240 K. 相似文献
54.
Electrical resistivity studies of the charge transfer complex benzidine—TCNQ and its inclusion compound, have been carried
out up to pressures 8 GPa. Two types of behaviour were observed in these complexes under high pressure and this difference
is interpreted and discussed. 相似文献
55.
56.
A.K. Bandyopadhyay F. Beuneu L. Zuppiroli M. Beauvy 《Journal of Physics and Chemistry of Solids》1984,45(2):207-214
Boron carbide is a ceramic which has a wide field of application because of its mechanical and nuclear properties. This material is difficult to characterise due to the presence of different levels of disorder and inhomogeneities which are found in the usual available samples. The transport and magnetic properties of several samples of boron carbide have been measured from liquid helium to room temperature as a function of temperature and composition. We have attempted to attribute the different features of these properties to the different levels of disorder. The role of free carbon, in form of thin layers of graphite within the disordered semi-conducting matrix, was investigated in particular details, because it was either ignored or neglected by others. Free carbon is found to dominate the D.C. transport when its concentration is larger than 5%; while the principal features of the electron spin resonance (E.S.R.) line show a dominance of free carbon when the concentration is larger than 3.5%. Below these concentrations conductivities as well as spin relaxation rates do not depend very much on free carbon; neither these have been found to be correlated in a simple way to the stoichiometry: the disorder in the boron sublattice is probably responsible for the electronic properties in this range of concentrations. 相似文献
57.
The problem of nonlinear optimization is encountered while fitting the observed response of certain radiation detectors. In
this paper the development of an optimizing technique based on quasi random search is described. The performance of this technique
is compared with other existing methods of gradient search and linear Taylor differential correction technique in the case
of fitting the photopeak responses of Nal(Tl) detectors. Our results are favourable especially when the observed data are
associated with poor statistics. 相似文献
58.
A study of effective implementation of threshold activation technique for neutron spectral analysis in the environment of
an alpha-cyclotron target is presented. The activation data are analysed using LOUHI-82 code. Optimal choices of the regularization
parameters of the code are studied and discussed. Energy distribution of neutrons emitted from thick targets of Be, C and
Ta irradiated by 40–45 MeV alphas is discussed. 相似文献
59.
Jorgen Rassing Saibal Bandyopadhyay Edward M. Eyring 《Journal of Molecular Liquids》1983,26(2):97-108
A new sample cell construction for a light diffraction method permits absolute measurements of the ultrasonic absorption coefficient for a strongly absorbing transparent gel. By means of this cell the absorption coefficient at 6.2 MHz has been measured as a function of the temperature in the gelling temperature range for a 25% (w/w) aqueous solution of the ABA polyoxyethylene-polyoxypropylene block copolymer PLURONICR F 127. The resonator method has been used under the same experimental conditions. The strongly absorbing gel causes overlapping of the resonance signals. A calibration based on resonance experiments compared with the absolute measurements yields a solution to that problem and thus makes the resonator method applicable to a strongly absorbing gel. 相似文献
60.
Pratul Bandyopadhyay Brahmananda Bhattacharya Harish Sarkar 《International Journal of Theoretical Physics》1983,22(8):677-689
In quantum neutrinodynamics (photon-neutrino weak coupling) all the renormalization constants vanish and therefore the field equations cannot be expressed in terms of unrenormalized field quantities. This helps us to formulate quantum neutrinodynamics as a convergent quantum field theory. It is also pointed out that from the viewpoint of the unified model of weak and electromagnetic interaction as developed on the basis of the photon-neutrino weak coupling by Bandyopadhyay, quantum electrodynamics also manifests itself as a convergent field theory. 相似文献