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991.
Nonparabolicity of the heavy hole band in diamond-like semiconductors, which occurs within the framework of the three band model with the perturbation from the other bands taken into account to the Löwdin prucedure, is studied. A direct dependence of nonparabolicity on the band anisotropy (caused by the different effect of 15c and 12c bands) and the inverse dependence on the magnitude of the spin-orbit splitting is established. A connection between the effective mass of heavy holes and their energy is obtained, which is valid for the majority of diamond-like semicondactors, except for materials with very strong nonparabolicity of the band of silicon type.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 66–70, February, 1987. 相似文献
992.
In the quark-parton model we obtain an expression for the effective cross section of the process of direct photon generation in the annihilation of an antineutrino and an electron into hadrons (e + e + X). The angular and energy dependences of the photons are investigated. It is shown that for large photon energies, the contribution from hadronic radiation dominates that from leptonic radiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 98–103, November, 1987. 相似文献
993.
An original variant of an electronic device is described, which can be used for gamma-process selection under ionized gas conditions. The device is based on a Hanley and Schaffernicht electron gun. Selection of photons and metastable atoms is performed by a quartz tube located in axial symmetry with the primary electron gun. The desired signal is measured from the flow of secondary electrons emitted from Al, Pt, Ag, and Au surfaces under the action of resonant photons radiated from the levels Hg(63P1) and Hg(61P1). For =2537 Å the following values were obtained for ph 9.1, 3.8, 1.1, 0.25. Analogous values of ph for =1850 Å were equal to 45.5, 10.8, 6.5, 3.2. The ph values are in units of 10–4.Translated from Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 68–74, December, 1987. 相似文献
994.
N. K. Morozova Yu. A. Pashchenko V. D. Chernyi V. G. Galstyan T. P. Dolukhanyan V. I. Muratova 《Russian Physics Journal》1987,30(2):143-149
The nature of the luminescence of zinc sulfide in the spectral range (360), 380–420 nm (SAL) at 80K is analyzed. It is shown that the appearance of SAL radiation is accompanied by additional absorption in the region (350) 365–370 nm at 80K. The low-temperature spectra of sphalerite, exposed to different radiation and subjected to different treatment, are studied. The multiband luminescence of the isoelectronic sulfur impurity in ZnO deposits in the region 383–640 nm is discussed. It is concluded that SAL luminescence is attributable to the localization of excitons in ZnS on clusters, whose formation precedes the precipitation of the ZnO·S phase. The formation of oxygen clusters and deposits on dislocations in ZnS is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 60–66, February, 1987. 相似文献
995.
I. K. Andronik V. S. Vavilov Vu Zoan Mien P. G. Mikhalash M. V. Chukichev 《Russian Physics Journal》1987,30(8):702-706
The results are given of studies on the edge emission of undoped and copperdoped ZnTe crystals in the temprature range 4.2–300K. The copper impurity has been found to increase the intensity of the principal edge emission band substantially. Analysis of the structure of this emission band indicated that a temprature below 160K the main role is played by the emission from excitons that are most probably bound in CuZn and LiZn centers while at higher temperatures it is played by emission during the transition of free electrons to these centers. An appreciable role is played over the entire range of temperatures by emission from free electrons with an energy of 13 MeV. The luminescence quenching energy below 160 K has a value of 7 MeV (the binding energy of a bound exciton) and at higher temperatures it is 78 MeV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 68–73, August, 1987. 相似文献
996.
Summary A stop time S in the boson Fock space over L
2()+ is a spectral measure in [0,] such that {S([0,t])} is an adapted process. Following the ideas of Hudson [6], to each stop time S a canonical shift operator U
Sis constructed in . When S({}) has the vacuum as a null vector U
Sbecomes an isometry. When S({})=0 it is shown that admits a factorisation
S]{S
where {S
is the range of U
Sand
S] is a suitable subspace of called the Fock space upto time S. This, in particular, implies the strong Markov property of quantum Brownian motion in the boson as well as fermion sense and the Dynkin-Hunt property that the classical Brownian motion begins afresh at each stop time. The stopped Weyl and fermion processes are defined and their properties studied. A composition operation is introduced in the space of stop time to make it a semigroup. Stop time integrals are introduced and their properties constitute the basic tools for the subject. 相似文献
997.
We prove that the Boolean lattice of all subsets of an n-set can be partitioned into chains of size four if and only if n9.Research supported in part by N.S.F. grant DMS-8401281.Research supported in part by N.S.F. grant DMS-8406451. 相似文献
998.
I. Pelant M. N. Popova J. Hála M. AmbroŽ V. Lhotská K. Vacek 《Czechoslovak Journal of Physics》1987,37(10):1183-1197
Dependence of two-photon absorption (TPA) rate on the state of polarization of a laser beam is investigated in the low-temperature orthorhombic modification of Hg2Cl2 crystals. Theoretical calculations of the dependence of TPA rate on the direction of polarization vector of the beam are performed for centrosymmetric points, Y, Z, T, R andS of the Brillouin zone. The domain structure of real crystals is taken into consideration and it is shown that periodicity of the polarization dependence may indicate whether TPA is due to transitions either at, Y, Z, T orR, S points. The polarization dependence of TPA cannot, however, distinguish between points inside these two groups. Comparison of theory with a low-temperature (T 8·5 K) experimental curve of polarization dependence is discussed. It is shown that the experiment can be explained in main features by a model of noninteracting oriented linear dipoles. Further, on the basis of TPA measurements, a simple energy band structure of Hg2Cl2 is proposed regarding Hg2Cl2 crystal as a linear chain of molecules.The authors express thanks to Dr. . Barta for supplying the Hg2Cl2 crystals, Dr. Z. Bryknar for critical comments and Dr. B. Velický for stimulating discussion. We thank also Dr. V. Kohlová for assistance during measurement. 相似文献
999.
1000.