The pseudorapidity distributions of relativistic singly charged part icles produced in high energy nucleus-nucleus collisions are described by the thermalized cylinder picture. The calculated results are in agreement with the recent experimental data of gold induced interactions at the Brookhaven National Laboratory.

A three-parameter nonlinear model in nonlinear quantum theory,i.e.,the quantized discrete self trapping equation, has been used to calculate the vibrational energy spectrum, including the overtones and combinations with many excited quanta, of AsH stretches of arsine, AsH_{3}. The model calculations agree well with experiment and other calculations. It is shown that the dominant feature of the energy spectrum of AsH_{3} molecule is a pattern of local mode pairs, and that when n≥4, all the vibrational energies are almost localized on a single AsH bond.

The optical-optical double resonant multiphoton ionization (OODR-MPI) technique and the fluorescent excitation spectroscopy technique have been applied to the study of the F′0^{+}_{u} ion-pair state of iodine. This paper presents OODR-MPI spectrum and fluorescent excitation spectrum of I_{2} in the region of 54000-55300cm^{-1} by the three-photon resonant, two-photon ionization (1+2+2) and (1+(1+1)+2) processes.

The effect of an imperfect system on the measurement of squeezing is studied. It is shown that the imperfectly efficient detectors and the unbalance of the beam-splitter will reduce the measured squeezing. The effects on quadrat ure phase squeezing and photon number squeezing are different from the usual balanced homodyne detection.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Within the Tyablikov's theoretical framework, the ground-state property of the two-dimensional antiferromagnetic Heisenberg model on a triangular lattice is studied. Our results show that the sublattice magnetization is M=0.241 and the ground-state energy per bond is E_{g}/ NZJ =-0.166, which are in agreement with the numerical simulations.

The influence of Ga or Si substitution for Co on the structural and magnetic properties of Pr_{2}Co_{17} compounds is investigated. All samples studied here are single phase and have the rhombohedral Th_{2}Zn_{17}-type structure. The unit-cell volume is found to increase linearly by the substitution of Ga for Co,but reduce by the substitution of Si for Co in Pr_{2}Co_{17} compounds. In Pr_{2}Co_{17-x} M_{x}, the Curie temperature decreases monoto nically with increasing at an approximate rate of 153K per Ga atom and 175K per Si atom. The saturation magnetic moment of Pr_{2}Co_{17-x} M_{x} ( M=Ga,Si) decreases with increasing x. The rates of the decrease are larger than that expected as a simple dilution. For Pr_{2}Co_{17-x}Si_{x} ,the spin reorientation transition is observed above room temperature. The spin-reorientation temperature Tsrfirst decreases with increasing Si content and then increases at higher x values (x>2). The spin reorientat ion behavior is interpreted by the competition between the Pr and Co sublattice anisotropies. The easy magnetization direction in Pr_{2}Co_{17-x}Ga_{x} compounds is perpendicular to the c-axis, and no spin reorientation transition is observed.

The magnetic transport properties in granular perovskite system La_{1-x}Sr_{x}MnO^{*}_{3} have been investigated. The spin-dependent inter facial tunneling and the corresponding giant magnetoresistance (GMR) effect have been observed in the whole temperature range below the Curie point T_{c} for the samp les with concentration x from 0.05 to 0.45. Theoretical analysis shows that the interfacial tunneling originates from the difference in magnetism between surfaces and cores, and the tunnel-type GMR stems from the field-induced change of interfacial magnetic order.

Within the framework of the effective-mass envelope-function theory , the field-dependent intersubband optical properties of a Al_{0.4}Ga_{0.6}As/Al_{0.2}Ga_{0.8}As/GaAs step quantum well are investigated theoretic ally based on the periodic boundary condition. A very large Stark shift occurs when the lowest subband electron remains confined to the small well while the hig her subband electron confined to the big well. The optical nonlinearity in a step well due to resonant intersubband transition(ISBT) is analyzed using a density matrix approach. The second-harmonic generation coefficient χ^{(2)}_{2ω} and nonlinear optical rectification χ^{(2)}_{0} have also been investigated theoretically. The results show that the ISBT in a step well can generate very large second order optical nonlinearities,χ^{(2)}_{0} and χ^{(2)}_{2ω} can be tuned by the electric field over a wide range.

8000 CROSSDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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