Photostimulated kinetic effects in semiconductors

It is shown that the presence of intense laser radiation can result in the origination of spreading of kinetic effects even in a degenerate monopolar semiconductor with an isotropic energy spectrum, where the magnitude of such photostimulated effects can exceed the magnitude of corresponding effects in the absence of radiation, due to the thermal spread of current carriers in the energies or anisotropies of isoenergetic surfaces. Photostimulated Ettingshausen, Peltier, and transverse magnetoresistive effects are considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 121–129, February, 1976.     

Calculation of the vibration–rotational transition intensities of water molecules trapped in an argon matrix: stretching O–H vibrations spectral region

The frequencies and intensities of vibration–rotational transitions of water molecules in an argon matrix were calculated for temperatures of 6 and 30 K. The rigid asymmetric top approximation was used with available literature values of the effective rotational constants in the ground and excited vibrational states. The calculations were carried out by taking into account the existence of a non-equilibrium population distribution between the rotational levels of ortho- and para-water isomers. It was assumed that the temperature relaxation of the population of rotational levels is independent of the ortho- and para-isomers. Comparison of the results of the theoretical calculations with experimental literature data shows good agreement for the majority of the rotational structure lines for symmetric and antisymmetric stretching vibrations both in the frequency values and in the values of the relative intensities.     

Barriers to internal rotation and tunnelling splittings of the torsional states in the HO(CH2)OH,DO(CH2)OH and DO(CH2)OD molecules

Torsional states caused by vibrations of hydroxyl groups in the methanediol molecule and its two deuterated analogues – DO(CH₂)OH and DO(CH₂)OD were analysed at MP2/cc-pVTZ and CCSD(T)/cc-pVQZ levels of theory. In the first case, 2D PES and 2D surfaces of kinematic coefficients were calculated with geometry optimisation for all other geometric parameters, and in the second case, only the energy of optimised configurations at the MP2/cc-pVTZ level of theory was determined. Then 2D PES was recounted to the complete basis set (CBS) limit by extrapolating the results of calculations at the MP2/cc-pVTZ and MP2/cc-pVQZ levels of theory The calculated values were then averaged over four equivalent points on the coordinate plane. Hamiltonian matrices were constructed using DVR and Fourier methods. After their subsequent diagonalization, the energies of the stationary torsional states were computed. Their classification by C_2V(M) and C_S(M) molecular symmetry groups has been performed. The splitting values due to the tunnelling of the thirty most deeply located torsional states in the three studied molecules were also determined. The torsional states, internal rotation barriers, and tunnelling frequencies in the molecules of methanediol and hydrogen trioxide were compared.     

Excitation of terahertz surface polaritons in a cylindrical waveguide by femtosecond laser pulses

Generation of terahertz surface polaritons in homogeneous round cross-section plasma waveguides upon nonlinear optical rectification of femtosecond laser pulses is analyzed theoretically. It is assumed that nonlinear polarization inducing a surface electromagnetic wave is formed at the waveguide boundary in a thin layer of the nonlinear dielectric that surrounds the waveguide. The efficiency of the femtosecond radiation conversion into surface polaritons is studied as a function of the waveguide radius and duration of the exciting laser pulse.     

Melting of nanocrystals embedded in a crystal matrix heated by nanosecond laser pulses

The kinetics of phase transformations of nanocrystals in a crystal matrix is considered upon non-stationary heating by laser pulses. The melting and crystallization kinetics of nanocrystals is described taking into account their size, shape, elemental composition, and elastic deformations appearing due to the mismatch of the lattice constants for nanocrystals and the matrix. The possibility of decreasing the dispersion of nanocrystals over their size in heterostructures with quantum dots is predicted. As an example, melting of Ge nanocrystals in a Si matrix is considered.     

On Focusing of Broadband Terahertz Pulses

Optics and Spectroscopy - The particular features of the focusing of a broadband THz pulse with a Gaussian transverse amplitude distribution by a lens are investigated theoretically. The...     

Investigation of platinum oxide-titanium films by the method of X-ray photoelectron spectroscopy

Platinum oxide-titanium films that are produced by thermolysis of H₂PtCl₆ in the presence of NO ₃ ⁻ on a titanium surface are investigated by the method of x-ray photoelectron spectroscopy. It is shown that making nitrates a part of the composition leads to an increase in the content of oxidized forms of platinum and the appearance of titanium in the film. Belarusian State Technological University, 13a, Sverdlov St., Minsk, 220630, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 536–538, July–August, 1997.     

Thermodynamics of Aqueous Nitrilotriacetic Acid (NTA) Systems: Apparent and Partial Molar Heat Capacities and Volumes of Aqueous HNTA2−, NTA3−, MgNTA−, CoNTA−, NiNTA− and CuNTA− at 25 °C

Apparent molar heat capacities and volumes have been determined for aqueous Na₂HNTA, Na₃NTA, NaMgNTA, NaCoNTA, NaNiNTA and NaCuNTA at 25 °C. The experimental results have been analyzed in terms of Young’s rule with an extended Debye–Hückel equation to obtain standard partial molar heat capacities C _p ^o and volumes V ^o for the species HNTA²⁻(aq), NTA³⁻(aq), MgNTA⁻(aq), CoNTA⁻(aq), NiNTA⁻(aq) and CuNTA⁻(aq), at ionic strengths I = 0 and I = 0.1 mol⋅kg⁻¹. Values of C _p ^o and V ^o were combined with the literature data to estimate the stability constants of the NTA complexes at temperatures up to 100 °C.