Trends in electronic-transition chemical lasers

A new class of chemical lasers based on electronic transitions of atoms, radicals, or molecules excited via oxidation chain reactions in the presence of catalysts is proposed and discussed. The possibility is considered of using these processes to realize four lasing schemes: directly via transitions of excited intermediate products, in an exchange chemical laser, using narrowband chemical lamps, and in chemical-excimer lasers. A number of specific active mixtures are proposed. The gain of a realizable chemical Na-BaOlaser is calculated. The possibility of using chemical reactions with participation of cluster molecules are analyzed. The use of atoms as acceptor (emitting) particles is discussed. Two methods of obtaining increased atom densities are proposed. Certain possibilities of obtaining cw lasing on self-limiting atom transitions are considered.This preprint is the text of a paper delivered at the 3rd International Conference on Trends in Quantum Electronics, Bucharest, 29 August-3 September 1988.Translated from Preprint No. 36 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.     

New Solvate Polymorphs of Lanthanide Trisacetylacetonates: Crystal Structures of [Ln(acac)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>] · Solv (Ln = Eu,Dy; Solv = Thf,H<Subscript>2</Subscript>O + EtOH,MeOH)

Solvate polymorphs of [Dy(acac)₃(H₂O)₂] · Thf, [Ln(acac)₃(H₂O)₂] · H₂O · EtOH (Ln = Eu, Dy) and [Dy(acac)₃(H₂O)₂] · 1.5MeOH, which belongs to a new structural type, are isolated as single crystals. The structures of the prepared compounds are determined by X-ray crystallography, and the effect of solvate molecules on their crystal structures is discussed.     

A quantum-chemical study of the possibility to synthesize nuclear spin isomers of water by homogeneous catalytic hydrogenation of compounds containing semipolar X → O bonds (X = N,P, S) with hydrogen

The mechanism of catalytic hydrogenation of compounds with semipolar bonds R_nX → O (R_nX = N₂, Me₂S, C₅H₅N, and Ph₃P) on the (Ph₃P)₃RhCl Wilkinson catalyst with para-hydrogen was modeled quantum-chemically by the density functional theory method with the gradient-corrected nonempirically constructed PBE functional and the TZ2p basis set. The reaction was shown to involve a reaction channel in which the sequential transfer of two hydrogen atoms to oxygen occurred intramolecularly in the coordination sphere of rhodium with the conservation of the spin correlation of protons. This opens up the possibility in principle of using this reaction to prepare para-H₂O, one of the nuclear spin isomers of water in which proton spins are antiparallel.     

Natural oscillations of multidimensional systems nonlinear in the spectral parameter

A new method of solving the generalized vector self-conjugated Sturm-Liouville boundary value problems with the boundary conditions of the first kind is proposed and developed. The iterative algorithm is based on a constructive procedure of introduction of a small parameter and an efficient correction of the desired eigenvalue. The matrix coefficients of the equations are assumed to be nonlinearly dependent on the spectral parameter. The criterion of proximity is introduced, and it is shown that this method has an accelerated convergence of the second order with respect to a small parameter for a reasonably close initial approximation. Test examples are considered.     

Elastic properties of the Ta–V system: bcc Ta0.33V0.67 and C15 TaV2

Resonant ultrasound spectroscopy was used to measure the elastic constants of bcc Ta_0.33V_0.67 over the temperature range 3.5–300?K; the results were compared to earlier measurements on C15 TaV₂. The temperature dependence of the polycrystalline shear modulus is completely different in the two phases; that of the bcc phase decreases with temperature whereas that of the C15 phases increases in an anomalous fashion. This difference is consistent with a model involving doubly-degenerate levels at the X point of the Brillouin zone in the C15 phase with the Fermi level lying near the doubly degenerate level. This model accounted for the unusual behaviour of the C15 phase. Debye temperatures were determined from the ultrasonic measurements: 295?K for the C15 phase and 315?K for the bcc phase.     

Laser excitation of long-lived oscillatory states in a dusty-plasma trap

Vertical oscillations of a single particle in a monolayer dusty-plasma sheath have been excited by a laser radiation pulse. The particle oscillates in a self-sustained regime at a characteristic frequency of about ?? = 25 Hz. It is established that phenomena related to the particle recharge and the delay of its charge variation relative to the equilibrium value cannot account for the self-sustained regime of oscillations. It is suggested that the experimentally observed vertical auto-oscillations of a single particle take place due to resonant pumping of the kinetic energy of the chaotic motion of particles in the dusty-plasma sheath to the energy of vertical oscillations.     

Mononuclear Transition Metal Cymantrenecarboxylates as Precursors for Spinel-Type Manganites

Novel mononuclear cymantrenecarboxylate complexes of transition metals, [Co(H₂O)₆](CymCO₂)₂·4H₂O (Cym = (η⁵-C₅H₄)Mn(CO)₃) (1), [Ni(H₂O)₆](CymCO₂)₂·4H₂O (2), [Zn(H₂O)₆](CymCO₂)₂·4H₂O (3), [Co(CymCO₂)₂(imz)₂] (imz = imidazole, 4), [Co(CymCO₂)₂(bpy)₂]·2PhMe (bpy = 2,2′-bipyridyl, 5), [Ni(CymCO₂)(bpy)₂(H₂O)][CymCO₂]·0.5MePh·2H₂O (6), [Cu(CymCO₂)₂(imz)₂] (7), and [Cu(CymCO₂)₂(bpy)(H₂O)] (8), were obtained and characterized by single-crystal X-ray analysis. Complexes 1–3 are isostructural. Magnetism of the Co complexes 1, 4, and 5 was studied; it was shown that they exhibit the properties of field-induced single-molecule magnets with magnetization reversal barriers (ΔE/k_B) of 44, 13, and 10 K, respectively. Thermal decomposition of complexes 1–8 was studied by means of DSC and TGA methods. The final products of thermolysis of 1–6 in air, according to powder XRD data, are the pure spinel phases MMn₂O₄; for the cases of copper complexes, the mixtures of CuMn₂O₄ and CuO were found in the products.     

Heavy component of spent nuclear fuel: Efficiency of model-substance ionization by electron-induced discharge

The method of plasma separation of spent nuclear fuel can be tested with a model substance which has to be transformed from the condensed to plasma state. For this purpose, electron-induced discharge in lead vapor injected into the interelectrode gap is simulated using the kinetic approach. The ionization efficiency, the electrostatic-potential distribution, and those of the ion and electron densities in the discharge gap are derived as functions of the discharge-current density and concentration of the vapor of the model substance. Given a discharge-current density of 3.5 A/cm² and a lead-vapor concentration of 2 × 10¹² cm^–3, the simulated ionization efficiency proves to be nearly 60%. The discharge in lead vapor is also investigated experimentally.     

Numerical solution of vector Sturm–Liouville problems with Dirichlet conditions and nonlinear dependence on the spectral parameter

A numerical-analytical iterative method is proposed for solving generalized self-adjoint regular vector Sturm–Liouville problems with Dirichlet boundary conditions. The method is based on eigenvalue (spectral) correction. The matrix coefficients of the equations are assumed to be nonlinear functions of the spectral parameter. For a relatively close initial approximation, the method is shown to have second-order convergence with respect to a small parameter. Test examples are considered, and the model problem of transverse vibrations of a hinged rod with a variable cross section is solved taking into account its rotational inertia.