Spin-orbit effects in electron transfer in neptunyl(VI)-neptunyl(V) complexes in solution

The spin-orbit effects were investigated on the complexes involved in the electron self-exchange between Np(V) and Np(VI) in both the outer-sphere and inner-sphere mechanisms, the latter for binuclear complexes containing hydroxide, fluoride, and carbonate as bridging ligands. Results obtained with the variation-perturbation and the multireference single excitation spin-orbit CI calculations are compared. Both effects due to different relaxations of spinors within a multiplet (spin-orbit relaxation) and scalar (electrostatic) relaxation effects in the excited states are accounted for in the latter scheme. The results show that the scalar (electrostatic) relaxation is well described by the single-excitation spin-orbit CI, and that spin-orbit relaxation effects are small in the Np complexes, as in the lighter d-transition elements but in contrast to the main group elements.     

Synthesis of lithium-manganese oxide spinel in hydrothermal conditions

Abstract

Lithium-manganese oxide spinel LiMn₂O₄ was synthesized in hydrothermal conditions (400°C, 20 MPa) in the course of thermovaporous treatment mixtures of MnO₂ and LiOH/or Li₂CO₃. The conditions of synthesis of the spinel as monophase product were determined. The obtained product has been characterized by means of various physical and chemical methods. The spinel has been used for manufacturing cathodes of rechargeable lithium cells. The cells discharged in the potential range 2.8-3.5 V. The specific capacity was 100-140mAh/g.     

Ab Initio Molecular Dynamics Study of Hydrogen Cleavage by a Lewis Base [tBu3P] and a Lewis Acid [B(C6F5)3] at the Mesoscopic Level—Dynamics in the Solute–Solvent Molecular Clusters

With the help of state‐of‐the‐art ab initio molecular dynamics methods, we investigated the reaction pathway of the {tBu₃P + H₂ + B(C₆F₅)₃} system at the mesoscopic level. It is shown that: i) the onset of H₂ activation is at much larger boron???phosphorus distances than previously thought; ii) the system evolves to the product in a roaming‐like fashion because of quasi‐periodic nuclear motion along the asymmetric normal mode of P???H?H???B fragment; iii) transient configurations of a certain type are present despite structural interference from the solvent; iv) transient‐state configurations with sub‐picosecond lifetime have potentially interesting infrared activity in the organic solvent (toluene) as well as in the gas phase. The presented results should be helpful for future experimental and theoretical studies of frustrated Lewis pair (FLP) activity.     

Application of lasers in precision analytical measurements (review)

Conclusions The foregoing analysis does not exhaust the analytic methods of laser spectroscopy (see, e.g., [6–8, 142, 143]). The methods of traditional [8–10, 144, 145] resonance [8, 146], and active (or CARS) [8, 11, 147] Raman scattering spectroscopy are continuously being expanded. Newer, purely laser methods — optogalvanic spectroscopy [25, 148], optothermal spectroscopy [7, 149], the method of selective photoionization [6, 150], etc. — are also being developed.Further development of laser spectra analysis will primarily require going beyond narrow laboratory, purely research setups, and the development of commercial laser analytic devices. In this connection, in selecting a method as the basis for the device being constructed it is necessary to know not only the technical characteristics, such as sensitivity, selectivity, speed of operation, etc., but also the metrological characteristics, such as the random and systematic measurement errors; in addition, the measurement accuracy is a decisive factor. At the same time there are few works devoted to the questions of accuracy of the measurements performed with laser spectrometers; in the literature available to us there are no reviews and comparisons of analytic methods of laser spectroscopy from this viewpoint.Amongst the foregoing methods the direct absorption method has the highest accuracy. With a definite arrangement of the measurement process this method enables absolute measurements of the concentration of the analyte component, i.e., it does not require precalibration of the apparatus based on gas mixtures (for the gas analyzer). The minimum achievable error of such measurements is limited by the error of the premeasured absorption coefficient for radiation of the molecule being detected at the wavelength of the laser radiation and at the present time can equal 1–3%. Other methods studied are characterized by higher sensitivity, and they are also more accurate, difficult to calibrate, and less versatile. A comparative analysis of the methods and their errors will be performed in the future.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 48, No. 1, pp. 7–26, January, 1988.We thank A. P. Voitovich for useful remarks and a discussion of this work.     

Description of the inner state and kinetics of Rydberg atoms based on the kinetic Boltzmann equation for Rydberg electrons

The inner characteristics and kinetics of Rydberg atoms (RAs) excited selectively over energy in a buffer gas are considered using the kinetic equation for a classical distribution function of Rydberg electrons (REs). The distribution of REs over coordinates and velocities in a moving RA is found in the general case. In a moving RA, the effect of “ blowing off” an electron cloud by a buffer gas is substantial. In this case, however, the average values of the kinetic and potential energies of REs weakly deviate from those predicted by the virial theorem. The latent and macroscopic polarizations of the medium caused by the blowing-off effect are predicted. The macroscopic polarization appears upon velocity-selective excitation of RAs and produces the bias current, which transforms to a usual electric current when the integrity of the RA is lost due to the blowing-off effect. The calculated “ electron” contribution to the transport frequency of collisions of the RA with buffer gas atoms proved to be small compared to that from the ion core.     

Quadrupole relaxation enhancement--application to molecular crystals

A general theory of field dependent spin-lattice relaxation for nuclei of the spin quantum number 1/2 (1H, 19F, 13C) caused by dipole-dipole interactions with neighboring quadrupolar nuclei (nuclei possessing a quadrupolar moment) is presented. The theory is valid for arbitrary motional conditions and should be treated as a quadrupolar counterpart of the paramagnetic relaxation enhancement theory. When the energy level splitting of the dipolar spin (I=1/2) matches one of the transition frequencies of the quadrupolar nuclei one can observe a local enhancement of the dipolar spin relaxation (referred to as "quadrupolar peaks"). To see such effects the dynamics modulating the spin interactions has to be relatively slow. This brings the system beyond the validity range of perturbation approaches and requires the stochastic Liouville equation to be applied. The presented theory describes the quadrupolar relaxation enhancement (QRE) for an arbitrary spin quantum number of the quadrupolar nuclei and includes the asymmetry of the quadrupolar coupling. It has been applied to interpret the shape of magnetization curves (amplitude of 1H magnetization versus magnetic field) for the molecular crystal [C3N2H5]6[Bi4Br18] ([C3N2H5]-imidazolium). The magnetization curves show several dips (local minima) attributed to 1H-14N quadrupolar relaxation enhancement effects. In addition, as a limiting case a perturbation approach to QRE has been presented and its validity conditions have been discussed.     

The Sounding of Hydrogen Sulfide Molecules by the Raman Light Scattering Lidar Installed on a Flying Platform

Optics and Spectroscopy - The lidar equation is solved numerically for the Raman backscattering by hydrogen sulfide molecules in the atmosphere and water with concentrations about 1011–1015...