CIDNP of 13C and 1H nuclei in the reactions of cyclohexadienone carbenes

Thermal decomposition of 4-diazo-2,6-di-tert-butyl-2, 5-cyclohexadien-1-one in perhalogenated solvents has been investigated. The decomposition reaction proceeds via a carbene intermediate first to a singlet and then to an effectively triplet free encounter radical pair formed in a halogen abstraction reaction. The polarisation of the stable reaction product is determined by competing processes in the primary cage, intersystem crossing and escape from the cage.     

The physical kinetics of magnetoplasticity of diamagnetic crystals

The kinetic equations describing the rate of magnetically induced release of dislocations entrapped by stoppers were solved. The magnetic field effect on the mobility of dislocations was calculated. Its comparison with experiment gave the ratio between the rate constants for two key processes governing magnetoplasticity, namely, singlet-triplet conversion in a spin nanoreactor and the release of a dislocation from it. The kinetic criterion of the existence of magnetoplasticity as a physical phenomenon was obtained.     

The dynamics of nonadiabatic transitions in collisions between the I<Subscript>2</Subscript>(<Emphasis Type="Italic">E</Emphasis>) and I<Subscript>2</Subscript>(<Emphasis Type="Italic">X</Emphasis>) molecules

The paper presents the results of a theoretical study of the dynamics of nonadiabatic transitions between the ion-pair states E0 _g ⁺ and D0 _u ⁺ of the I₂ molecule induced by collisions with the I₂ molecule in the ground electronic state X0 _g ⁺ . The potential energy surfaces and diabatic coupling matrix elements of electronic states were obtained using a model based on the diatomics-in-molecule approximation. Special perturbation theory for intermolecular interaction was used to show that the large transition dipole moment between the E0 _g ⁺ and D0 _u ⁺ states caused the appearance of additional long-range corrections, an electrostatic dipole-quadrupole correction to the diabatic coupling matrix elements and induction dipole-dipole correction to the potential energy surface. The influence of these corrections on nonadiabatic dynamics was studied at the level of the semiclassical approximation. The electrostatic correction was found to sharply increase the contribution of resonance (accompanied by minimum kinetic energy changes) vibronic transitions at large distances between the colliding molecules. The induction correction had the opposite effect because of the high transition probability at short distances. The results obtained were in qualitative agreement with experimental data. The conclusion was drawn that obtaining quantitative agreement required a more balanced inclusion of interactions at short and long distances.