Dynamics of the two-atom Jaynes-Cummings model with nondegenerate two-photon transitions

An exact solution is found for the collective model of two identical two-level atoms that resonantly interact with a two-mode quantum electromagnetic field in an ideal cavity via two-photon nondegenerate transitions. In the case under study, at the initial moment, both field modes are in the coherent state and atoms are in the excited state. The time dependences of the atomic probabilities, the mean number of photons in the modes, and the statistics and squeezing of the photon modes are studied based on the exact solution.     

Quantum-interference effects for gamma radiation under crossing-anticrossing conditions for nuclear levels in an RF field

A new approach to observing the effect of electromagnetically induced transparency in gamma optics is proposed. The propagation of a resonant photon in a ⁵⁷Fe magnetic medium in an applied rf field is considered for this purpose. It is shown that, under crossing-anticrossing conditions, a resonant rf field substantially changes the gamma-optical properties of the medium, which become dependent on the parameters of the field. This opens the possibility for exercising a coherent control of the photon group velocity and a controllable filtration of unpolarized gamma radiation in a sample.     

Collective radiation of a system of two three-level V-type atoms in a two-mode resonator with losses

Collective spontaneous radiation of a system of two three-level V-type atoms interacting with two modes of a quantum electromagnetic field in a resonator with finite Q-factor is investigated based on the control kinetic equation for the density matrix. Time dependences of the average number of photons and radiation intensity of each mode are derived for the case in which atoms at the initial moment of time are in different excited states. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 78–83, February, 2006.     

Disproportionation of olefins on aluminum-molybdenum and aluminum-rhenium catalysts,promoted by tin tetraalkyl derivatives

Conclusions The treatment of Al-Re catalysts with tetraalkylstannanes substantially increases their activity in the disproportionation reactions of olefins and trimethylvinylsilane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 678–679, March, 1977.     

Transport phenomena in a plane shock wave

With the use of the nonpolynomial closure 1/ _z in the Mott-Smith approximation of the solution of the Boltzmann equation, we obtain a value of the density gradient in the limit of a very weak shock wave that is close to the correct value. For the determination of the transverse temperature gradient we calculated the _x ² / _z moment of the Mott-Smith collision integral. The effective values of viscosity and thermal conductivity in the limit of a very weak shock wave were calculated for inverse-power potentials and found to agree almost exactly with the Chapman-Enskog values. Such a comparison can serve as a criterion for the evaluation of different bimodal theories. Various bimodal theories give different values of viscosity and thermal conductivity, but all of them give 33 % too high a value of the Eucken ratio.     

A Unified Mechanism on the Formation of Acenes,Helicenes, and Phenacenes in the Gas Phase

A unified low‐temperature reaction mechanism on the formation of acenes, phenacenes, and helicenes—polycyclic aromatic hydrocarbons (PAHs) that are distinct via the linear, zigzag, and ortho‐condensed arrangements of fused benzene rings—is revealed. This mechanism is mediated through a barrierless, vinylacetylene mediated gas‐phase chemistry utilizing tetracene, [4]phenacene, and [4]helicene as benchmarks contesting established ideas that molecular mass growth processes to PAHs transpire at elevated temperatures. This mechanism opens up an isomer‐selective route to aromatic structures involving submerged reaction barriers, resonantly stabilized free‐radical intermediates, and systematic ring annulation potentially yielding molecular wires along with racemic mixtures of helicenes in deep space. Connecting helicene templates to the Origins of Life ultimately changes our hypothesis on interstellar carbon chemistry.