Thermalization of coupled atom-light states in the presence of optical collisions

The interaction of a two-level atomic ensemble with a quantized single mode electromagnetic field in the presence of optical collisions (OC) is investigated both theoretically and experimentally. The main accent is made on achieving thermal equilibrium for coupled atom-light states (in particular dressed states). We propose a model of atomic dressed state thermalization that accounts for the evolution of the pseudo-spin Bloch vector components and characterize the essential role of the spontaneous emission rate in the thermalization process. Our model shows that the time of thermalization of the coupled atom-light states strictly depends on the ratio of the detuning and the resonant Rabi frequency. The predicted time of thermalization is in the nanosecond domain and about ten times shorter than the natural lifetime at full optical power in our experiment. Experimentally we are investigating the interaction of the optical field with rubidium atoms in an ultra-high pressure buffer gas cell under the condition of large atom-field detuning comparable to the thermal energy in frequency units. In particular, an observed detuning dependence of the saturated lineshape is interpreted as evidence for thermal equilibrium of coupled atom-light states. A significant modification of sideband intensity weights is predicted and obtained in this case as well.Comment: 14 pages, 12 figures; the content was edite

Laser assisted charge transfer reactions in slow ion–atom collisions: Coupled dressed quasimolecular‐states approach

This is the published version, also available here: http://dx.doi.org/10.1063/1.447712.Semiclassical coupled dressed quasimolecular states (DQMS) approaches are presented for the nonperturbative treatment of charge transferreactions at low collision velocities and high laser intensities. The DQMS are first obtained via the Floquet theory. The laser assisted collision process can then be treated as the electronic transitions among the DQMS driven by the nuclear motion only. The expansion of the total electronic wave function in a truncated DQMS basis results in a set of coupled a d i a b a t i c equations. The adiabatic DQMS and their associated quasienergies (depending parametrically upon the internuclear separation R) exhibit regions of avoided crossings, where the electronic transition probabilities are large due to strong radial couplings induced by the nuclear movement. By further transforming the a d i a b a t i c DQMS into an appropriate d i a b a t i c DQMS representation, defined via the vanishing of the aforementioned radial couplings, we obtain a new set of coupled d i a b a t i c equations which offer computational advantage. The method is illustrated by a case study of the laser assisted charge exchange process He+ ++H(1s)+ℏω→He+(n=2)+H+, in a two‐state approximation, for the velocity range from 1.5×105 to 2×107 cm/s and for the laser intensity in the range of 0.4 to 4.0 TW/cm2. Results of exact coupled diabatic DQMS calculations are presented along with several approximation calculations, using first order perturbation theory, the Magnus approximation, and the average cross section

The influence of coordinative tartrate and malatogermanate compounds on the activity of α-L-rhamnosidase preparations from Penicillium tardum, Eupenicillium erubescens and Cryptococcus albidus

Recently enzyme preparations of microbial origin become increasingly important in different industries. Preparations of α-L-rhamnosidase are used in the pharmaceutical industry as well as in scientific work as a tool for analytical research. We have obtained purified α-L-rhamnosidase preparations from Penicillium tardum, Eupenicillium erubescens and Cryptococcus albidus microorganism strains which are effective enzyme producers. The aim of the study was to estimate the ability of germanium coordination compounds to enhance enzyme catalytic activity. The effects of 11 heterometal mixed ligand tartrate (malate-)germanate compounds at 0.01 and 0.1% concentration on the activity of α-L-rhamnosidase preparations from Penicillium tardum IMV F-100074, Eupenicillium erubescens and Cryptococcus albidus 1001 were studied at 0.5 and 24 h exposition. The inhibitory effect of [Ni(bipy)3]4[{Ge2(OH)2(Tart)2}3Cl2]·15H2 on P. tardum α-L-rhamnosidase was revealed. All studied compounds except [CuCl(phen)2][Ge(OH)(HMal)2] were shown to increase activity of P. tardum α-L-rhamnosidase at a longer term of exposition. Activity of E. erubescens α-L-rhamnosidase was shown to be stimulated by d-metal cation-free compounds. C. albidus α-L-rhamnosidase occurred to be insensitive to all compounds studied