Non-Markovian dynamics of an open quantum system with nonstationary coupling.

The spectral, dissipative, and statistical properties of the damped quantum oscillator are studied in the case of non-Markovian and nonstationary system-heat bath coupling. The dissipation of collective energy is shown to be slowed down, and the decoherence rate and entropy grow with modulation frequency.

Non-Markovian dynamics of quantum systems. II. Decay rate, capture, and pure states.

On the basis of a master equation for the reduced density matrix of open quantum systems, we study the influence of time-dependent friction and diffusion coefficients on the decay rate from a potential well and the capture probability into a potential well. Taking into account the mixed diffusion coefficient Dqp, the quasistationary decay rates are compared with the analytically derived Kramers-type formulas for different temperatures and frictions. The diffusion coefficients supplying the purity of states are derived for a non-Markovian dynamics.

Non-Markovian dynamics of quantum systems. I. Formalism and transport coefficients.

Generalized Langevin equations and fluctuation-dissipation relations are derived for the case of a nonlinear non-Markovian noise. The explicit expressions for the time-dependent friction and diffusion coefficients are presented for the case of general and linear couplings in the coordinate and momentum between the collective harmonic oscillator and heat bath. The long-time tails of correlation functions are investigated in the low- and high-temperature regimes of dissipation for different couplings. The Onsager's regression hypothesis is discussed for the non-Markovian dynamics. The Lindblad theory is justified on the basis of the microscopical model.

Precise determination of the 2s(1/2)-2p(1/2) splitting in very heavy lithiumlike ions utilizing dielectronic recombination.

The 2s(1/2)-2p(1/2) energy splittings DeltaE(L) of the lithiumlike ions 19779Au76+, 20882Pb79+, and 23892U89+ have been measured at the Experimental Storage Ring, utilizing low energy dielectronic recombination. The resonance energies in total 41 different 1s(2) 2p(1/2)nl(j(')) (n > or =20) autoionizing Rydberg states populated in the dielectronic capture process have been determined. The 2s(1/2)-->2p(1/2) excitation energies have been obtained by extrapolation of these resonance energies to the associated series limits n--> infinity. The combined analysis of the experimental data for all three ions yields DeltaE(L)=216.134(96) eV for Au76+, 230.650(81) eV for Pb79+, and 280.516(99) eV for U89+.

High Rydberg resonances in dielectronic recombination of pb(79+).

Dielectronic recombination resonances of Pb (79+) associated with 2s(1/2)-->2p(1/2) excitations were measured at the heavy-ion storage ring ESR at GSI. The fine structure of the energetically lowest resonance manifold Pb (78+)(1s(2)2p(1/2)20l(j)) at around 18 eV could partially be resolved, and rate coefficients on an absolute scale were obtained. A comparison of the experimental data with results of a fully relativistic theoretical approach shows that high-angular-momentum components up to j=31/2 significantly contribute to the total resonance strength demonstrating the necessity to revise the widespread notion of negligible high-angular-momentum contributions at least for very highly charged ions.

Comment on "Vacuum electron acceleration by coherent dipole radiation".

Troha et al. [Phys. Rev. E 60, 926 (1999)] put forward a generalized Lawson-Woodward theorem in the study of laser accelerations. We point out that one of the assumptions used in their proof does not stand on a solid physical ground and that it is possible for electrons to obtain net energy gains from a plane-wave laser pulse in vacuum even if the radiation reaction effects are neglected.

Fifth-order corrected field descriptions of the Hermite-Gaussian (0,0) and (0,1) mode laser beam.

In this paper, we extend the work of Barton and Alexander [J. App. Phys. 66, 2800 (1989)] on the fifth-order corrected field expressions for a Hermite-Gaussian (0,0) mode laser beam to more general cases with adjustable parameters. The parametric dependence of the electron dynamics is investigated by numerical methods. Finally, the fifth-order corrected field equations for the Hermite-Gaussian (0,1) mode are also presented.

Purity and decoherence in the theory of a damped harmonic oscillator.

For the generalized master equations derived by Karrlein and Grabert for the microscopic model of a damped harmonic oscillator, the conditions for purity of states are written, in particular for different initial conditions and different types of damping, including Ohmic, Drude, and weak coupling cases, and the Agarwal and Weidlich-Haake models. It is shown that the states which remain pure are the squeezed states with variances that are constant in time. For pure states, generalized nonlinear Schrödinger-type equations corresponding to these master equations are also obtained. Then the condition for purity of states of a damped harmonic oscillator is considered in the framework of Lindblad theory for open quantum systems. For a special choice of the environment coefficients, correlated coherent states with constant variances and covariance are shown to be the only states which remain pure all the time during the evolution of the considered system. In Karrlein-Grabert and Lindblad models, as well as in the particular models considered, expressions for the rate of entropy production are written, and it is shown that state which preserve their purity in time are also states which minimize entropy production and, therefore, are the most stable state under evolution in the presence of the environment, and play an important role in the description of decoherence phenomenon.

High-intensity laser-induced electron acceleration in vacuum.

In this paper, an approximate pulsed-laser-beam solution of Maxwell's equation in vacuum is derived. Then with the numerical simulation method, electron acceleration induced by high-intensity [Q(0)=eE(0)/(m(e)omega c)=3] lasers is discussed in connection with the recent experiment of Malka et al. It is found that the maximum energy gain and the relationship between the final energy and the scattering angle can be well reproduced, but the polarization effect of electron-laser interactions is not very prominent. These results show that the ponderomotive potential model is still applicable, which means that the stimulated Compton scattering is the main fundamental mechanism responsible for the electron acceleration at this laser intensity.

Fluence and mutagenic side effects of excimer laser radiation applied in ophthalmology in human lymphocytes in vitro.

PURPOSE: To investigate the influence of different fluences in 193 and 248 nm excimer laser radiation on the yields of chromatid and chromosome aberrations induced in human lymphocytes in vitro. METHOD: Heparinized human blood was exposed to 193 or 248 nm excimer laser radiation. The fluence was gradually increased from 21 to 400 mJ/cm2 in 193 nm (constant total energy of 250 J) and from 150 to 377 mJ/cm2 in 248 nm radiation (constant total energy of 500 J). Chromatid and chromosome aberrations were then analysed microscopically. RESULTS: The yields of chromatid breaks and achromatic lesions depend on the fluence per pulse. This dependence contains a linear component, indicating a threshold of about 70 mJ/cm2 fluence in 193 nm and of about 250 mJ/cm2 fluence in 248 nm laser radiation. An increase of the yield of dicentric chromosomes could only be observed at the highest fluence tested (377 mJ/cm2) in the 248 nm series. Over 126 mJ/cm2 in 193 nm radiation no lymphocytes could be cultured and therefore no aberrations could be found. CONCLUSIONS: Our findings show that the fluence of 193 nm and of 248 nm excimer laser radiation has an effect on the yields of chromatid breaks and achromatic lesions in human lymphocytes under in vitro conditions.

Biological dosimetry after extensive diagnostic x-ray exposure.

The yield of chromosome aberrations (dicentric and ring chromosomes) was determined for five patients who had been extensively exposed to diagnostic x rays. Remarkably high aberration yields were obtained for each of them leading to correspondingly high equivalent whole body doses ("biological dosimetry"). The contribution of iodized contrast media and computing tomography to the biologically estimated doses is discussed.