Accession Number : ADA116253

Title :   Quantum Dynamical Model of Laser-Stimulated Isotope Separation of Adsorbed Species: Role of Anharmonicity, Coupling Strength and Energy Feedback from the Heated Substrate.

Descriptive Note : Technical rept.,


Personal Author(s) : Lin,Jui-Teng ; George,Thomas F

PDF Url : ADA116253

Report Date : Jun 1982

Pagination or Media Count : 63

Abstract : A quantum model of a heterogeneous system consisting of a mixture of isotopes adsorbed on a solid surface and subjected to laser radiation is presented. The model system is described by a total Hamiltonian including direct and indirect (surface-phonon-mediated) couplings. The equations of motion are derived in the Heisenberg-Markoffian picture in which the many-body effects of the surface phonon modes and the ad-species are reduced to an overall broadening (damping factor) given by the sum of the energy (T1) and phase (T2) relaxations. The effects of the dephasing and anharmonicity on the average excitation are investigated. The 'bistability' feature with a red-shifted optimal detuning is discussed in terms of the solution of a cubic equation. A diagonalization procedure is presented in a new basis which reveals the effects of the coupling strength, the frequency difference and the level width of the isotopes on the total steady-state excitation, which in turn reflects the surface spectrum of the model system. Finally, the isotope selectivity given by the numerical results of the time-integrated excitations is discussed. It is shown that the optimal detuning for a weak coupling strength is further red-shifted for a strong isotopic coupling strength. Finally, energy feedback effects of the bath modes on the excitations of the active modes are investigated by combining a quantum excitation equation and a classical heat diffusion equation. (Author)

Descriptors :   *Isotope separation, *Radiation absorption, *Laser beams, *Quantum theory, *Coupling(Interaction), Energy transfer, Dynamics, Strength(General), Thermal diffusion, Excitation, Relaxation, Steady state, Heterogeneity, Substrates, Damping, Equations of motion, Mathematical models, Time dependence, Heat treatment, Feedback

Subject Categories : Quantum Theory and Relativity

Distribution Statement : APPROVED FOR PUBLIC RELEASE