Loschmidt echo and stochastic-like quantum dynamics of nano-particles

We investigate time evolution of prepared vibrational state (system) coupled to a reservoir with dense spectrum of its vibrational states. We assume that the reservoir has an equidistant spectrum, and the system - reservoir coupling matrix elements are independent of the reservoir states. The analytical solution manifests three regimes of the evolution for the system: (I) weakly damped oscillations; (II) multicomponent Loschmidt echo in recurrence cycles; (III) overlapping recurrence cycles. We find the characteristic critical values of the system - reservoir coupling constant for the transitions between these regimes. Stochastic dynamics occurs in the regime (III) due to inevoidably in any real system coarse graining of time or energy measurements, or initial condition uncertainty. Even though a specific toy model is investigated here, when properly interpreted it yields quite reasonable description for a variety of physically relevant phenomena.Comment: 8 pages, 3 figure

Quantum Dynamical Rate Constant for the H + O3 Reaction Using a Six-Dimensional Double Many-Body Expansion Potential Energy Surface

We present a quantum mechanical, three-dimensional, infinite-orden-sudden-approximation study of the H + O3 atmospheric reaction using a recently reported double many-body expansion potential energy surface for ground-state HO3. The results are compared with existing experimental data and previously reported quasiclassical trajectory calculations which employed the same interaction potential. Agreement with the recommended experimental data is moderate, but encouraging when compared with the data of Clyne and Monkhouse, which extends over the range of temperatures 300 ≤ T/K ≤ 650, and with the recent measurement of Greenblatt and Wiesenfeld for T = 300 K. In comparison with the classical trajectory results, the agreement is also moderate, the differences being attributed to both methodological approximations in the quantum formalism and the problem of zero-point energy leakage in classical dynamics