STATE-SELECTIVE VIBRATIONAL-EXCITATION OF DIATOMIC-MOLECULES COUPLED TO A QUASI-RESONANT ENVIRONMENT - MARKOV APPROXIMATION AND NON-MARKOV APPROACH

Laser-controlled ultrafast state-selective vibrational dynamics of dia tomic molecules, which are coupled to an unobserved quasiresonant envi ronment is investigated using the reduced density-matrix formalism bey ond and within a Markov-type approximation. Dissipative quantum dynami cs in a classical electric field of shaped infrared ultrashort laser p ulses is simulated for a one-dimensional nondissociative Morse oscilla tor, representing the local OH bond in the H2O and HOD molecules in th e electronic ground state. Localization of population at a prescribed vibrational target level of OH up to v = 10 with probability of about 90% is demonstrated on a picosecond time scale, while the strength of the quasiresonant molecule-environment coupling results in subpicoseco nd lifetimes of the vibrational states. The laser-controlled stabiliza tion of selective excitation in the restricted set of vibrational stat es against a background of strongly diminished relaxation to lower vib rational states is also shown. The laser-control scheme may include a superposition of several laser pulses. A Markov-type approximation res ults in slightly increased lifetimes of the vibrational states, along with decreased predicted probability of state-selective excitation of a molecule by about 20-30 %. Several results obtained within the fourt h-order perturbation theory in interaction of a molecule with an envir onment are in a good agreement with the non-Markov analysis.