Ultrafast laser-pulse control for selective excitation of high vibrational states and dissociation of diatomic molecules in an environment

Abstract

Ultrafast state-selective vibrational excitation and dissociation controlled by shaped subpicosecond infrared laser pulses is investigated within the reduced density matrix formalism beyond a Markov-type approximation for diatomic molecules, which are coupled to an unobserved quasiresonant environment. Dissipative quantum dynamics in a classical electric field is simulated for discrete vibrational bound states and for dissociative continuum states of a one-dimensional dissociative Morse oscillator, tailored to the local OH bond of the H2O and HOD molecules in the electronic ground state. Flexible laser control schemes are developed and demonstrated on a picosecond time scale, which enable one either to localize the population at prescribed high-lying discrete vibrational levels of OH, up to those close to the dissociation threshold, with the probability up to 70–80 % without substantial dissociation or, alternatively, achieve the dissociation yield of about 75%, while the strength of the quasiresonant molecule-environment coupling results in subpicosecond lifetimes of the vibrational bound states. The optimal laser control schemes may include the superposition of up to four subpicosecond laser pulses. @S1050-2947~97!02710-8#