Controlled Vibrational Quenching of Nuclear Wave Packets in D

Ionization of neutral D2 molecules by a short and intense pump laser pulse may create a vibrational wave packet on the lowest (1sσ+ g ) adiabatic potential curve of the D 2 molecular ion. We investigate the possibility of manipulating the bound motion, dissociation, and vibrational– state composition of such nuclear wave packets with ultra–short (6 fs) intense (1× 1014 W/cm2) near infrared (800 nm) control laser pulses [1]. The influence of such control pulses has been shown to lead to vibrational cooling and to modify dissociation yields [2]. We show numerically that a single control pulse with an appropriate time delay can quench the vibrational state distribution of the nuclear wave packet by increasing the contribution of a selected stationary vibrational state of D 2 to more than 50%. We also demonstrate that a second control pulse with a carefully adjusted delay can further squeeze the vibrational state distribution, thereby suggesting a multi–pulse control protocol for generating almost stationary excited nuclear wave functions. The quality of this Raman–control mechanism can be tested experimentally by fragmenting the molecular ion with an intense probe pulse and by identifying the nodal structure of the surviving vibrational state in the kinetic energy release spectrum of the molecular fragments [3, 4]. The probability Pν(t) for finding the system at time t > 0 in the ν–th vibrational state is the quantum mechanical overlap of the calculated bound wave function χg(t) with the known eigenfunctions χν of the 1sσ+ g curve, Pν(t) = |〈χν |χg(t)〉| 〈χg(t)|χg(t)〉 .