Vibrational ladder climbing dissociation of LiH molecules excited by non-chirped pulses

Abstract

Vibrational ladder climbing (VLC) is one of the advanced methods for achieving molecular dissociation, usually requires the use of chirped laser pulses to adapt to the change of energy difference between molecular vibrational levels. In this work, a scheme is proposed for using non-chirped pulses to couple the vibrational rotational levels of excited state to realize VLC dissociation of LiH molecules in the excited state. The first pulse induces population excitation to the excited state A¹Σ⁺, while the second pulse is used to drive the excited state vibrational levels population up step by step until dissociation occurs. The non-chirped pulse VLC dissociation dynamics is investigated using the time-dependent quantum wave packet theory method. The ""climb steps" process for excited state molecules at low full width at half maximum (FWHM) of the second laser pulse is demonstrated. The frequency has an obvious influence on the distribution of excited state vibrational rotational levels and further affects the relaxation process of the undissociated part and the angular distribution of dissociation products. It is also explained that the anomalous decrease of dissociation probability is caused by vibrational levels oscillation.

Keywords: Photodissociation; Time-dependent wave packet method; Vibrational ladder climbing.