Vibronic coherence and quantum beats of O2+ based on laser pump-probe dissociation dynamics

Abstract

We report theoretical investigations of vibronic quantum beats (QBs) which can be observed in the molecular dissociation under the intense infrared (IR) laser pump-IR laser probe scheme. We show how the vibronic coherences can be probed by analyzing the interchannel QB signals obtained from the numerical solution of the time-dependent Schr\"odinger equation (TDSE) and the quantum Liouville equation in combination with the strong-field approximation for the treatment of coherences between multiple states of the target ion. The validities of our methods are first tested on a one-dimensional model of ${{\mathrm{H}}_{2}}^{+}$, for which exact solutions of the TDSE can be obtained. We then illustrate our method using an example of ${\mathrm{O}}_{2}$, for which various experiments have been reported recently. The case of an attosecond pump pulse is also considered. Our results indicate that the strong-field dissociation pump-probe experiments are capable of providing information on the vibronic coherences that complements other techniques such as attosecond transient absorption spectroscopy.