Simulation of pump-probe spectroscopy of a highly-charged diatomic molecule: Role of intermediate charged states and electronic and vibrational excitation in the multiple ionization of Cl_2 and strong-field spectroscopy of Cl_2~(3+)

摘要

This paper is a theoretical study of the effect of a pusled ir laser on a neutral Cl_2 molecule, leading to the creaction by highly-charged molecular ions. We also develop a new quantum-mechanical model for the ionization of diatomic molecules in the tunneling regime. We consider the effects of the pump pulse duration and also the wavelength of the probe laser on the trication Cl_2~(3+) which is metastable, and consider how an experiment could be performed which would lead to the observation of its vibrational spectrum. The treatment considers nuclear wave packet dynamics which begin with vertical ionization from neutral Cl_2 to Cl_2~(2+), includes dynamics arising from the intermediate charged state Cl_2~(2+), and electronic excitation and dissociation from the trication Cl_2~(3+). The dynamical simulations of a pump-probe experiment show modulated signals which can be Fourier-transformed to yield vibrational spectra. The quality of the modulated signal changes dramatically at an intermediate (relative to the vibrational period) pump pulse duration (at ca. 50 fs). Analysis of this effect shows how to maximize the probability of observing a simple vibrational spectrum for a highly charged diatomic created in a laser field.