Tunneling photodetachment of negative ions exposed to a bichromatic laser field

Abstract

Tunneling photoionization by a bichromatic field consisting of the coherent superposition of the fundamental laser field frequency and its second harmonic is studied theoretically within the framework of the adiabatic Landau–Dykhne approach applied to the process of negative-ion photodetachment. Analytical expressions for the probability of photodetachment were derived at two fixed specified values of relative phase shift, Φ=0 and Φ=π/2, between the harmonics of the incident bichromatic field. The derived expressions are thoroughly analyzed for two possible limiting cases of tunneling and multiphoton ionization and are demonstrated to be different from the respective expressions for the monochromatic case because of the presence of an effective field strength, which is a function that strongly depends on the parameters of the incident bichromatic field.