Ionization of H ⁺₂ in Intense Laser Fields

Abstract

Recent calculations of ionization rates for H ⁺₂ by an intense λ=228nm laser show a strong dependence of the rate constant on the internuclear distance R. We have performed comparable time-dependent calculations for H ⁺₂ in fields I≤1×10 ¹⁵W/cm² for a wide range of fixed R (2–8au) and wavelengths (228–1064 nm). Indeed we obtain excellent agreement with the results of Chelkowski etal ¹ at λ=228nm. At large R we find the ionization rate for all wavelengths rapidly approaches that of H(ls). However, at R≈2au and especially for the longer wavelength lasers, such as the λ=769nm Ti: sapphire laser, the large ionization potential (29eV) of the molecule allows it to easily survive intensities up to I=5×10 ¹⁴W/cm² for typical short pulses of, say, 150 fsec.