Adiabatic theory of ionization of atoms by intense laser pulses: One-dimensional zero-range-potential model

Abstract

As a first step toward the adiabatic theory of ionization of atoms by intense few-cycle laser pulses, here we consider the simplest one-dimensional zero-range-potential model. The theory for this model is developed. This theory rests on a single parameter $\ensuremath{\epsilon}$ giving a ratio of the atomic and laser time scales and becomes exact in the limit $\ensuremath{\epsilon}\ensuremath{\rightarrow}0$ uniformly with respect to the amplitude of the laser pulse. We construct the asymptotics of the solution to the time-dependent Schr\"odinger equation and photoelectron spectrum. The factorization formula for the photoelectron spectrum near its classical boundary, first suggested by T. Morishita et al. [Phys. Rev. Lett. 100, 013903 (2008)] on the basis of ab initio calculations, is derived. The theory is illustrated by numerical calculations. Its comparison with the strong-field approximation is discussed.