Nonlinear Ionization of Molecules by Intense Transform-Limited Gaussian Laser Pulses

We present in this paper an investigation of the nonlinear process of above-threshold ionization. The process arises when an atomic or molecular system, exposed to an intense laser pulse, conti-nues to absorb more photons than that needed for the ionization to occur. We trigger this non-linear process in a simple molecular system by exposing it to an intense transform-limited Gaus-sian laser pulse of 267-nm wavelength which is the third harmonic of an 800-nm wavelength Ti-sapphire laser. We explore the characteristics of the process by analyzing the kinetic-energy spec-tra of the electrons ejected from the molecular system under different laser peak intensities