Wavelength Dependence of Atomic Excitation for Ar Subject to Intense Midinfrared Laser Pulses

Abstract

Experimental and theoretical investigations of the wavelength dependence of the Rydberg states excitation (RSE) process of Ar atom subject to intense laser fields are reported. By simultaneously measuring ionization and Rydberg-state excitation yields of an argon atom subject to a strong laser field for various wavelengths, we demonstrate that the wavelength scaling law of the ratio of Ar* over Ar+ with respect to the laser intensity, and this result can be well reproduced by a nonadiabatic model, but not by the classical-trajectory Monte Carlo (CTMC) model. Our results indicate that, the nonadiabatic corrections of the photoelectron tunneling exit and tunneling probability play a significant role at shorter wavelengths. Analysis shows that the wavelength dependence phenomenon is due to the interplay of the nonadiabatic effect, wave-packet diffusion and Coulomb focusing effect of the liberated electron.