Measurement of hydrogenic tunneling rates in a high-intensity laser focus

Abstract

An accurate measurement of the tunneling ionization rate for the hydrogenic ground state of helium $({\text{He}}^{1+})$ in a circularly polarized, $2\text{\ensuremath{-}}\text{ps}$, high-intensity laser pulse is presented. The ionizing electric fields are determined with an uncertainty of less than $2%$ by measuring the energies of electrons ponderomotively accelerated out of the focus. The inferred ionization rate agrees well with semiclassical and exact solutions of the Schr\odinger equation.