Total ionization rates and ion yields of atoms at nonperturbative laser intensities

Abstract

We investigate a simply corrected Keldysh-Faisal-Reiss ͑KFR͒ rate formula for laser-induced ionization of atoms in the nonperturbative intensity domain. Predictions of the formula are compared, first, with ab initio Floquet calculations, which show good agreement in the nonperturbative intensity domain for not too short wavelengths. Second, they are found to agree with the results of numerical simulations for the H atom, provided the pulse lengths are not shorter than three field cycles, so that the adiabatic rate becomes a valid parameter. Finally, total single-ionization yields predicted by the present model are compared with 36 different experimental data sets for He, Ne, Ar, Kr, and Xe, covering both linear and circular polarizations, and different wavelengths, pulse durations, and intensities; the results show a remarkable overall agreement with the data.

Multiphoton ionization and multiphoton resonances in the tunneling regime

“…The agreement shows that the choice of gauge is not critical in this problem and confirms the validity of the Coulomb correction proposed in Ref. [21]. In contrast to the SFA, the ω 2 expansion yields rates varying smoothly at thresholds.…”

“…We also present results obtained within Faisal's and Reiss's velocity-gauge formulation of the SFA [19,20], corrected for the Coulomb interaction between the photoelectron and the ionic core as proposed by Becker et al [21]. In the single-active-electron approximation, the corresponding Coulomb-corrected Faisal-Reiss rate for ionization from an S state by the linearly polarized field (2) is [30] …”

“…The Coulomb correction is effected by the factor C 2 : C 2 = 1 for detachment from a short-range potential while C 2 = (κ 3 /F 0 ) 2n * for ionization of an atom [21]. We evaluate the quantity χ (k n )|φ i by Fourier transforming the wave function of the field-free initial state calculated using the model potentials and the basis set method described in Sec.…”

“…The velocity-gauge formulation is that developed by Faisal [19] and by Reiss [20], and it treats the time integral exactly (this integral is reduced to a generalized Bessel function which can be calculated accurately). We use the correction proposed by Becker et al [21] for taking into account the effect of the Coulomb interaction on the tunneling, which is essential for a quantitative comparison. This correction is not rigorous, but it is known to bring the Faisal-Reiss rate in excellent agreement with benchmark results at much weaker intensities than considered here [21].…”

“…We use the correction proposed by Becker et al [21] for taking into account the effect of the Coulomb interaction on the tunneling, which is essential for a quantitative comparison. This correction is not rigorous, but it is known to bring the Faisal-Reiss rate in excellent agreement with benchmark results at much weaker intensities than considered here [21].…”