Strong field detachment of a negative ion with non-zero angular momentum: application to F-

We apply our recently developed, model-independent quantum approach for intense laser detachment of a weakly bound electron to interpret a recent experiment on abovethreshold detachment (ATD) of the Fion. We find that the measured electron energies correspond to the “Keldysh part” of the ATD spectrum, just below the onset of our predicted rescattering plateau. Overall, our predicted ATD spectrum (using a scaled peak intensity and focal averaging) is in excellent agreement with the experimental data, except for certain structures observed for electron energies above 12.6 eV that we attribute to known two-electron resonances of F-. A number of analytical approximations to our exact p-state ATD amplitude are obtained, and their accuracy is investigated. There are only a few analytical models that are widely used in laser-atom physics to describe strong field ionization and detachment processes. The simplest of them is the Keldysh approximation (KA) [1], which is valid for the tunneling regime. The most spectacular feature in ATI and ATD spectra, the broad plateau in the yield of high-energy electrons, originates from the rescattering of the active electron by the parent ion or atom. It requires for its description a more exact, beyond-KA account of the binding potential U(r). A few such treatments have been introduced. An “improved” version of the KA (IKA) [2], that includes first-order in U(r) corrections to the KA, has been used to interpret experiments for inert gases, as reviewed in [3]. Quasiclassical analyses of rescattering effects have become popular recently; they interpret high-energy plateau features in terms of classical trajectories [3]. Finally, a fruitful model for analyzing strong field effects beyond the KA is the zero-range potential (ZRP) model, which (within the quasistationary quasienergy states (QQES) approach [4]) permits an accurate, ab initio formulation of the problem as well as essentially exact numerical results [5, 6]. However, the above mentioned beyond-KA analyses are valid only for s-electron initial states and thus do not allow one to analyze the dependence of ATI or ATD features on the spatial symmetry of the initial state. Very recently [7], a model-independent approach has been developed for strong field detachment of a weakly bound electron having