A general approximator for strong-field ionization rates

We address the long-standing problem of determining accurate, time-resolved ionization rates for atoms in strong laser fields, a quantity that is fundamental to attosecond science. We show that it is possible to retrieve sub-optical-cycle dynamics of strong-field ionization from ionization probabilities obtained for a set of few-cycle laser pulses that covers a sufficiently broad parameter space. To this end, we introduce the General Approximator for Strong-Field Ionization Rates (GASFIR), a retrieval tool that uses a few adjustable parameters to accurately reconstruct ab initio data. By imposing only essential physical constraints, our model provides a versatile framework for time-domain investigations of strong-field ionization and the role of ionization dynamics in attosecond metrology and lightwave electronics.

💡 Research Summary

The paper tackles a long‑standing challenge in strong‑field physics: obtaining accurate, time‑resolved ionization rates for atoms exposed to intense laser fields. While ionization probabilities can be computed reliably with ab‑initio methods such as the time‑dependent Schrödinger equation (TDSE), extracting an instantaneous rate Γ(t) from these probabilities has been problematic because the strong field blurs the distinction between bound and continuum parts of the wavefunction. Conversely, analytical strong‑field approximations (SFA) provide explicit rate formulas but lack quantitative accuracy, especially when Coulomb, Stark, or multi‑electron effects become important.

The authors propose a new retrieval framework called the General Approximator for Strong‑Field Ionization Rates (GASFIR). They define an ionization‑rate functional E(t) → Γ(t) that must satisfy two essential criteria: (i) it must reproduce the exact ionization probability via P = 1 – exp