On the selective multiphoton ionization of sodium by femtosecond laser pulses: A partial-wave analysis

TL;DR

This study investigates sodium's multiphoton ionization using femtosecond laser pulses, combining numerical simulations and experiments to analyze photoelectron spectra and demonstrate selective ionization via specific intermediate states.

Contribution

It provides a detailed partial-wave analysis of spectral peaks, revealing the potential for laser intensity-controlled selective ionization through different intermediate states.

Findings

Numerical spectra agree with experimental results.

Spectral peaks are superpositions of contributions from various intermediate states.

Selective ionization is achievable at specific laser intensities.

Abstract

Multiphoton ionization of sodium by femtosecond laser pulses of 800 nm wavelength in the range of laser peak intensities entering over-the-barrier ionization domain is studied. Photoelectron momentum distributions and the energy spectra are determined numerically by solving the time dependent Schroedinger equation for three values of the laser intensity from this domain. The calculated spectra agree well with the spectra obtained experimentally by Hart et al (Phys. Rev. A 2016 93 063426). A partial wave analysis of the spectral peaks related to Freeman resonances has shown that each peak is a superposition of the contributions of photoelectrons produced by the resonantly enhanced multiphoton ionization via different intermediate states. It is demonstrated that at specific laser intensities the selective ionization, which occurs predominantly through a single intermediate state, is possible.