Spin Polarization in Strong-Field Ionization as Sensor of Trapped Electron Orbits
Phys. Rev. Lett. 135, 193201 – Published 6 November, 2025
DOI: https://doi.org/10.1103/9f8y-td77
Abstract
We show how spin polarization of photoelectrons produced in strong-field ionization of noble-gas atoms can be used to detect highly unexpected electron orbits created in strong, circularly polarized near-infrared fields. In such fields, ionization is expected to generate photoelectrons rapidly moving away from the ionic core, freezing their initial spin due to the short-range nature of the spin-orbit interaction between the photoelectron and the core. However, we find clear evidence of spin flips in the photoelectron spectra at low photoelectron energies and confirm that they happen because a photoelectron has been trapped near the core. The presence of such highly unexpected orbits explains the marked deviations between the recent experimental measurements of spin polarization [Nat. Photonics 10, 526 (2016)] and simulations with frozen spin.
