Spin-orbit effects in atomic high-harmonic generation

Spin-orbit interactions lead to small energy gaps between the outermost p(1/2) and p(3/2) shells of noble gas atoms. Strong-field pulses tunnel-ionize an electron out of either shell resulting in spin-orbit-driven hole motion. These hole dynamics affect the high-harmonic generation (HHG) yield. However, the spectral shape as well as the angular distribution of the HHG emission is not influenced by spin-orbit coupling. We demonstrate the spin-orbit effect on atomic krypton by solving the multi-electron Schrodinger equation with the time-dependent configuration-interaction singles approach. We also provide pulse parameters where this effect can be identified in experiments through an enhancement in the HHG yield as the wavelength of the strong-field pulse increases.