Spin-Polarized Photoelectrons in the Vicinity of Spectral Features

It has been shown by Fano [1] that photoionization of a cesium atom by a laser pulse tuned to the vicinity of a Cooper minimum generates spin-polarized electrons. Here we show that while photoionization of rare gases does not provide large spin polarization in the vicinity of the Cooper minimum, the Fano resonances yield much higher overall spin polarization (≥40%). The spin polarization increases in angle-resolved photoelectron spectra, and reaches 100% when measured in coincidence with the photoion. A common feature of both Cooper minima and Fano resonances, is the large variation of the photoinization cross section over photon energy, which proves to be vital for efficient generation of spin-polarized electrons. We provide a general framework for achieving spin polarization in photoionization irrespective of the ionization regime.