Spin Orientation of Photoelectrons Ejected by Circularly Polarized Light

Photoelectrons emitted by Cs vapor exposed to circularly polarized light with $2750\lesssim \lambda \lesssim 3150$ Å should have spin orientation $\gtrsim 85\%$ parallel to the light's angular momentum. Measurements of this orientation along the spectrum may be represented by a parameter $x$ defined theoretically in terms of a Hilbert transform of the spectrum of unperturbed dipole matrix elements weighted by the effect of spin-orbit interaction. The theory of this parameter is adapted from Fermi's interpretation of doublet intensity ratios and from Seaton's related interpretation of photoabsorption minima. Semiquantitative estimates are drawn from experimental data on photoabsorption.