Spin polarisation of photoelectrons ejected from unpolarised atoms

The photoelectrons ejected from unpolarised atoms by polarised or unpolarised light are usually spin polarised. The polarisation for the (nl)N subshell, with l>or=1 and 1<or=N<or=4l+2, arises from spin-orbit splitting at the initial and (or) final states. To observe this polarisation it is necessary to select the photoelectrons corresponding to the transition from a particular fine-structure level of the initial state to a particular fine-structure level of the final state. The effect exists at all photon energies. The degree of polarisation depends on the energy and polarisation of the photons, the angle of electron ejection and the atomic characteristics. After integration over the electron ejection angles the degree of polarisation becomes equal to zero when unpolarised or linearly polarised light is absorbed and remains non-zero for absorption of circularly polarised light. The degree of polarisation of the photoelectrons ejected from the 2p6 and 3p6 subshells of Ar and the 4d10 and 5p6 subshells of Xe, calculated in the random-phase approximation with exchange, is presented.