Angle-resolved HeIIα photoelectron measurements for the 5d subshells of Hg II, Tl I and Pb II halides

The He II alpha photoelectron spectra for ionisation from the 5d subshells of metal atoms in the Hg II, Tl I and Pb II halides have been recorded at two angles to unpolarised photon beams. From these measurements asymmetry parameters beta for the 5d^-1 ionisation have been determined. The variation of beta with electron kinetic energy is similar to that observed previously for 5d^-1 ionisation of atomic mercury. Differences are attributed to the variation in Z rather than to the molecular environment. The 5d^-1 ionisation energy of TlF is shown to be consistent with a simple classical model of chemical shifts.