Angle resolved photoelectron spectroscopy of the valence shells in HI and CH3I as a function of photon energy from 13 to 90 eV

Abstract

Angle‐resolved photoelectron spectroscopy was carried out on the valence shells of HI and CH₃I over a photon energy range of 13–90 eV with the use of synchrotron radiation. From these data, partial cross sections and angular distribution parameters were obtained for bands corresponding to the 1 ²Π and 1 ²Σ⁺ states of singly ionized HI and the 1 ²E, 1 ²A and 2 ²E states of singly ionized CH₃I. Calculations were carried out on HI for the same parameters with the use of the multiple scattering Xα method. The results, both experimental and theoretical, are examined in terms of the Cooper minimum. Clear evidence for minima in both the cross sections and β values are found for the lone‐pair orbitals. Bonding orbitals involving the iodine 5p subshell also show minima in the energy dependence plot of the β values, but the effects are less pronounced. These results are compared with similar studies on chlorine‐containing molecules. The lone‐pair orbitals showed spin‐orbit resolved bands in the photoelectron spectra. The behavior of these spin‐orbit split states are examined for their differences in β values and branching ratios as a function of photon energy up to 35 eV.