Inner-shell photoemission from the iodine atom inCH3I

The first photoemission measurements of the I $4d$ and I " $4p$ " subshells in methyl iodide are presented. Cross sections and angular-distribution asymmetry parameters were measured from threshold to 300 eV photon energy for the I $4d$ level (to 440 eV for the asymmetry parameter), and from 175 to 300 eV for the I " $4p$ " level. The I $4d$ results exhibited atomiclike behavior throughout this energy range, mimicking the behavior of the Xe $4d$ subshell. Theoretical calculations for the Xe $4d$ subshell agree very well with the I $4d$ asymmetry-parameter results, indicating that the I $4d$ subshell is localized on the iodine atom in ${\mathrm{CH}}_3$I. Nearer to threshold, the spin-orbit final states, ${4d}_{\frac{5}{2}}$ and ${4d}_{\frac{3}{2}}$, were resolved and exhibited nonstatistical intensity ratios mainly due to a kinetic energy effect. The I " $4p$ " asymmetry-parameter results were found to be essentially identical to the asymmetry-parameter results for the I $4d$ subshell at the same photon energies, suggesting strong interchannel coupling. This result is discussed with respect to collective effects in the iodine $N$ shell.