Role of nuclear spin in photoionization: Hyperfine-resolved photoionization of Xe and multichannel quantum defect theory analysis

Abstract

High-resolution photoionization spectra following single-photon excitation from the $^{1}S_{0}$ ground state have been recorded for the seven most abundant isotopes of xenon in the range between the first $^{2}P_{3∕2}$ and the second $^{2}P_{1∕2}$ ionization thresholds. Accurate values for the ionization energies ${V}_{\text{ion}}(^{2}P_{1∕2})$ and isotope shifts have been derived enabling the determination of the spin-orbit splitting in ${\mathrm{Xe}}^{+}$ with an unprecedented accuracy. The narrow bandwidth of the vuv laser (250 MHz) has enabled the resolution of the hyperfine structure of the autoionizing $n{s}^{\ensuremath{'}}$ series of $^{129}\mathrm{Xe}$ and $^{131}\mathrm{Xe}$ in the range of principal quantum number $n=30\text{--}150$. Multichannel quantum defect theory (MQDT) has been extended to treat the hyperfine structure of autoionizing Rydberg series and to derive the hyperfine structure of the $^{2}P_{1∕2}$ state of the singly charged ion. The MQDT analysis demonstrates the possibility of producing ions in selected hyperfine states by photoionization and enables the characterization of the combined effects of the spin-orbit and hyperfine autoionization.