Three-photon excitation of autoionizing states of atomic xenon between the ${}_{}{}^2{}_{}{}^{}\mathrm{°}_{3/2}^{}{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{°}_{1/2}^{}{}_{}{}^{}$ fine-structure thresholds

The nonresonant, three-photon ionization spectrum of atomic Xe in the region between the ${\mathrm{Xe}}^{+}$ ${}_{}{}^2{}_{}{}^{}\mathrm{}_{3/2}^{}{}_{}{}^{}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{}_{1/2}^{}{}_{}{}^{}$ fine-structure limits is reported. Using linearly polarized light, four autoionizing Rydberg series are observed converging to the ${\mathrm{Xe}}^{+}$ ${}_{}{}^2{}_{}{}^{}\mathrm{}_{1/2}^{}{}_{}{}^{}$ limit, corresponding to ${(}^2$P°${\mathrm{}}_{1/2}$)ns’[(1/2)]°${\mathrm{}}_1$, (2P°${\mathrm{}}_{1/2}$)nd’[(3/2)]°${\mathrm{}}_1$, ${(}^2$P°${\mathrm{}}_{1/2}$)nd’[(5/2)]°${\mathrm{}}_3$, and ${(}^2$P°${\mathrm{}}_{1/2}$)ng’[(7/2)]°${\mathrm{}}_3$; as expected, using circularly polarized light only the J=3 series are observed. These results are in contrast to earlier experimental work in which no resonant structure was observed. Photoelectron angular distributions are reported for the ${(}^2$P°${\mathrm{}}_{1/2}$)9s’[(1/2)]°${\mathrm{}}_1$ and the ${(}^2$P°${\mathrm{}}_{1/2}$)7d’[(3/2)]°${\mathrm{}}_3$ autoionizing resonances. The results are compared with the recent theoretical calculations by P. Gangopadhyay et al. [Phys. Rev. A 34, 2998 (1986)].