Four-photon excitation of even-parity Rydberg states in krypton and xenon

Multiphoton ionization via four-photon excitation of high-lying Rydberg states in xenon and krypton has been studied. The p and f series leading to the ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{3/2}^{}{}_{}{}^{}$ ionization limits as well as the p’ and f’ autoionizing levels leading to the ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{1/2}^{}{}_{}{}^{}$ limits have been recorded for both gases. Lower members of the p series in xenon are resolved into p${\left[\mathrm{}\right(5/2\left)\mathrm{}\right]}_2$, p${\left[\mathrm{}\right(3/2\left)\mathrm{}\right]}_2$, and p${\left[\mathrm{}\right(1/2\left)\mathrm{}\right]}_0$ sublevels. Ionization potentials and quantum defects are obtained by a least-squares fitting of the data to the standard Rydberg formula.