Resonantly enhanced multiphoton-ionization photoelectron spectroscopy of krypton and xenon: Experiment and theory.

Abstract

Angular distributions for energy-resolved photoemitted electrons from resonantly enhanced multiphoton ionization (REMPI) via the two-photon allowed 6p[j=1/2${]}_{\mathit{J}=0}$, 6p[3/2${]}_{2}$, 6p'[1/2${]}_{0}$, 6p'[3/2${]}_{2}$, 7p[1/2${]}_{0}$, 7p[3/2${]}_{2}$, and 7p[5/2${]}_{2}$ states and the three-photon allowed 7s[3/2${]}_{1}$, 8s[3/2${]}_{1}$, 9s[3/2${]}_{1}$, 5d[3/2${]}_{1}$, 5d'[5/2${]}_{3}$, and 5d'[3/2${]}_{1}$ states of xenon and the three-photon allowed 5s[3/2${]}_{1}$, 6s[3/2${]}_{1}$, 4d[3/2${]}_{1}$, 4d[5/2${]}_{3}$, and 4d[7/2${]}_{3}$ states of krypton are reported. In one case, two-photon resonant, three photon ionization [(2+1) REMPI] of the 6p'[1/2${]}_{0}$ state of xenon, a dramatic laser-power dependence (power \ensuremath{\sim}1.5\ifmmode\times\else\texttimes\fi{}${10}^{10}$ to \ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}${10}^{10}$ W/${\mathrm{cm}}^{2}$), was observed. The measured angular distributions for electrons leaving either ion core ${(}^{2}$${\mathit{P}}_{1/2}$ or $^{2}$${\mathit{P}}_{3/2}$) are compared with those calculated from multichannel quantum-defect theory.Reasonable agreement is obtained in reproducing the general features of the angular distributions for the p and d states in the rare gases. However, discrepancies are observed for some of the s states. Comparison of the measured and calculated branching ratios for leaving either ion core also shows good agreement for the p and d states, but shows that there are inadequacies in the theory for describing the s states. We also report the photoelectron energy and angular distributions for the (4+1) REMPI process via the 6p[1/2${]}_{0}$ and 6p[3/2${]}_{2}$ states of xenon. Photoelectrons due to above-threshold ionization, (4+2), resonantly enhanced via the four-photon allowed 6p[1/2${]}_{0}$ state, are also observed.