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

Angular distributions for energy-resolved photoemitted electrons from resonantly enhanced multiphoton ionization (REMPI) via the two-photon allowed 6p[j=1/2]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 {~}1.5×{}10¹⁰ to {~}3×{}10¹⁰ W/cm²), was observed. The measured angular distributions for electrons leaving either ion core (²{P}1/2$ or $²P3/2) 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.