Strong Laser Fields
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Unexpected fine-structure distribution in 3+1 photon-ionization of Xe
C. Bordas1, M. J. Dyer1, T. Fairfield1, H. Helm1 and K. C. Kulander2
1Molecular Physics Laboratory, SRI International, Menlo Park, California 94025
2Joint Institute for Laboratory Astrophysics, University of Colorado at Boulder, Boulder, Colorado 80309
Lawrence Livermore National Laboratory, Livermore, California 94551


Three-photon resonance enhanced four-photon ionization of xenon shows preferential formation of Xe+(2P1/2) when intermediate ns[3/2]1 Rydberg states are excited in the three-photon step. Here, the nl[K]J notation refers to jcl coupling, in which the angular momentum of the ion core, jc, is coupled to the orbital angular momentum of the Rydberg electron l to give K, which is then coupled to the Rydberg electron's spin to give J. The primes following l denote states belonging to the 2P1/2 core. Multichannel-quantum-defect theory identifies these intermediates as nearly pure Rydberg states belonging to the Xe+(2P3/2) core. An equivalent behavior is found for the 7s'[1/2]1 intermediate state which preferentially produces Xe+(2P3/2). On the other hand, for nd and nd' resonances we observe final-state distributions which closely mirror the core character of the intermediate state. The suppression of the parent core channel for s-type Rydberg states is shown to be due to a Cooper minimum in the ns--> εp transition amplitudes. As a consequence, minor components of the resonance state wave functions play a major role in the selection of the final ionization channel, in particular via the much larger amplitudes of nd'--> εf' transitions. ©1995 The American Physical Society

©1995 Phys. Rev. A 51, 3726-34 (1995)

DOI: 10.1103/PhysRevA.51.3726
PACS: 33.80.-b

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