Resonant formation of Ca{sup +} from the Ca{asterisk}(4{ital s}25{ital d}{sup 1}{ital D}{sub 2}) level explained by autoionization through the 3{ital d}{sub 3/2}9{ital f}{sub 5/2}, {ital J}{sup {pi}}=2{sup {minus}} resonance
- JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 (United States)
The formation of Ca{sup +} ions is measured in an effusive Ca beam by exciting through either the 4{ital s}4{ital p}{sup 1}{ital P}{sub 1} or the 4{ital s}5{ital p}{sup 1}{ital P}{sub 1} state to highly excited Ca{asterisk}(4{ital snd}{sup 1}{ital D}{sub 2}) Rydberg states. In agreement with previous work by McLaughlin and Duquette [Phys. Rev. Lett. {bold 72}, 1176 (1994)], when the Rydberg states are accessed through the 4{ital s}5{ital p}{sup 1}{ital P}{sub 1} state, we detect a large increase in Ca{sup +} ions for {ital n}=25, compared to other high-{ital n} Rydberg states. It had been reported {bold (}Fabrikant [Phys. Rev. A {bold 48}, R3411 (1993)]; McLaughlin and Duquette{bold )} that {open_quote}{open_quote}ground-state{endash}Rydberg-state{close_quote}{close_quote} collisions cause this large increase in ion production and that the result provides a precise value of the electron affinity of Ca through the binding energy of the Rydberg electron. However, a variation of the original experiment in which the same Rydberg states are accessed through the 4{ital s}4{ital p}{sup 1}{ital P}{sub 1} level instead of the 4{ital s}5{ital p}{sup 1}{ital P}{sub 1} level shows no enhancement of ions for any particular Rydberg level. With a three-laser experiment we show that the enhanced ionization effect for the 25{ital d} state is due to the 3{ital d}{sub 3/2}9{ital f}{sub 5/2}, {ital J}{sup {pi}}=2{sup {minus}} autoionizing resonance, which is coincidentally accessed from the Ca(4{ital s}25{ital d}{sup 1}{ital D}{sub 2}) state by the 808-nm photon involved in the original experiment by McLaughlin and Duquette. The existence of this resonance close to the experimentally observed energy is also established by {ital R}-matrix calculations. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 288791
- Journal Information:
- Physical Review A, Journal Name: Physical Review A Journal Issue: 2 Vol. 54; ISSN 1050-2947; ISSN PLRAAN
- Country of Publication:
- United States
- Language:
- English
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