autoionizing levels in Ca: laser optogalvanic spectroscopy and theoretical analysis |
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Authors: | S Assimopoulos A Bolovinos E Luc-Koenig S Cohen A Lyras P Tsekeris M Aymar |
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Institution: | (1) Atomic and Molecular Physics Laboratory, Physics Department, University of Ioannina, 451 10 Ioannina, Greece, GR;(2) Institute of Accelerating Systems and Applications, P. O. Box 17214, 10024 Athens, Greece, GR;(3) Laboratoire Aimé Cotton, CNRS II, Batiment 505, 91405 Orsay Cedex, France, FR |
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Abstract: | We report the even parity J
=4,5 autoionizing spectra of calcium below the 3d threshold, investigated by two-step laser excitation from the 3d4s metastables
through the 3d4p , intermediate states and subsequent optogalvanic detection. The 3d4s states are populated by electronic collisions in a d.c.
glow discharge sustained in a Ca heat-pipe. More than a hundred resonant transitions have been measured with an accuracy of
for the narrow ones using standard laser calibration techniques. The high lying levels are assigned to all expected autoionizing series. Moreover, some levels are observed. The theoretical interpretation is achieved by a combination of the nearly ab initio eigenchannel R-matrix and multichannel quantum-defect (MQDT) methods as well as by an empirical determination of the MQDT parameters in
the phase-shifted formulation. Theoretical energy level positions and excitation profiles are compared with the experimental
data confirming the identification of the observed structures. Strong mixing between series is found, while the ones do not couple with the series. Further insight into the strong channel mixing in the studied energy range is provided by a comprehensive review
of the excitation profiles in the vicinity of the 4p5p perturber as obtained from a number of intermediate levels used in the present and in earlier experiments. Systematic electron
correlation trends for series of , and are discussed.
Received: 20 November 1997 / Accepted: 15 January 1998 |
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Keywords: | PACS 32 80 RM Multiphoton ionization and excitation to highly excited state (e g Rydberg states) - 32 30 Jc Visible and ultraviolet spectra - 32 80 Dz Autoionization |
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