Using transverse resonant two-photon, single-mode laser excitation of metastable 40Ar(4s 3P2) atoms in a collimated beam in combination with a calibrated travelling Michelson interferometer involving digital fringe interpolation, we have measured the energies for the Ar(4p, J = 3 → nd, J = 4) transitions with principal quantum numbers n = 12-100 with a relative uncertainty of 8 × 10-8. The Rydberg atoms are formed in a region of low electric and magnetic fields and detected by electron transfer to SF6 molecules in a skimmed supersonic beam. A single-channel quantum defect analysis of the experimental data is performed, revealing weak perturbations of the n = 12 and 20 levels by interaction with the Ar(2P 1/2 7g′, J = 4) and Ar(2P 1/2 8g′, J = 4) levels, respectively. The value for the ionization energy of the 40Ar+(2P3/2) limit has been determined as 21 647.076(2) cm-1 relative to the 40Ar(4p, J = 3) level and as 127 109.836(3)(±0.05) cm-1 relative to the ground state of 40Ar (see also note added in proof). Low-lying autoionizing ng′, J = 4 resonances (n = 9-13) have been investigated and their quantum defects and reduced width determined for the first time. A multichannel quantum defect theory analysis yields an estimate (0.76 cm-1) for the energy separation between the perturbed 20d level and the perturbing 8g′ level, predicts the transition intensity to the 8g′ level to be much weaker than that to the 20d level and shows that the g′-g coupling in the autoionization region is much stronger than the g′-d coupling determined from the 8g′-induced perturbation in the discrete nd, J = 4 spectrum.
|Number of pages||16|
|Journal||Journal of Physics B: Atomic, Molecular and Optical Physics|
|Publication status||Published - 1999 May 28|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics