Even parity series of argon Rydberg states studied by fast-beam collinear laser spectroscopy

Abstract

The authors have applied the collinear laser spectroscopy technique together with a field ionisation detection method to investigate the even parity spectra of atomic argon. The optical excitation is produced by a frequency doubled CW ring dye laser operating in the 300 nm region. The 4s(3/2)20 metastable level populated by means of charge exchange collisions with sodium vapour was chosen to be the starting level in the one-photon excitation process. Two hundred and forty one levels belonging to the 3p5np and 3p5nf configurations has been measured with an absolute accuracy of 0.02 cm-1. The first ionisation limit has been redetermined to be I32/=127 109.88+or-0.02 cm-1 and a MQDT (multichannel quantum defect theory) treatment of the whole series has been performed, completing the previous studies of odd spectra. In addition, some details are given concerning the sensitivity, the advantages and limitations of this method.