Observation of 3p(5)nd J = 2, 3 odd parity spectra of argon and MQDT analysis in the discrete and autoionizing regions

We report new measurements of the spectra of argon in the discrete and auto ionizing region using two-step laser excitation and optogalvanic detection technique. By selecting a particular intermediate level, we have been able to isolate a Rydberg series of specific K and J values. The 3p(5)nd[3/2](2) , 3p(5)nd[5/2](2) and 3p(5)nd[5/2](3) Rydberg series, converging to both 3p (5)(P-2(3/2)) and 3p(5)(P-2(1/2)) limits have been excited from the 3p(5)4p [(1/2)](1), 3p(5)4p[(3/2)](1) and 3p(5)4p[(3/2)](2) intermediate levels whi ch are being populated from the 3p(5)4s[(3/2)](2) metastable level. The thr ee perturbers 3p(5)(P-2(1/2))8d'[3/2](2), 3p(5)(P-2(1/2))8d'[5/2](2) and 3p (5)(P-2(1/2))8d'[5/2](3) are clearly identified and their interactions with the respective series have been studied using multichannel quantum defect theory. The parameters obtained by fitting the lines shapes of the correspo nding autoionizing resonances adjacent to the first ionization threshold 3p (5)(P-2(1/2))9d'[3/2](2), 3p(5)(P-2(1/2))9d'[5/2](2) and 3p(5)(P-2(1/2))9d' [5/2](3), show good correlation with those determined from the series pertu rbation analysis in the discrete region. It is remarked that only a two cha nnel quantum defect model is sufficient to describe the series perturbation s and the autoionization phenomena. (C) 1999 Elsevier Science B.V. All righ ts reserved.