Accurate comparison of Hel, NeI photoionization and He(23, 1 S), Ne(3s 3 P s,3 P 0) penning ionization of argon atoms and dimers

1434-6079

36.40.+d ; 34.50.-s ; 34.50.Gb ; 33.80.Eh ; 82.40.Dm

Springer Online Journal Archives 1860-2000

Physics

Abstract Using crossed beams and mass spectrometric ion detection, we have investigated the ionization of argon atoms and dimers in a skimmed supersonic beam by HeI (58.4 nm) and NeI (73.6, 74.4 nm) photons and by He(23,1 S) and state selected Ne(3s 3 P 2,3 P 0) metastable atoms. The cross section ratioq 22/q 1 (i.e. the cross sectionq 22 for formation of Ar 2 + ions from Ar2 divided by the total ionization cross sectionq 1 for Ar atoms), arbitrarily normalized to 1 for HeI impact, is found to vary weakly as follows: HeI/NeI/He(23, 1 S)/Ne(3 P 0)Ne(3 P 2)=1/1.136(9)/0.893(4)/1.034(12)/0.985(9). The results are qualitatively interpreted using available information on the intermolecular potentials and the two different ionization processes. The observation thatq 22/q 1 is 5% larger for Ne(3 P 0) than for Ne(3 P 2) is attributed to anomalies in the respective branching ratios for formation of the Ar+(2 P 3/2)/Ar+(2 P 1/2) ion states in conjunction with differences in the stability of the formed Ar-Ar+(2 P 3/2) and Ar-Ar+(2 P 1/2) molecular ions.

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