부산대학교 도서관

This is a study of the deexcitation mechanisms of the metastable 5 /sup 2/D/sub 3//sub ///sub 2/ state of Ba/sup +/ in about 1 atm He buffer gas in the temperature range of 500--650 /sup 0/C. The ions were produced by three-photon ionization with light tuned to a resonance between two excited states of Ba, enabling the electron density to be varied independently of the temperature and pressure. The deexcitation is dominated by superelastic scattering of electrons with a cross section of sigma/sub se/ = 45 +- 20 A/sup 2/ (corresponding to an electron-impact excitation cross section of 11 A/sup 2/) and quenching by Ba atoms with a cross section of sigma/sub Ba/ = 130 +- 25 A/sup 2/. No dependence of the deexcitation rate on He density was detected, and we infer an upper limit on the cross section of sigma/sub He/ less than or equal to9 x 10/sup -22/ cm/sup 2/.