Jb. Boffard et al., Measurement of electron-impact excitation cross sections out of metastablelevels of argon and comparison with ground-state excitation, PHYS REV A, 59(4), 1999, pp. 2749-2763
This paper reports the results of measurements of cross sections for electr
on excitation out of the 1s(3) and 1S(5) metastable levels of argon (the J
= 0 and 2 levels, respectively. of the 3p(5)4s configuration) into eight of
the ten levels of the 3p(5)4p manifold. The metastable atoms were generate
d by two methods: (a) an atomic beam emerging from a hollow-cathode dischar
ge, and (b) charge-exchange collisions between a fast argon-ion beam and ce
sium atoms. The metastable argon atoms are excited by a crossed electron be
am into the 3p(5)4p levels and the emissions from these levels are utilized
to determine the cross sections. Removal of the 1s(5) atoms in the hollow-
cathode discharge experiment by means of laser pumping allows us to determi
ne the separate contributions from each metastable level to the observed fl
uorescence signal. The magnitudes of:the cross sections for excitation out
of the metastable levels into the different levels of the 3p(5)4p manifold
vary vastly. The patterns of the observed variations are interpreted by mea
ns of a multipole analysis. This multipole model is also used to discuss th
e comparison of excitation cross sections out of the metastable levels with
those out of the ground level. [S1050-2947(99)01204-4].