Cascade production of Ar(3p54p) following electron bombardment

We observe the time dependence of the fluorescence of Ar(3p54p) following electron excitation of argon at pressures from 2–3000 Torr. The population of these levels at the lowest pressures observed is dominated by radiative cascade from Ar(3p53d) and Ar(3p55s). For argon states 4p′[1/2]0, 4p′[3/2]2, and 4p[1/2]0 we find the cascade transitions can be identified and we assign radiative lifetimes of 61±10, 69±12, and 61±6 nsec to 3d′[3/2]1, 3d′[5/2]3, and 3d[3/2]1, respectively. For cascade lifetimes to other levels, unique assignments cannot be made until values for forbidden electron impact cross sections to 3p53d and 3p55s can be obtained. The collisional quenching rates for the cascading levels are measured and found to explain the pressure dependence of the decay of Ar(3p54p) over the full range of pressure except for Ar(3p54p′[1/2]1) which has a unique and interesting behavior at high pressures.