Chemiluminescence studies. V. Production of electronically excited alkali atoms in reactions of Li, Na, and Cs with NF3 and of Cs with F2

Abstract

The magnitudes and distributions of alkali atom emission have been measured for Li+NF₃, Na+NF₃, Cs+NF₃, and Cs+F₂ flames. The production of excited states in all cases follows a g_i(E_ion−E_i)³ dependence, where g_i and E_i are the degeneracy and energy of the state, and E_ion is the ionization energy of the alkali atom. This suggests that the primary excitation mechanism involves electron–ion recombination. Examination of other data shows that this energy dependence of excitation may hold in a variety of reaction systems and experimental conditions. Measured photon yields for atomic emission ranged from 0.2% to 3%; considerably higher values would be expected in the absence of radiation trapping. There is no evidence for substantial population inversions between any of the atomic states.