Decay of Excited Species in a Pulsed Discharge in Krypton

Abstract

The emission in the afterglow of a pulsed discharge in krypton has been investigated. Measurements of the decay times of the resonance radiation at $\lambda 1236$ Å and a diffuse molecular radiation at $\lambda 1250$ Å and longer wavelengths have been made as functions of pressure at 295 and 196°K. The measurements have been interpreted on the assumption of a simple two-time-constant model, leading to values of the collision frequencies for collision-induced transitions between the metastable level ($1s_5$) and the resonance level ($1s_4$) of 13×${10}^{-14\mathrm{}}$ ${\mathrm{cm}}^3$/sec and 22×${10}^{-14\mathrm{}}$ ${\mathrm{cm}}^3$/sec at 295 and 196°K, respectively, for de-exciting collisions ($1s_4-1\mathrm{}{s}_5$), and 7.6×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^3$/sec and 1.3×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^3$/sec, respectively, for exciting collisions ($1s_5-1\mathrm{}{s}_4$). The coefficients for the conversion of metastable atoms to molecules in two- and three-body collisions with normal atoms has also been determined. The two-body collision frequency for molecule formation was found to be 15×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^3$/sec and 26×${10}^{-16\mathrm{}}$ ${\mathrm{cm}}^3$/sec at 295 and 196°K, respectively, and the three-body collision frequency was found to be 4×${10}^{-32\mathrm{}}$ ${\mathrm{cm}}^6$/sec and 6.9×${10}^{-32\mathrm{}}$ ${\mathrm{cm}}^6$/sec at 295 and 196°K. The results are compared with existing measurements in other rare gases. The two-body part of the molecule formation is discussed in terms of an interatomic potential which has a hump similar to that proposed in the case of helium.