Electron excitation coefficients of neutral and ionic levels of krypton in Townsend discharges

Abstract

In this paper, we present experimental results for excitation coefficients of krypton atoms to several Kr and Kr + excited levels for E/ N (electric field to gas particle number density ratio usually in units of Townsend, 1 Td = 10 − 21 V m 2) values from 7 × 10 − 20 V m 2 to above 1 × 10 − 17 V m 2. The data have been obtained in two different parallel plate self-sustained Townsend discharge drift tubes. The spatial distribution of the emission intensities were recorded and then normalized to give excitation coefficients at the anode, by using the electron flux at this point. The values of these coefficients are placed on an absolute scale by using a standard tungsten ribbon lamp calibrated against a primary blackbody radiation standard. The ionization rates at different E/ N are obtained from the spatial emission profiles. The data for atomic krypton levels 2p 2, 2p 3, 2p 5, 2p 6, 2p 7, 2p 8, 3p 5 and 3p 6 (in Paschen notation) were converted to excitation coefficients by using quenching coefficients from the literature. The emission coefficients of eight 4s 24p 4 ( 3P)5p levels of Kr + have also been measured for E/ N values from about 1 × 10 − 18 V m 2 up to nearly 8 × 10 − 18 V m 2.