Improvements in the generation and detection of Kr(3P) and Kr(3P2) atoms in a flow reactor: Decay constants in He buffer and total quenching rate constants for Xe, N2, CO, H2, CF4, and CH4

Abstract

The generation and decay of Kr(3P2) and Kr(3P0) atoms in a flowing afterglow reactor at 300 K using He carrier gas have been characterized and compared with Ar carrier gas. The dominant loss for the Kr(3P2) and Kr(3P0) atoms in He is diffusion to and quenching at the wall; the two-body quenching constants are of the order of 1×10−15 cm3 s−1 for each. The Kr(3P0) concentration in He carrier was sufficiently high that the total quenching rate constants were measured without resorting to optical pumping from the lower energy Kr(3P2) state. Room temperature rate constants are reported and the product states are discussed for the Kr(3P2) and Kr(3P0) reactions with Xe, CO, N2, H2, CF4, and CH4; the difference between the Kr(3P0) and Kr(3P2) rate constants for N2 is nearly a factor of 6. Quenching rate constants for 13CO are ∼25% smaller than those for 12CO. The Kr(3P0) reaction with CO gives mainly CO(b 3Σ+) and (e 3Σ−); the CO(b, v′=0) level is much more rotationally excited than CO(b, v′=1). Excitation-transfer to Xe from Kr(3P2) gives mainly Xe(6p[3/2]2 and [3/2]1 ); the Kr(3P0) reaction favors the Xe(7s) states. A systematic study of the best electrode configuration and operating conditions for the dc discharge using He carrier gas is reported for the generation of Xe(3P2), Ne(3P0) and Ne(3P2), as well as Kr(3P2) and Kr(3P0).