The spin dependence of the excitation of metastable autoionising lithium4P states by electron impact

The authors measured the spin-dependent cross section asymmetry A for the formation of long-lived autoionising 4 P states of lithium by electron impact. The asymmetry is defined as A=( sigma down arrow up arrow - sigma up arrow up arrow )/( sigma down arrow up arrow + sigma up arrow up arrow ) where sigma down arrow up arrow and sigma up arrow up arrow are the cross sections for antiparallel and parallel spins of the colliding electron and atom. The lifetime measurements of Feldman and Novick (1967) suggest that only the 6 Li(1s2s2p) 4 P 5/2 substate contributes to the measured asymmetry. The authors obtain A=-0.47 with a statistical error of +or-0.03 and a systematic error of -0.05/+0.03. This value is slightly lower than the theoretical expectation of A( 4 P 5/2 )=-0.400. A deviation in this direction would occur if the lifetime of the 4 P 1/2 substate were not as short as has been measured in a strong magnetic field but rather were as long as that calculated for zero magnetic field.