DEEXCITATION OF HELIUM 21S AND 23S ATOMS IN FAST COLLISIONS WITH NORMAL HELIUM ATOMS

Cross sections for deexcitation of helium 2S1 and 2S3 atoms in collisions of a helium metastable atomic beam with normal helium atoms have been measured in the laboratory energy range 150-2200 eV. The singlet cross sections are from 20 to 75% larger than the triplet cross sections. Both cross sections were found to obey the general relationship Q12=a-blnv with an oscillatory structure superimposed upon this monotonic velocity dependence. The magnitude of the triplet cross sections compare favorably with calculated values of the cross section for the symmetric excitation-transfer reaction between 2S3 and 1S1 atoms. © 1969 The American Physical Society.