Collisional transfer rates between excited levels in helium

In an electron-beam plasma selective excitation by pulsed-dye-laser pumping has been used to study excitation transfer by electronic collisions. In particular, rate coefficients for the transitions 4¹P→4¹S and 3¹P→3¹S have been derived as well as the total deexcitation rate coefficient by Δn≠0 collisions of the 4¹P and 4³D levels. The agreement with theoretical values is within the experimental uncertainties. The effective excitation transfer between the $n=4$ singlet and triplet levels is higher than expected by about two orders of magnitude.