Self-broadening of triplet lines of helium

The self-broadening of the helium triplet lines 23S1-33P2,1,0, 23P2,1,0-n3S1 and 23P2,1,0-n3D3,2,1 for n = 3,4,5 at temperatures of 80 K and 300 K is calculated using a semiclassical impact model of pressure broadening. The collision between the excited helium emitter and ground state helium perturber is described in terms of adiabatic molecular potentials based upon model potential expressions for the interacting atoms. For the triplet lines for which experimental results are available, the calculated widths are too high by an average of 20%. However, imposition of a lower cutoff on impact parameters in order to exclude perturber paths entering classically forbidden regions of the interaction significantly improves the agreement with experiment. (author)