Measurements of self broadening of the triplet line λ706.5 nm in helium

Measurements of spectral profiles of the fine structure components of the helium line lambda 706.5 nm (1s2p 3 P 2,1,0 -1s3s 3 S 1 ) from a gas discharge have been carried out at temperatures of 77 and 300 K over the pressure range of 0.5 to 9.0 Torr using a scanning Fabry-Perot interferometer. The analysed Lorentzian components vary linearly with gas number density as predicted by standard line broadening theory, with no evidence of profile distortions previously observed in the corresponding singlet lines. There is also no evidence of asymmetry of the individual profiles consistent with the theory of overlapping lines developed by Baranger (1958). As expected, the broadening constants of typically (83+or-2)*10 -23 MHz m 3 /atom (77 K) and (137+or-13)*10 -23 MHz m 3 /atom (300 K) are significantly smaller than those of corresponding resonance broadened singlet lines and are dependent on temperature.