Jb. Kingdon et Gj. Ferland, THEORETICAL HE-I LINE-INTENSITIES IN GASEOUS NEBULAE - NGC-1976, NGC-6572 AND IC-4997, Monthly Notices of the Royal Astronomical Society, 282(3), 1996, pp. 723-725
Smits has recently calculated theoretical He I intensities for a large
number of lines for conditions appropriate to gaseous nebulae. These
are likely to remain the definitive calculations for some time to come
. A comparison of these line ratios with observed values in three nebu
lae reveals some discrepancies. We show that these discrepancies are r
educed when collisional effects from the metastable 2(3)S level are in
cluded, and that it is not necessary to invoke an unknown depopulation
mechanism for the He I 2(3)S level.