EMISSION OF HEH+ IN NEBULAE

The formation and destruction processes of HeH+ in nebulae are discuss ed, and calculations of the abundances of HeH+ are presented. It is sh own that for effective temperatures of the ionizing source exceeding 5 0,000 K, the abundances are of the order of 10(12) cm-2, largely indep endent of the nebular parameters. The emission-line intensities increa se approximately as the density of the nebula. Results are given for t wo detailed models of the planetary nebula NGC 7027. The predicted int ensities exceed the observational upper limit. The emissions have shar ply peaked distributions with maximum intensity reached in a narrow zo ne at the edge of the ionized region. The greater art of the emission may be outside the region observed.