The Spectral Development of Comet P/halley from 1985 August to 1986 June

A series of spectra of comet P/Halley has been obtained every month during its recent apparition, starting 1985 August and ending 1986 June. The spectra cover the wavelength region from 5200 to 10400 Å at a spectral resolution of ≡12 Å. Their spatial extent is 200arcsec along the slit. A variety of spatially resolved spectra with the slit along the tail and perpendicular to the tail were recorded. Emission species observed in this wavelength range are C₂, CN, NH₂, H₂O⁺, [O I] and Na I. The authors have detected the 2-0 C₂ Phillips band at 8750 Å, and from its intensity ratio of 1/9 to the 0-1 Swan band derive a preliminary C₂ singlet to triplet intercombination probability of <10^-7. Na emission was observed strongly only in the 1986 March data. During 1985 August and September, a number of emission features were seen which are not yet identified.