Rotational Temperature Modeling of the Swan Δν = 0 Band Sequence in Comet 122P/de Vico

We modeled observations of the C2 d3Πg–a3Πu (Swan) Δν = 0 sequence observed in spectra of comet 122P/de Vico obtained with the 2.7 m Harlan J. Smith Telescope and Tull Coude spectrograph of McDonald observatory on 10/3/1995 and 10/4/1995. The data used spanned 4986–5169 Å at R = λ/Δλ = 60 000. We used the PGOPHER molecular spectra model to generate and fit synthetic spectra with the d3Πg having one and two rotational temperatures. We found that the excited state had a two-component rotational temperature, similar to that found for comet Halley. The modeled spectrum was sufficiently high quality that local perturbations were important to include. The large perturbation, b3Σg–(ν = 10), was added to our fits, and some new estimates of its molecular constants were found.