We modeled observations of the C _ { 2 } \mathrm { d } ^ { 3 } \Pi _ { g } - \mathrm { a } ^ { 3 } \Pi _ { u } ( Swan ) \Delta \nu = 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 10/03/1995 and 10/04/1995 .
The data used spanned 4986-5169 Å at R = \lambda / \Delta \lambda = 60,000 .
We used the PGOPHER molecular spectra model to generate and fit synthetic spectra with the d ^ { 3 } \Pi _ { g } having one and two rotational temperatures .
We found 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 , b ^ { 3 } \Sigma _ { g } ^ { - } ( \nu = 10 ) , was added to our fits and some new estimates on its molecular constants were found .