We carried out a high-dispersion spectroscopic observation of the comet C/1999 S4 (LINEAR) on 2000 July 8.75 (UT). The NH2 Ã(0, 10, 0)-X̃(0, 0, 0) and Ã(0, 9, 0)-X̃(0, 0, 0) bands were extracted from the observed spectrum and compared with the modeled spectra. We developed a fluorescence equilibrium model for the NH2, in which Ã(0, v′2, 0)-X̃(0, 0, 0) transitions and the radiative relaxation among the rotational levels in X̃(0, 0, 0) were considered. The rotational structure of the spin doublet (F1 and F2 levels) and the Swings effect were considered in the model. The modeled spectra are consistent with the observed spectra of the Ã(0, 10, 0) and Ã(0, 9, 0) bands. Our results show that the fluorescence excitation and the radiative relaxation processes are dominant for NH2 in a coma of the comet at ∼ 1 AU from the Sun.
- Comets: general
- Comets: individual (C/1999 S4: LINEAR)
- Molecular processes