On the chemistry of CS and NS in cometary comae

Abstract We have developed a multifluid chemical model of cometary comae which is an improvement to a recent work by Canaves et al. [Canaves, M.V., de Almeida, A.A., Boice, D.C., Sanzovo, G.C., Nitrogen sulfide in comets Hyakutake (C/1996 B2) and Hale-Bopp (C/1995 O1), Earth Moon Planets, 90, 1–13, 2002.] with the purpose to predict the abundances of carbon monosulfide (CS) and nitrogen sulfide (NS). The model is applied to the recent bright comets Hyakutake and Hale-Bopp at a heliocentric distance of 1 AU using a detailed photo and chemical reaction network including more than 100 species and over 1000 reactions. The collisional reactions have up-to-date rate coefficients from Le Teuff et al. [Le Teuff, Y.H., Millar, T.J., Markwick, A.J., The UMIST database for astrochemistry 1999, A&AS, 146, 157–168, 2000.], while the photolytic rate coefficients were taken for minimum and maximum solar fluxes in order to estimate an lower and a upper limit for the abundances of NS and CS. The comparison of results for NS molecule in comet Hale-Bopp is in good agreement with Irvine et al. [Irvine, W.M., Senay, M., Lovell, A.J., Matthews, H.E., McGonagle, D., Meier, R., Note: detection of nitrogen sulfide in comet Hale-Bopp, Icarus, 143, 412–414, 2000.], while for CS species we show that the abundances do not seem to vary much with the cometocentric distance.