“…In the present study this model is employed, with few modifications, to investigate the chemistry of C(ID) atoms and the production of C I 1931 /• emission in the coma of Halley's comet. The modifications are (1) use of laboratory measured cross sections for the process CO + e ---) C + 0 [Cosby, 1993], (2) use of C(ID) + H20 quenching rate coefficient of 1.7X10 'll cm 3 s 'l [Schofield, 1979] During the comet 1P/Halley's exploration the data collected by various spacecraft and ground-satellite-based experiments have indicated that there are many C-bearing species and that carbon is present not only in gas phase but also in solid-dust form (see Grun and Jessberger [1990], Encrenaz and Knacke [1991], Krankowsky [ 1991 ] [Sahnow et al, 1993]. A full quantitative study taking both the solid-dust form and the gaseous form of the coma is very complex and is outside the scope of the present studies.…”