TKS-VEGA EXPERIMENT - NH AND NH2 BANDS IN COMET HALLEY

Interpretation of the NH band observations of comet Halley on 1986 March 9 results in its production rate Q(NH) = (0.9 +/- 0.3) 10(27) s-1, the lifetimes of NH and its parent at 1 AU, tau = (1.4 +/- 0.5) 10(5) s and tau-p = (1.7 +/- 0.4) 10(4) s, the velocity of radical formation, V = (1.4 +/- 0.5) km/s, and the distance of the unit optical thickness of the coma for NH formation, d = 100 +/- 50 km. The respective data for NH2 are Q(NH2) = (1.8 +/- 0.4) 10(27), tau = (5.3 +/- 1.5) 10(4) s, tau-p = 6 x 10(3) s, V = 0.8 +/- 0.3 km/s, and d = 20 +/- 10 km. With several candidates considered both sets of data can be explained by ammonia as the parent of NH with a yield of 0.08, the rest being NH2, and NH2 as the main parent of NH with a yield of 0.7. The data give the experimental evidence for NH3 as a source of NH and NH2 with a relative abundance of 0.15% in comet Halley.