Neutral cometary atmospheres. III - Acceleration of cometary CN by solar radiation pressure

The acceleration of cometary CN radicals due to solar radiation pressure has been determined by fitting Monte Carlo models to nine observed sunward-tailward pairs of brightness profiles of the (0-0) band of CN at 3883 A. The profiles were determined from spectrograms of comets Bennett 1970 II and West 1976 VI. The values of the observed acceleration agree with those computed from resonance fluorescence calculations to within the expected uncertainties. This provides an independent confirmation of the identification of the observed scale lengths with the photochemical lifetimes and velocities associated with the production of observed cometary CN by the photodissociation of HCN. The ratio of the intensity of the (0-1) band of CN at 4216 A to the (0-0) band at 3883 A has been determined from spectrograms of comet West, and is compared with theoretical values.