Titan's atmospheric haze: the case for HCN incorporation

It is suggested that the incorporation of HCN in Titan's atmospheric haze may be an important process affecting the HCN profile and the C/N ratio in Titan's haze. By introducing a loss to the haze term for HCN (i.e, a production term of "poly-HCN") in the photochemical model of Lara et al. (1996), we have improved the model's ability to simultaneously reproduce the observed HCN and Ca hydrocarbon profiles in Titan's lower stratosphere. The loss rate of HCN by this process may be a few times 10(8) cm(-2) s(-1). The calculated C/N ratio in the haze, assuming that the haze is primarily produced from C6H2, C8H2 and "poly-HCN", is approximately equal to 2, in agreement with the composition of laboratory tholin analogues.