Oscillator strengths for lines of the (0,0) and (1,0) bands of the C 1Pi--X 1Σ+ system of HCl and the abundance of HCl in diffuse interstellar clouds

Oscillator strengths (f-values) for twenty lines of the (0, 0) band and one line of the (1, 0) band of the C 1Pi--X 1Σ+ system of HCl have been measured using quantitative photographic techniques. The f-value for the R(0) line of the (0, 0) band at 129.0257 nm, which is the stronger of the two lines that have been searched for but not detected in diffuse interstellar clouds, is 0.185 +- 0.037. This value and the observations of absorption by chlorine species in the zeta Oph cloud have been used to reassess aspects of the chemical models of diffuse clouds