Effects of a shock on the molecular composition of a diffuse interstellar cloud

Postshock abundances have been followed for 105 years after the passage of a 10 km s-1 shock through a gas of initial density 100 cm-3. Abundance profiles and postshock column densities are presented for species which show marked changes in abundance, namely for C, C+, CO, CO2, O2, H2CO, CH3, CH4, C2H, C2H2, O, OH, H2O, CH+, CH+2, CH+/sub 3,/ CO+, HCO+, N2, NO, CN, HCN, NH, NH2, NH3, HS, H2S, SO, SO2, CS, and H2CS. Formation and destruction mechanisms for these species are discussed. We suggest that the enhancement of HCO+ in the shocked gas of IC 443 may be due to the presence of an appreciable abundance of C+ in the preshocked cloud