Flowing afterglow studies of temperature dependencies for electron dissociative recombination of HCNH +, CH 3CNH + and CH 3CH 2CNH + and their symmetrical proton-bound dimers

Abstract

A study has been made using a variable temperature flowing afterglow Langmuir probe technique (VT-FALP) to determine the equilibrium temperature dependencies of the dissociative electron-ion recombination of the protonated cyanide ions (RCNH +, where R=H, CH 3 and C 2H 5) and their symmetrical proton-bound dimers (RCNH +NCR). The power law temperature dependencies of the recombination coefficients, α e, over the temperature range 180 to 600 K for the protonated ions are α e( T)(cm 3 s −1)=3.5±0.5×10 −7 (300/ T) 1.38 for HCNH +, α e( T)=3.4±0.5×10 −7 (300/ T) 1.03 for CH 3CNH +, and α e( T)=4.6±0.7×10 −7 (300/ T) 0.81 for CH 3CH 2CNH +. The equivalent values for the proton-bound dimers are α e( T)(cm 3 s −1)=2.4±0.4×10 −6(300/ T) 0.5 for (HCN) 2H + to α e( T)=2.8±0.4×10 −6(300/ T) 0.5 for (CH 3CN) 2H +, and α e( T)=2.3±0.3×10 −6(300/ T) 0.5 for (CH 3CH 2CN) 2H +. The relevance of these data to molecular synthesis in the interstellar medium and the Titan ionosphere are discussed.