Flowing afterglow studies of temperature dependencies for electron dissociative recombination of HCNH+, CH3CNH+ and CH3CH2CNH+ and their symmetrical proton-bound dimers
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, CH3 and C2H5) and their symmetrical proton-bound dimers (RCNH+NCR). The power law temperature dependencies of the recombination coefficients, alpha(e), over the temperature range 180 to 600K for the protonated ions are alpha(e)(T)(cm(3) s(-1))=3.5+/-0.5 x 10(-7) (300/T)(1.38) for HCNH+, alpha(e)(T)=3.4+/-0.5 x 10(-7) (300/T)(1.03) for CH3CNH+, and alpha(e)(T)=4.6+/-0.7 x 10(-7) (300/T)(0.81) for CH3CH2CNH+. The equivalent values for the proton-bound dinners are alpha(e)(T)(cm(3) s(-1))=2.4+/-0.4 x 10(-6)(300/T)(0.5) for (HCN)(2)H+ to alpha(e)(T)=2.8+/-0.4 x 10(-6)(300/T)(0.5) for (CH3CN)(2)H+, and alpha(e)(T)=2.3+/-0.3 x 10(-6)(300/T)(0.5) for (CH3CH2CN)(2)H+. The relevance of these data to molecular synthesis in the interstellar medium and the Titan ionosphere are discussed. (C) 2009 Elsevier Ltd. All rights reserved.