Contrast between the mechanisms for dissociative electron attachment to CH3SCN and CH3NCS

The kinetics of thermal electron attachment to methyl thiocyanate (CH3SCN), methyl isothiocyanate (CH3NCS), and ethyl thiocyanate (C2H5SCN) were measured using flowing afterglow-Langmuir probe apparatuses at temperatures between 300 and 1000 K. CH3SCN and C2H5SCN undergo inefficient dissociative attachment to yield primarily SCN− at 300 K (k = 2 × 10−10 cm3 s−1), with increasing efficiency as temperature increases. The increase is well described by activation energies of 0.17 eV (CH3SCN) and 0.14 eV (C2H5SCN). CN− product is formed at