Dissociative recombination of protonated methanol

The branching ratios of the different reaction pathways and the overall rate coefficients of the dissociative recombination reactions of CH(3)OH(2)(+) and CD(3)OD(2)(+) have been measured at the CRYRING storage ring located in Stockholm, Sweden. Analysis of the data yielded the result that formation of methanol or deuterated methanol accounted for only 3 and 6% of the total rate in CH(3)OH(2)(+) and CD(3)OD(2)(+), respectively. Dissociative recombination of both isotopomeres mainly involves fragmentation of the C - O bond, the major process being the three-body break-up forming CH(3), OH and H (CD(3), OD and D). The overall cross sections are best fitted by sigma = 1.2 +/- 0.1 x 10(-15) E(-1.15 +/- 0.02) cm(2) and sigma = 9.6 +/- 0.9 x 10(-16) E(-1.20 +/- 0.02) cm(2) for CH(3)OH(2)(+) and CD(3)OD(2)(+), respectively. From these values thermal reaction rate coefficients of k(T) = 8.9 +/- 0.9 x 10(-7) (T/300) (- 0.59 +/- 0.02) cm(3) s(-1) (CH(3)OH(2)(+)) and k( T) = 9.1 +/- 0.9 x 10(-7) (T/ 300) (- 0.63 +/- 0.02) cm(3) s(-1)(CD(3)OD(2)(+)) can be calculated. A non-negligible formation of interstellar methanol by the previously proposed mechanism via radiative association of CH(3)(+) and H(2)O and subsequent dissociative recombination of the resulting CH(3)OH(2)(+) ion to yield methanol and hydrogen atoms is therefore very unlikely.