title: Dissociative recombination of CH4(+).
abstract: CH4(+) is an important molecular ion in the astrochemistry of diffuse clouds, dense clouds, cometary comae, and planetary ionospheres. However, the rate of one of the common destruction mechanisms for molecular ions in these regions, dissociative recombination (DR), is somewhat uncertain. Here, we present absolute measurements for the DR of CH4(+) made using the heavy ion storage ring CRYRING in Stockholm, Sweden. From our collision-energy dependent cross-sections, we infer a thermal rate constant of k(Te) = 1.71(±0.02) × 10(–6)(Te/300)(−0.66(±0.02)) cm3 s(–1) over the region of electron temperatures 10 ≤ Te ≤ 1000 K. At low collision energies, we have measured the branching fractions of the DR products to be CH4 (0.00 ± 0.00); CH3 + H (0.18 ± 0.03); CH2 + 2H (0.51 ± 0.03); CH2 + H2 (0.06 ± 0.01); CH + H2 + H (0.23 ± 0.01); and CH + 2H2 (0.02 ± 0.01), indicating that two or more C–H bonds are broken in 80% of all collisions.
authors: Department of Physics, Stockholm University , Albanova University Center, SE-106 91 Stockholm, Sweden.
authors: Richard D
authors: RD
authors: Thomas
authors: Iryna
authors: I
authors: Kashperka
authors: E
authors: E
authors: Vigren
authors: Wolf D
authors: WD
authors: Geppert
authors: Mathias
authors: M
authors: Hamberg
authors: Mats
authors: M
authors: Larsson
authors: Magnus
authors: M
authors: af Ugglas
authors: Vitali
authors: V
authors: Zhaunerchyk