Experimental studies of the dissociative recombination of CD₃CDOD⁺ and CH₃CH₂OH

¹ Department of PhysicsStockholm University, 106 91 Stockholm, Sweden
e-mail: mh@physto.se
² Radboud University Nijmegen, Institute for Molecules and Materials, PO Box 9010, 6500 GL Nijmegen, The Netherlands
³ Institute of Physics, Jan Kochanowski University, Świȩtokrzyska 15, 25406 Kielce, Poland
⁴ Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Rd., Lanzhou 730000, PR China
⁵ Department of Physics, Albert-Ludwigs Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg Germany
⁶ Manne Siegbahn Laboratory, Frescativägen 26, 114 18 Stockholm, Sweden

Received: 12 April 2010
Accepted: 22 July 2010

Abstract

Aims. We determine branching fractions, cross sections and thermal rate constants for the dissociative recombination of CD₃CDOD⁺ and CH₃CH₂OH at the low relative kinetic energies encountered in the interstellar medium.

Methods. The experiments were carried out by merging an ion and electron beam at the heavy ion storage ring CRYRING, Stockholm, Sweden.

Results. Break-up of the CCO structure into three heavy fragments is not found for either of the ions. Instead the CCO structure is retained in 23  ±  3% of the DR reactions of CD₃CDOD⁺ and 7  ±  3% in the DR of CH₃CH₂OH, whereas rupture into two heavy fragments occurs in 77  ±  3% and 93  ±  3% of the DR events of the respective ions. The measured cross sections were fitted between 1–200 meV yielding the following thermal rate constants and cross-section dependencies on the relative kinetic energy: σ(E_cm [eV] ) = 1.7 ± 0.3 × 10^-15(E_cm [eV] ) ^{− 1.23 ± 0.02} cm² and k(T) = 1.9 ± 0.4 × 10^-6(T / 300) ^{− 0.73 ± 0.02} cm³ s^-1 for CH₃CH₂OH as well as k(T) = 1.1 ± 0.4 × 10^-6(T / 300) ^{− 0.74 ± 0.05} cm³ s^-1 and σ(E_cm [eV]) = 9.2 ± 4 × 10^-16(E_cm [eV] ) ^{− 1.24 ± 0.05} cm² for CD₃CDOD⁺