Experimental studies of the dissociative recombination processes for the dimethyl ether ions CD₃OCD and (CD₃)₂OD⁺

¹ Department of Physics, Stockholm University, Alba Nova, 106 91 Stockholm, Sweden e-mail: mh@physto.se
² Institute of Physics, Jan Kochanowski University, Świętokrzyska 15, 25406 Kielce, Poland
³ Manne Siegbahn Laboratory, Frescativägen 26, 114 18 Stockholm, Sweden

Received: 16 December 2009
Accepted: 4 February 2010

Abstract

Aims. Determination of branching fractions, cross sections and thermal rate coefficients for the dissociative recombination of CD₃OCD₂⁺ (0–0.3 eV) and (CD₃)₂OD⁺ (0–0.2 eV) at the low relative kinetic energies encountered in the interstellar medium.

Methods. The measurements were carried out using merged electron and ion beams at the CRYRING storage ring, Stockholm, Sweden.

Results. For (CD₃)₂OD⁺ we have experimentally determined the branching fraction for ejection of a single hydrogen atom in the DR process to be maximally 7% whereas 49% of the reactions involve the break up of the COC chain into two heavy fragments and 44% ruptures both C–O bonds. The DR of CD₃OCD₂⁺ is dominated by fragmentation of the COC chain into two heavy fragments. The measured thermal rate constants and cross sections are k(T) = 1.7±0.5 × 10^-6(T/300)  cm³ s^-1, σ = 1.2±0.4 × 10^-15(E_cm[eV]) cm² and k(T) = 1.7±0.6 × 10^-6(T/300) cm³ s^-1, σ = 1.7±0.6 × 10^-15(E_cm[eV]) cm² for CD₃OCD₂⁺ and (CD₃)₂OD⁺, respectively.