Experimental studies of the dissociative recombination processes for the dimethyl ether ions CD₃OCD$_{2}^{+}$ and (CD₃)₂OD⁺

Abstract

<i>Aims. <i/>Determination of branching fractions, cross sections and thermal rate coefficients for the dissociative recombination of CD<sub>3<sub/>OCD<sub>2<sub/><sup>+<sup/> (0–0.3 eV) and (CD<sub>3<sub/>)<sub>2<sub/>OD<sup>+<sup/> (0–0.2 eV) at the low relative kinetic energies encountered in the interstellar medium.<i>Methods. <i/>The measurements were carried out using merged electron and ion beams at the CRYRING storage ring, Stockholm, Sweden.<i>Results. <i/>For (CD<sub>3<sub/>)<sub>2<sub/>OD<sup>+<sup/> 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 CD<sub>3<sub/>OCD<sub>2<sub/><sup>+<sup/> is dominated by fragmentation of the COC chain into two heavy fragments. The measured thermal rate constants and cross sections are <i>k<i/>(<i>T<i/>) = 1.7<i>±<i/>0.5 × 10<sup>-6<sup/>(<i>T<i/>/300) cm<sup>3<sup/> s<sup>-1<sup/>, <i>σ<i/> = 1.2<i>±<i/>0.4 × 10<sup>-15<sup/>(<i>E<i/><sub>cm<sub/>[eV]) cm<sup>2<sup/> and <i>k<i/>(<i>T<i/>) = 1.7<i>±<i/>0.6 × 10<sup>-6<sup/>(<i>T<i/>/300) cm<sup>3<sup/> s<sup>-1<sup/>, <i>σ<i/> = 1.7<i>±<i/>0.6 × 10<sup>-15<sup/>(<i>E<i/><sub>cm<sub/>[eV]) cm<sup>2<sup/> for CD<sub>3<sub/>OCD<sub>2<sub/><sup>+<sup/> and (CD<sub>3<sub/>)<sub>2<sub/>OD<sup>+<sup/>, respectively.