Merged electron-ion beam experiments. IV. Dissociative recombination for the methane group CH⁺,...,CH₅⁺

Dissociative recombination of the methane family ions: rate coefficients and implications

“…A multipass study of the DR of CH þ 3 (Vejby-Christensen et al, 1997) performed at the ASTRID storage ring in Denmark produced energy dependent cross-sections that were qualitatively similar (see Fig. 3 in Vejby-Christensen et al, 1997) to the original MEIBE (Mul et al, 1981) cross-sections. Because of a weak ion beam current however, their multipass study was only able to determine relative cross-sections.…”

“…The first multipass study of the DR of CH þ was performed at the TSR storage ring facility at the Max Planck Institute (Amitay et al, 1996). While they did not calculate a temperature dependent rate coefficient, the fact that their energy dependent cross-sections were systematically lower than the original MEIBE results (Mul et al, 1981) by a factor of 2 (see Figs. 8 and 9 in Amitay et al, 1996) allows us to estimate a rate of 1.0 Â 10 À7 (T e /300) À0:37 cm 3 /s for their storage ring experiment.…”

“…Because of a weak ion beam current however, their multipass study was only able to determine relative cross-sections. Their relative cross-sections were then normalized at 0.1 eV to the data of Mul et al (1981) to obtain absolute crosssections (Vejby-Christensen et al, 1997). As a result, the multipass and single pass results for this species appear to be in excellent agreement.…”

“…These experiments were originally performed as part of an extensive review of the MEIBE apparatus and procedures (Sheehan, 2000). The goal was to repeat original MEIBE experiments, such as with the methane family ions (Mul et al, 1981), in the hopes of shedding light on the apparent discrepancies between the recombination rates reported by different research groups. In each case, the new MEIBE rates were in good agreement with the original values.…”

(New) molecular ions in the interstellar medium

“…The DR reaction rate of CH + 3 is moderate [27] and has been revisited recently [28] at the heavy storage ring CRYRING. We expect that the corresponding value for CH 2 D + is similar but a dedicated study would be important.…”