Extended Data Table 2 Reaction rates used herein
From: Astrophysical detection of the helium hydride ion HeH+
- (1) The rate coefficient (in cm3 s−1) was obtained by averaging the published cross-sections25 over a Maxwell–Boltzmann distribution, and applies to temperatures in the range 5,000 K to 20,000 K. The published cross-sections are for collisions in which He+ (1s) and H (1s) are in the singlet state (total spin 0), but as only one-quarter of collisions will have spin 0, the rate has been reduced by a factor of four. Values in the literature13,36,37 vary widely. (2) This value corrects an error in the computation27 of the thermal rate coefficient from the cross-section measurements. Taking as valid the primary data of ref. 27, namely, the merged-beam cross-sections given in their figure 3, the thermal rate coefficients was recomputed by applying the methods developed;, for example, for the calculation of the dissociative recombination cross-section of HCl+ (ref. 26); we find the thermal rate coefficient to be an order of magnitude below that originally computed27. (3) Ref. 35 shows the rate coefficient obtained from quantum calculations.
