Binary and ternary recombination of H₂D⁺ and HD₂⁺ ions with electrons at 80 K

Abstract

The recombination of deuterated trihydrogen cations with electrons has been studied in afterglow plasmas containing mixtures of helium, argon, hydrogen and deuterium. By monitoring the fractional abundances of H3(+), H2D(+), HD2(+) and D3(+) as a function of the [D2]/[H2] ratio using infrared absorption observed in a cavity ring down absorption spectrometer (CRDS), it was possible to deduce effective recombination rate coefficients for H2D(+) and HD2(+) ions at a temperature of 80 K. From pressure dependences of the measured effective recombination rate coefficients the binary and the ternary recombination rate coefficients for both ions have been determined. The inferred binary and ternary recombination rate coefficients are: αbinH2D(80 K) = (7.1 ± 4.2) × 10(-8) cm(3) s(-1), αbinHD2(80 K) = (8.7 ± 2.5) × 10(-8) cm(3) s(-1), KH2D(80 K) = (1.1 ± 0.6) × 10(-25) cm(6) s(-1) and KHD2(80 K) = (1.5 ± 0.4) × 10(-25) cm(6) s(-1).

Stationary afterglow measurements of the temperature dependence of the electron–ion recombination rate coefficients of ${{\rm{H}}}_{2}{{\rm{D}}}^{+}$ and ${\mathrm{HD}}_{2}^{+}$ in He/Ar/H2/D2gas mixtures atT= 80–145 K

“…´-5 10 10 10 10 cm 17 14 14 14 3 . In agreement with our previous studies and with present experimental data we consider the following recombination processes with the indicated recombination rate coefficients: We assume, in agreement with experimental data, that the relative partial densities of ions (fractions) f H3 , f H2D , f HD2 and f D3 are constant during the plasma decay (see theexample of data in the middle panel figure 3 and also data in [37]).…”

“…1 ). Lower panel: The dependence of a effH2D and a effHD2 on [He] measured at 80 K. These recombination rate coefficients were evaluated using data from [37] with theaddition of several newly measured values of a S eff . The full and the open stars indicate the values of a effD3 obtained in the FALP [84] and SA-CRDS experiments [48], respectively.…”

“…The relative cross sections, the product branching ratios and the dependence of recombination on rotational excitation were studied by the Test Storage Ring (TSR) group in Heidelberg [35,36]. In beam experiments with + H 3 ions the rotational temperature of the ions was probably high and not well known, but in the case of HD 2 ions has not been studied previously in plasma afterglow experiments (with the exception of our recent study at 80 K [37]) because of the difficulty of producing plasmas that contain only a single ion species, either…”

Dissociative recombination of H3+and D5+

“…The most significant experimental progress since the last Royal Society Discussion Meeting is that there are now stationary afterglow results for these isotopologues from the Prague group [16]. This means that it is now possible to make a comparison of experimental results from ion storage rings and plasma afterglows [16], and from ab initio calculations [17].…”

“…It was pointed out in [5] that it is difficult to perform plasma afterglow experiments on H 2 D + and HD + 2 , and by that time (2010) only recombination of H + 3 and D + 3 had been studied in afterglow experiments. The most significant experimental progress since the last Royal Society Discussion Meeting is that there are now stationary afterglow results for these isotopologues from the Prague group [16]. This means that it is now possible to make a comparison of experimental results from ion storage rings and plasma afterglows [16], and from ab initio calculations [17].…”