Binary and ternary recombination of and ions with electrons in low temperature plasma

Binary recombination of para- and ortho-H 3 + with electrons at low temperatures

“…This resulted in a convergence with experimental DR data reported from ion storage rings where experimentalists had realized the impact of rotational excitation of the H + 3 ions on the DR reaction rate, especially with respect to the importance of the DR process in interstellar molecular clouds [11][12][13]. Final convergence between theory and the remaining important experimental techniques, stationary and flowing afterglow, was reached after recognizing that a fast third-body reaction, not previously considered, stabilizes the recombination process in such plasmas [4,14,15]. However, recently it has been shown [16,17] that the assumption of rotationally cold H + 3 ions in storage rings was not entirely correct [17].…”

“…A mixture of He/Ar/H 2 with a typical composition 10 17 /10 14 /10 14 cm −3 flows continuously along the discharge tube. Details of the ion formation reactions are given elsewhere [4,5,27]. 'A parahydrogen generator' prepares samples of para-enriched H 2 ( e H 2 ) [26].…”

“…The discrepancies between measurements of the binary dissociative reaction rate and the theoretical complexity of this seemingly simple reaction led to a great deal of fruitful research on this process. The history of H + 3 recombination studies has been adequately covered in several review articles [3][4][5][6][7][8][9]. Recently, both theory and experiment have converged to a value for the rate of this particular reaction.…”

“…The measured values of p a bin , o a bin , n a bin and values of n a bin from previous FALP experiments [4,14,15] are plotted in figure 3. The displayed errors of rate coefficients are 1s errors, and systematic errors (mainly from determination of ion number densities) were estimated to be less than 10 per cent.…”

“…To obtain a eff from the measured electron density decay curves, we used direct fits to the data and, in addition, the more advanced 'integral analysis' technique [31]. We deliberately excluded the first 50-150 ms of the afterglow decay from the data analysis because some new ions were probably still being formed (for details see [4,20,26,31]). The observed dependences of n a eff and e a eff on [He] at 140 K are shown in figure 2a.…”