Dynamics of Three-Body Breakup in Dissociative Recombination:H2O+

Abstract

To better understand the propensity for the three-body breakup in dissociative recombination (DR) of dihydrides ( H(3)(+), NH(2)(+), CH(2)(+), and H(2)O(+)), we undertook a study of the dynamics of this process. A study of DR of H(2)O(+) to give O + H + H was carried out at the CRYRING Heavy-Ion Storage Ring in Stockholm. With the stored beam energy of 4.5 MeV, we separated the O signal from the H signals with a differential absorber, thus reducing the problem to a sum of two two-body problems. Results included (1) the ratio of O((3)P) to O((1)D) product, (2) the distribution of recoil-kinetic energy between the two hydrogen atoms, (3) the angular distribution between the hydrogen atoms in the O((3)P) channel and in the O((1)D) channel.

Electron energy-dependent product state distributions in the dissociative recombination of O2+

“…12 The branching fractions and quantum yields do not entirely agree with earlier measurements from our group that were taken at energies between 0 and 40 meV in a cold ion beam, 11 nor with the measurements performed at ASTRID by Kella et al ͑at 0 eV͒. 17 The latter experiment, however, involved the vibrationally excited mixed-isotope 16 …”

“…The difference in the arrival time of the two O atoms in each reaction is on the order of nanosecond and difficult to measure. 11,16 The effects of the 2D projection along with the length of the electron cooler are taken into account in the model for the distance distributions, which is extensively described elsewhere. 17,18 The toroidal region, i.e., the region where the electron beam merges into and demerges out of the ion beam, provides a collision region in which the electron collision energy is much larger than in the remainder of the electron cooler.…”

Vibrationally resolved rate coefficients and branching fractions in the dissociative recombination of O2+

“…The vibrational population in the parent ions can be observed directly. However, in the DR experiment the high beam energy means that extracting the arrival-time difference ͑ns͒ is nontrivial 13,42 and so only the positions of the fragments were recorded. The acquired data is therefore a 2D projection of the dissociation which, together with the long interaction region, limits the experimental energy resolution.…”

Three-body Reaction Dynamics in Dissociative Recombination

“…Manipulation of these parameters, while simulating the same "measurements" as were done in the laboratory, enables a detailed comparison to be made between the initial/final conditions in the simulation and the experimental observations. For example, Figure 5 shows the branching between the available channels for H 2 allowed information and insight to be obtained on the DR processes. The branching ratios between the competing three-body fragmentation channels for each of the XH ¥ 2 systems studied is given in Table 1 For the angular …”

“…See [8,9]) in a triple-coincidence experiment, monitoring the position and arrival time of the fragments from the DR reaction enables differentiation between the competing channels. Further to the standard detector arrangement, used in the D ¥ (D 2 O) 2 study, a new technique was employed for the XH ¥ 2 systems which enabled the heavier, X, atom to be identified [2,4]. In identifying the heavier atom, the centre of mass (c.m.)…”