Dissociative recombination study of at CRYRING: absolute cross-section, chemical branching ratios and three-body fragmentation dynamics

Abstract

The paper reports an investigation of the dissociative recombination of PD þ 2 at the heavy-ion storage ring CRYRING. The absolute cross-section has been measured as a function of centre-of-mass energy ranging from 1 meV to 0.1 eV. The experiment performed has shown the dissociative recombination of PD þ 2 to be dominated by three-body break-up, with a branching ratio of about 78%. Competition between the available three-body channels producing the ground state, P( 4 S), and the first two excited states, P( 2 D) and P( 2 P), is observed. The formation of the first excited state dominates over the other two almost equally probable channels with about 75% of all three-body events. The results indicate that the kinetic energy released in the three-body break-up of PD þ 2 is randomly shared between the deuterium atoms. The intra-molecular angle on dissociation has also been investigated. A comparative analysis of the dissociative recombination dynamics for the two isovalent systems, PD þ 2 and NH þ 2 , is undertaken.

Three-Body Breakup in the Dissociative Recombination of the Covalent Triatomic Molecular IonO3+

“…The ID has been used for such purpose. Since the ID was operated only as a twodimensional position-sensitive detector, only the transverse separations between the fragments are possible to record [26]. The molecular plane upon dissociation is randomly oriented with the respect to the plane of the ID, which leads to a broad distribution of the apparent KER in the detector plane.…”

Dissociative recombination of CH5+and CD5+:

“…However, the resolution of the detector does not allow a detailed investigation of these states. It is noted that so far it has only been feasible to resolve contributions from the electronic states [35,39,41,49,52] although, quite recently, it has been demonstrated for the OH(v = 0-2) states arising from the DR of H 3 O + [53]. In order to estimate the reaction energy distribution, MCS-generated T D distributions for E k values ranging from 0.15 to 3.35 eV with a step of 0.4 eV (Fig.…”

“…The data with T D > 20 mm were also analyzed via a parameter ρ which describes the ratio between hydrogen atom energies, that is, ρ = (d cm−H 1 /d cm−H 2 ) 2 [35,39,41,49]. The experimental and the Monte Carlo simulated distributions are shown in Fig.…”

“…Semaniak et al [18] reported the dominance of the three-body channel CH 3 + H + H (≈70%, CRYRING), while the group of Adams and co-workers observed that the CH 4 + H channel dominates (≈95%, FALP) [26]. Furthermore, as with the DR of CH 5 + [18], in many storage ring studies on the DR of small polyatomic, hydrogen-and deuterium-rich ions, three-body fragmentation has been observed as the dominant product channel at ≈60%-80% of the reaction flux [13,14,[27][28][29][30][31][32][33][34][35][36][37][38].…”

Rotational state effect and fragmentation of small polyatomic molecular ions

“…Moreover, observation of four-body break-up was reported, though it was not a dominant channel [12]. A systematic investigation into the fragmentation of XH 2 + ions (X=H, C, N, O and P) has revealed a propensity for the three-body break-up [13][14][15][16][17]. To shed more light on the DR fragmentation of XH …”