Probing the resonance potential in the F atom reaction with hydrogen deuteride with spectroscopic accuracy

Abstract

Reaction resonances are transiently trapped quantum states along the reaction coordinate in the transition state region of a chemical reaction that could have profound effects on the dynamics of the reaction. Obtaining an accurate reaction potential that holds these reaction resonance states and eventually modeling quantitatively the reaction resonance dynamics is still a great challenge. Up to now, the only viable way to obtain a resonance potential is through high-level ab initio calculations. Through highly accurate crossed-beam reactive scattering studies on isotope-substituted reactions, the accuracy of the resonance potential could be rigorously tested. Here we report a combined experimental and theoretical study on the resonance-mediated F + HD --> HF + D reaction at the full quantum state resolved level, to probe the resonance potential in this benchmark system. The experimental result shows that isotope substitution has a dramatic effect on the resonance picture of this important system. Theoretical analyses suggest that the full-dimensional FH(2) ground potential surface, which was believed to be accurate in describing the resonance picture of the F + H(2) reaction, is found to be insufficiently accurate in predicting quantitatively the resonance picture for the F + HD --> HF + D reaction. We constructed a global potential energy surface by using the CCSD(T) method that could predict the correct resonance peak positions as well as the dynamics for both F + H(2) --> HF + H and F + HD --> HF + D, providing an accurate resonance potential for this benchmark system with spectroscopic accuracy.

Probing Quantum Dynamics of Elementary Chemical Reactions via Accurate Potential Energy Surfaces

“…More remarkably, the theoretical results obtained on the FXZ-PES can reproduce very well the dramatic variations in experimental DCS shown in Fig. 10, as well as the observed intriguing trimodal structures in the HF(v = 2) rotational distribution [67].…”

“…The XXZ (Xu-Xie-Zhang) potential energy surface (XXZ-PES) was constructed for the F(P 3/2 ) + H 2 reaction, using the internally contracted multi-reference configuration interaction method [63,64] with the Davidson correction (icMRCI+Q) [65] with the augmented correlation-consistent valence 5-zeta (aug-ccpv5z) basis set of Dunning [66]. In order to interpret the F + HD experimental result, which will be discussed later in this article, the FXZ (Fu-Xu-Zhang) potential energy surface (FXZ-PES) for this system was also constructed [67] based upon the spin unrestricted, coupled cluster method, including single and double excitations with perturbative treatment of triple excitations, using the same basis set for the XXZ-PES. The spin-orbit effect was also included in both surfaces.…”

“…In Ref. [67], the scattering signal at the backward scattering direction for HF(v = 2) was also measured in the collision energy range between 0.2 and 1.2 kcal/mol. Figure 11 shows the summed signal of HF(v = 2, j = 0 to 3) as a function of collision energy, with a peak around 0.39 kcal/mol.…”

“…High resolution crossed beam scattering experiments were carried out for this reaction using the D-atom Rydberg tagging TOF method [67]. Full ro-vibrational state (HF) resolved differential cross sections for this reaction were measured in the collision energy range from 0.3 to 1.2 kcal/mol.…”

Shape resonance in the H + D2O → D + HOD reaction: a full-dimensional quantum dynamics study

“…Since the first theoretical prediction of reaction resonances in the F + H 2 reaction in the early 1970s, 9-11 the search for evidence of such resonances in this reaction has attracted much attention from many top research groups in this field. [12][13][14][15][16][17][18][19][20] Recently, the F + H 2 (HD) reaction was studied extensively in an effort to understand the dynamical resonances in this important system, 8,[21][22][23] using the high-resolution crossed molecular beams technique in combination with full quantum scattering calculation based on accurate potential energy surfaces. The advances made in these studies have provided a clear physical picture of dynamical resonances in this benchmark system that has eluded us for decades.…”