State-to-state predissociation dynamics of hydroxyl radical via the A2Σ+ state

G Sun, W Zhou, X Zheng, Y Qin, Y Song, Y Yuan… - Molecular …, 2021 - Taylor & Francis
G Sun, W Zhou, X Zheng, Y Qin, Y Song, Y Yuan, J Zhang
Molecular Physics, 2021Taylor & Francis
Photo-predissociation dynamics of jet-cooled hydroxyl radical (OH) via several rovibrational
levels (v′= 2–4, N′= 0–2, J′= 0.5–2.5, F 1) in the A2Σ+ state are studied using the high–n
Rydberg-atom time-of-flight (HRTOF) technique. Spin–orbit branching fractions and angular
distributions of the H (2S)+ O (3PJ= 2, 1, 0) product channels are measured in the product
translational energy distributions. The A2Σ+ v′= 2 and 3 states of OH predissociate
predominantly via the single 14Σ− repulsive state, while the A2Σ+ v′= 4 state …
Abstract
Photo-predissociation dynamics of jet-cooled hydroxyl radical (OH) via several rovibrational levels (v′ = 2–4, N′ = 0–2, J′ = 0.5–2.5, F1) in the A2Σ+ state are studied using the high–n Rydberg-atom time-of-flight (HRTOF) technique. Spin–orbit branching fractions and angular distributions of the H(2S) + O(3PJ = 2,1,0) product channels are measured in the product translational energy distributions. The A2Σ+ v′ = 2 and 3 states of OH predissociate predominantly via the single 14Σ repulsive state, while the A2Σ+ v′ = 4 state predissociates via the 14Σ, 12Σ, and 14Π repulsive states and quantum interferences among these dissociation pathways play an important role in the O(3PJ = 2,1,0) product fine-structure state distribution. The experimental O(3PJ) product spin–orbit branching ratios are in excellent agreement with the full quantum multichannel scattering calculations that include all the interactions in the crossing region, recoupling zone, and asymptotic zone [Parlant and Yarkony, J. Chem. Phys. 110, 363 (1999)]. The product angular distributions strongly depend on the rotational transitions and rotational levels in the A2Σ+ state. The measured anisotropy parameters are in reasonable agreement with predictions from the simulation programme (Betaofnu) [Kim et al., J. Chem. Phys. 125, 133316 (2006)], using dissociation lifetime, excitation frequency, rotational level, and rotational constant. The predissociation time scales of OH A2Σ+ are determined to be 130 ± 30 ns and ≥ 14 ± 3 ps for the v′ = 2, N′ = 2, J′ = 2.5 and v′ = 4, N′ = 0, J′ = 0.5 levels, respectively.
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