Hazra Saikat, Naskar Koushik, Adhikari Satrajit, Varandas António J C
School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
School of Physics and Physical Engineering, Qufu Normal University, Qufu 273165, P. R. China.
J Phys Chem A. 2024 Oct 17;128(41):8833-8844. doi: 10.1021/acs.jpca.4c02243. Epub 2024 Oct 8.
The collision-induced rate coefficients of ortho-para conversion for the H + H reaction provide accurate information to probe the lifetime of cold environments in interstellar media. Rotationally resolved reaction probabilities are calculated at the low collision energy regime (0 < ≤ 0.3 eV) by employing the coupled three-dimensional (3D) time-dependent wave packet (TDWP) formalism in hyperspherical coordinates on a recently constructed ab initio ground adiabatic potential energy surface of H [ , , 204306] for the process H + H ( = 0, = 0-5) → H + H (' = 0, '). Cross-sections are then computed from the converged reaction probabilities as a function of total angular momentum () over the same energy regime and subsequently employed to obtain the rate constants for the ortho-to-para (O-P) and para-to-ortho (P-O) conversions and their ratio. The ratio of ortho-para conversion shows (a) appropriate convergence with the inclusion of a higher number of initial rotational states as well as a reasonable agreement with the results from a quantum statistical method and (b) a peak at lower temperature that could be due to the available collision energy for transitions involving lower rotational states ( = 0 → ' = 1).
H + H反应的邻-对转换的碰撞诱导速率系数为探测星际介质中冷环境的寿命提供了准确信息。通过在超球坐标中采用耦合三维（3D）含时波包（TDWP）形式，在低碰撞能区（0 < ≤ 0.3 eV），利用最近构建的H [,, 204306]的从头算基态绝热势能面，计算了H + H（ = 0, = 0 - 5）→ H + H（' = 0, '）过程的转动分辨反应概率。然后在相同能量范围内，根据收敛的反应概率计算作为总角动量（）函数的截面，并随后用于获得邻-对（O - P）和对-邻（P - O）转换的速率常数及其比值。邻-对转换的比值显示：（a）随着包含更多初始转动状态而有适当收敛，并且与量子统计方法的结果有合理的一致性；（b）在较低温度下有一个峰值，这可能是由于涉及较低转动状态（ = 0 → ' = 1）跃迁的可用碰撞能量所致。
