Institute for Molecules and Materials, Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
Tomsk State University, Ave. Lenin, 36, 634050 Tomsk, Russia and Institute of Spectroscopy, Russian Academy of Sciences, Fizicheskaya St. 5, 108840 Troitsk, Moscow, Russia.
J Chem Phys. 2018 Sep 28;149(12):121101. doi: 10.1063/1.5051610.
Molecular oxygen (O) is predicted to be a major reservoir of elemental oxygen in dense interstellar molecular clouds. However, the abundance of O derived from astronomical observations is much lower than expected. Solving the discrepancies between models and observations requires a review of the chemistry and collisional excitation of O in space. In particular, O-H collisions are crucial to derive O abundance in space from the interstellar spectra. A crossed molecular beam experiment to probe the rotational excitation of O due to H collisions at energies of 650 cm is reported. Velocity map imaging was combined with state-selective detection of O( ) by (2 + 1) resonance-enhanced multiphoton ionization. The obtained raw images were corrected from density to flux and the differential cross sections (DCSs) were then extracted. Exact quantum mechanical calculations were also performed. Very good agreement between experimental and theoretical DCSs was found. The agreement demonstrates our ability to determine inelastic processes between O molecules and H both theoretically and experimentally and that the excitation of O in the interstellar medium can be correctly modeled. Consequences on the astrophysical modeling are briefly evaluated.
分子氧 (O) 预计是致密星际分子云中元素氧的主要储库。然而，天文学观测到的 O 丰度远低于预期。要解决模型和观测之间的差异，需要对 O 在太空中的化学和碰撞激发进行审查。特别是，O-H 碰撞对于从星际光谱中得出太空中的 O 丰度至关重要。报告了一项能量为 650 cm 的 H 碰撞导致 O 旋转激发的交叉分子束实验。速度图成像与 O( )的态选择性检测相结合，通过 (2 + 1) 共振增强多光子电离。从密度到通量校正了获得的原始 图像，然后提取了微分截面 (DCS)。还进行了精确的量子力学计算。实验和理论 DCS 之间非常吻合。这种一致性表明我们有能力从理论和实验上确定 O 分子和 H 之间的非弹性过程，并且可以正确地模拟星际介质中 O 的激发。简要评估了对天体物理模型的影响。
