Abstract Molecular hydrogen exists in nuclear-spin isomers of ortho and para species according to the total nuclear spin. These species are correlated to the rotational states with even and odd rotational quantum numbers because of the symmetry of the total wavefunction with respect to the permutation of the two nuclei. Although interconversion between the ortho and para states is extremely slow in an isolated state, the conversion is promoted in a physisorption state via interaction with surfaces of not only magnetic but also diamagnetic materials. In a physisorption state, the rotational motion of hydrogen molecules is modified due to the potential anisotropy. The physisorption properties and interconversion rate of the ortho and para hydrogen have recently been investigated on well-defined surfaces, which allow detailed comparison with theory. Furthermore, relative abundance of the ortho and para hydrogen in astronomical circumstances has been reported in recent years, which often shows a value out of equilibrium with the environment temperature. Physisorption and ortho–para conversion on the surfaces of interstellar media are expected to enable deeper understanding of astronomical phenomena. In this article, we review recent progress of experimental and theoretical studies on the physisorption and ortho–para conversion of molecular hydrogen and its relevance to the recent astronomical observation.

中文翻译：

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固体表面分子氢的物理吸附和邻位转化

摘要 根据总核自旋，氢分子存在于邻位和对位物种的核自旋异构体中。由于总波函数相对于两个核的排列的对称性，这些物质与具有偶数和奇数旋转量子数的旋转状态相关。尽管在孤立状态下邻位和对位之间的相互转换非常缓慢，但通过与不仅磁性材料而且还与抗磁性材料的表面相互作用，在物理吸附状态下促进了这种转换。在物理吸附状态下，氢分子的旋转运动由于潜在的各向异性而改变。最近在明确定义的表面上研究了邻位和对位氢的物理吸附性质和相互转化率，这允许与理论进行详细比较。此外，近年来在天文环境中报道了邻位和对位氢的相对丰度，这通常显示出与环境温度不平衡的值。星际介质表面的物理吸附和正对转换有望使人们更深入地了解天文现象。在本文中，我们回顾了分子氢物理吸附和邻位转化的实验和理论研究的最新进展及其与近期天文观测的相关性。星际介质表面的物理吸附和正对转换有望使人们更深入地了解天文现象。在本文中，我们回顾了分子氢物理吸附和邻位转化的实验和理论研究的最新进展及其与近期天文观测的相关性。星际介质表面的物理吸附和正对转换有望使人们更深入地了解天文现象。在本文中，我们回顾了分子氢物理吸附和邻位转化的实验和理论研究的最新进展及其与近期天文观测的相关性。