Highly selective cryogenic reactions in solid hydrogen on pseudo cosmic dust surface

作为低温暗星云中生物分子生长的宇宙尘埃模型，用硅胶与固体对氢的混合物在4.2K下阻止了H原子和其他自由基的反应，发现即使H原子在固体对氢中扩散，H原子和甲基自由基也不会在固体对氢中发生反应。氢原子也不与吸附在硅胶上的TEMPO自由基反应。H原子只能通过抽氢反应的隧道反应才能在固体仲氢中扩散。甲基自由基或硅胶等溶质分子会扭曲固体对氢的晶格结构，使氢原子的隧穿扩散变得困难。这可能是这样的自由基-自由基反应不能在4.2K下发生的主要原因。

As a model of cosmic dust for bio-molecular growth in dark nebula at cryogenic temperature, a mixture of silica gel with solid parahydrogen was used for deterring the reactions of H atoms and other radicals at 4.2 K. We found that H atoms and methyl radicals never react in solid parahydrogen even though H atoms were diffused in solid parahydrogen. H atoms also did not react with TEMPO radicals adsorbed on the silica gels. H atoms can diffuse in solid parahydrogen only by tunneling reaction of H abstraction reaction. Solute molecules as methyl radicals or silica gels may distort the lattice structure of solid parahydrogen, to make difficult for diffusion of H atoms by the tunneling. This can be the main reason why such radical-radical reactions could not take place at 4.2 K.