Rapid Ortho-to-para Nuclear Spin Conversion of H₂ on a Silicate Dust Surface

The H2 molecule has two nuclear spin isomers, the so-called ortho and para isomers. Nuclear conversion (NSC) between these states is forbidden in gas phase. energy difference lowest as large 14.7 meV, corresponding to ~170 K. Therefore, each state of differently affects not only chemistry but also macroscopic dynamics space, thus, ortho-to-para abundance ratio (OPR) significant impacts on various astronomical phenomena. For a long time, OPR nascent upon formation dust grains been assumed have statistical value three gradually equilibrate phase at temperature circumstances. Recently, NSC was experimentally revealed occur water ice very low temperatures thus incorporated into gas-dust chemical models. However, molecules should form well before are coated by ice. Information about how behaves bare silicate ice-mantle lacking. Knowing influence if changes even surface within an astronomically meaningful time scale desirable. We report first laboratory measurements physisorbed amorphous (Mg2SiO4) up 18 found rapidly.