Pressure-enhanced ortho-para conversion in solid hydrogen up to 58 GPa.

Eggert, J H; Karmon, E; Hemley, R J; Mao, A; Goncharov, A F · Proc Natl Acad Sci U S A · 1999

basic_science · Level V

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Abstract

We measured the ortho-para conversion rate in solid hydrogen by using Raman scattering in a diamond-anvil cell, extending previous measurements by a factor of 60 in pressure. We confirm previous experiments that suggested a decrease in the conversion rate above about 0.5 GPa. We observe a distinct minimum at 3 GPa followed by a drastic increase in the conversion rate to our maximum pressure of 58 GPa. This pressure enhancement of conversion is not predicted by previous theoretical treatments and must be due to a new conversion pathway.