Abstract

The ortho-para conversion in solid hydrogen is investigated at 12, 4.2, and 1.57 K in long-term experiments up to 1200 h. The results are discussed in the light of the influence of molecular diffusion on the conversion rate. At 4.2 and 1.57 K, the conversion rate shows that the diffusion coefficient is $D\ensuremath{\approx}{10}^{\ensuremath{-}20}$ ${\mathrm{cm}}^{2}$ ${\mathrm{sec}}^{\ensuremath{-}1}$. This value is much larger than those predicted from an extrapolation of experimental results at higher temperatures and from recent theoretical predictions. At 1.57 K, an increase of the conversion rate with decreasing $o\ensuremath{-}{\mathrm{H}}_{2}$ concentration is observed. Calculations show this increase is due to clustering of $o\ensuremath{-}{\mathrm{H}}_{2}$ molecules caused by electric quadrupole-quadrupole interactions between them. The estimated diffusion rate is consistent with that found previously from the rate of clustering.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.