| Issue |
Europhys. Lett.
Volume 52, Number 5, December I 2000
|
|
|---|---|---|
| Page(s) | 564 - 570 | |
| Section | Condensed matter: structure, mechanical and thermal properties | |
| DOI | https://doi.org/10.1209/epl/i2000-00474-0 | |
| Published online | 01 September 2002 | |
Measurement of the ortho-to-para hydrogen conversion
in the high-pressure compound 
1
Dipartimento di Fisica dell'Università - largo Enrico Fermi 2, I-50125
Firenze and INFM, Unità di Firenze - Italy
2
Istituto di Elettronica Quantistica, CNR - via Panciatichi 56/30 I-50127 Firenze
and INFM, Unità di Firenze - Italy
3
Laboratorio Europeo di Spettroscopie Non Lineari (LENS ), Firenze - Italy
Corresponding authors: grazzi@fi.infn.it ulivi@ieq.fi.cnr.it
Received:
2
August
2000
Accepted:
26
September
2000
Ortho-para hydrogen conversion kinetics has been measured in the stoichiometric Ar(H2)2 compound, at pressures from 3 to 35 GPa, by analysing the intensity of the rotational Raman transitions. The validity of this method to measure ortho-para composition for high-pressure solids is discussed, and verified for the pressures used in this work. The conversion rate increases with pressure of almost a factor of 50 in the investigated pressure range, but always remains lower than that measured for pure solid hydrogen at the same pressure. The different crystal structure, in particular the lower number of nearest neighbours, plays a significant role in this difference.
PACS: 62.50.+p – High-pressure and shock-wave effects in solids and liquids / 78.30.-j – Infrared and Raman spectra / 67.40.Fd – Dynamics of relaxation phenomena
© EDP Sciences, 2000
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