Pressure-enhanced ortho-para conversion in solid hydrogen up to 58 GPa
J H Eggert1, E Karmon, R J Hemley
1Department of Physics, Colorado School of Mines, Golden, CO 80401, USA.
The ortho-para conversion rate in solid hydrogen was measured up to 58 GPa. A surprising increase in conversion rate at high pressures suggests a new pathway for this quantum phenomenon.
Area of Science:
- Condensed Matter Physics
- Quantum Chemistry
- Materials Science under extreme conditions
Background:
- The ortho-para conversion in solid hydrogen is a fundamental quantum mechanical process.
- Previous studies indicated a decrease in conversion rate above 0.5 GPa.
Purpose of the Study:
- To investigate the ortho-para conversion rate in solid hydrogen at unprecedented high pressures.
- To explore the pressure dependence of this quantum conversion phenomenon.
Main Methods:
- Raman scattering spectroscopy was employed.
- Measurements were conducted using a diamond-anvil cell to achieve high pressures up to 58 GPa.
Main Results:
- The ortho-para conversion rate initially decreased above 0.5 GPa, confirming prior findings.
- A distinct minimum conversion rate was observed at 3 GPa.
- A dramatic increase in the conversion rate was measured, reaching up to 58 GPa.
Conclusions:
- The observed high-pressure enhancement of ortho-para conversion is not explained by existing theories.
- A novel conversion pathway is proposed to account for the unexpected pressure dependence.
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