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Observation of Rotational Excitation in Dense Hydrogens
Phys. Rev. Lett. 136, 016101 – Published 5 January, 2026
DOI: https://doi.org/10.1103/7m51-n6w7
Abstract
Raman measurements performed on dense , and in a wide pressure-temperature range reveal the presence of the rotational excitation. In the gas/fluid state this excitation has zero Raman shift, but in the solid, the crystal field drives it away from the zero value, e.g., at around 50 GPa and 10 K for both isotopes and their mixture. In the case of deuterium, the mode splits upon entering phase II suggesting a very complex molecular environment of the broken symmetry phase (BSP). In the fluid state and phases I and II the frequencies (energies) of the transition for and scale neither as rotational (by factor of 2) nor vibrational (by ) modes and appear to be completely isotope independent. This independence on mass marks this transition as unique and a fundamentally different type of excitation from the commonly considered harmonic oscillator and quantum rotor.
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