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Variation of intermolecular interaction and local lattice distortion of parahydrogen crystals upon vibrational excitation

1998; American Physical Society; Volume: 57; Issue: 2 Linguagem: Inglês

10.1103/physrevb.57.950

1095-3795

Robert M. Dickson, Takeshi Oka,

Cold Atom Physics and Bose-Einstein Condensates

When a hydrogen molecule in a parahydrogen crystal is excited to a high vibrational overtone state, its electronic properties vary significantly since the energy of excitation is a sizable fraction of the energies of the excited electronic states. Thus the vibrational excitation leads to a significant variation of the intermolecular potential and resultant local distortion of the crystal lattice. Such an effect is sensed by the variation of the splitting of $M$ sublevels of the $J=1$ ${\mathrm{H}}_{2}$ impurity that causes the overtone transition. In this paper we attempt to theoretically explain the observed large variations of the pair and crystal-field splitting parameters $\ensuremath{\Delta}B$ and ${\ensuremath{\varepsilon}}_{2c}$ upon the $v=3\ensuremath{\leftarrow}0$ vibrational excitation. Using the ab initio anisotropic intermolecular pair potential and simplified models on the vibrational dependence of the potential and crystal distortion, observed values are well explained.