Quantum property of solid hydrogen as revealed by high-resolution laser spectroscopy

Pure vibrational overtone transitions of solid parahydrogen are studied using high-resolution laser spectroscopy. Extremely narrow spectral linewidth (similar to20 MHz) allows us to observe rich spectral structure that originates in subtle intermolecular interactions in the crystal. It is found that anisotropy of the distribution of zero-point lattice vibration of hydrogen molecules perturbs the energy levels of the vibrationally excited states significantly. A large amplitude of zero-point lattice vibration, an intrinsic propoerty of quantum solids, is directly observed from the present high-resolution spectroscopy. The first observation of a pure vibrational overtone transition of solid orthodeuterium is also discussed. (C) 2003 American Institute of Physics.