HIGH RESOLUTION INFRARED ABSORPTION SPECTROSCOPY OF THE FIRST OVERTONE PURE VIBRATIONAL TRANSITION $Q_{2}(0)$ OF SOLID PARAHYDROGEN

$^{a}$ T. Momose, T. Wakabayashi, and Shida, J. Opt. Soc. Am. B 13, 1706 (1996). $^{b}$ R. M. Dickson, T. Momose, T. J. Byers, and T. Oka, Phys. Rev. B 57, 941 (1998).Author Institution: Division of Chemistry, Graduate School of Science Kyoto UniversityIt has been shown that high-resolution infrared spectroscopy is applicable to the zero-phonon transitions of rotons and vibrons in solid hydrogen. Because the pure vibrational transitions $Q_{n}(0) [v=n \leftarrow 0, J = 0 \leftarrow 0]$ of solid parahydrogen become infrared-active only upon interaction with residual $J=1$ orthohydrogen, studies of the pure vibrational transitions under high-resolution provide detailed and accurate information on intermolecular interactions between hydrogen molecules. Here, we report the high-resolution absorption spectrum of the first overtone pure vibrational transition $Q_{2}(0)$ of solid parahydrogen. The high-resolution spectrum of the $Q_{2}(0)$ transition at around $8070 cm^{-1}$ was observed using a difference frequency laser $system^{a}$. The spectrum shows a complicated spectral feature compared with that of the $Q_{3}(0)$ $transition^{b}$. The $v=3$ vibrational exciton was found to be well localized on the parahydrogen molecule next to an orthohydrogen. On the other hand, since the vibron hopping matrix element of the $v=2$ state is comparable to the energy shift due to the existence of orthohydrogen, the observed rich spectral structure can be interpreted as due to the $v=2$ vibron hopping over a limited number of lattice sites in the crystal. We will discuss the quantitative analysis of the observed spectrum