Molecular Motion and Interactions in Solid Hydrogen Studied by High Resolution Infrared Spectroscopy

In this thesis, high resolution infrared spectrum of tetrahexacontapole (64-pole)-induced rovibrational W transition of solid parahydrogen (para-H2) was studied in samples containing ∼0.05% of orthohydrogen (ortho-H2) using high resolution near infrared diode laser spectroscopy. The rovibrational W1(0) transition (v =1 ← 0,J = 6 ← 0) has been observed at ∼6441.73 cm-1 with resolved triplet structure. These components were interpreted as the splitting of the M levels in the v = 1, J = 6 state due to crystal field interaction. The corresponding crystal field parameters based on the model of localized exciton in the W1(0) transition were determined. The good agreement of the corresponding parameters between the W1(0) transition and the previous W0(0) transition confirms the localization of the J =6 roton in both v = 0 and 1 states for solid para-H2. In addition, the temperature dependence of the W1(0) transition was studied in the temperature range of 2.7-8.0 K. The observed frequency shift has been ascribed to the change of isotropic intermolecular interactions as a result of molar volume change at different temperature.;In an attempt at studying tunneling motions in the solid para -H2, the infrared absorption spectrum of matrix-isolated ammonia molecules (NH3) has been studied using Fourier-transform infrared (FTIR) spectroscopy. The transitions of the ammonia molecule in the v2 fundamental band were observed to exhibit very different pattern compared to those observed in other matrix materials. A preliminary analysis of the observed spectrum was also discussed based on the effect of crystal annealing and nuclear spin conversion of NH3. Transitions have been assigned to ortho and para species of NH3 based on there behavior in the presence of O2. For a more definitive assignment, further experiments will be necessary.