Alignment of CH3F in para-H2 crystal studied by IR quantum cascade laser polarization spectroscopy

In order to investigate the alignment of CH3F in para-H2 crystals, high resolution polarization spectroscopy of the ν 3 vibrational band is studied using a quantum cascade laser at 1040 cm−1. It is found that the main and satellite series of peaks in the ν 3 vibrational band of CH3F have the same polarization dependence. This result supports the previously proposed cluster model with ortho-H2 in first and second nearest neighbor sites. The observed polarization dependence function is well described by a simple six-axis void model in which CH3F is not aligned along the c-axis of the crystal but tilted to 64.9(3)° from it.