Internal Rotation and Spin Conversion of CH3 OH in Solid para-Hydrogen.

The quantum solid para-hydrogen (p-H[sub 2]) has recently proven useful in matrix isolation spectroscopy. Spectral lines of compounds embedded in this host are unusually narrow, and several species have been reported to rotate in p-H[sub 2]. We found that a p-H[sub 2] matrix inhibits rotation of isolated methanol (CH[sub 3]OH) but still allows internal rotation about the C-O bond, with splittings of the E/A torsional doublet in internal rotation — coupled vibrational modes that are qualitatively consistent with those for CH[sub 3]OH in the gaseous phase. This simplified high-resolution spectrum further revealed the slow conversion of nuclear spin symmetry from species E to species A in the host matrix, offering potential insight into nuclear spin conversion in astrophysical sources. [ABSTRACT FROM AUTHOR]