T. Momose et al., HIGH-RESOLUTION LASER SPECTROSCOPY OF SOLID PARAHYDROGEN AT LIQUID-HELIUM TEMPERATURES, Czechoslovak journal of Physics, 46, 1996, pp. 529-530
The first overtone vibration-rotation transition of parahydrogen in a
crystal containing a residual amount of orthohydrogen has been detecte
d using high resolution laser spectroscopy. The observed spectrum show
s several splittings due to the anistropic crystal field interactions.
The crystal field splitting of a single J=1 orthohydrogen molecule in
solid parahydrogen at liquid He temperatures is found to be 0.0070cm(
-1) (0.0108 K).