A rich spectrum composed of hundreds of sharp features (HWHM≲20 MHz) has been observed in the fundamental Q branch of solid ${\mathrm{H}}_2$, representing the first case of solid phase linear spectroscopy in which the high-resolution capabilities of laser spectroscopy have been fully exploited. These features are interpreted as splittings of o-${\mathrm{H}}_2$ pairs based on the work by Hardy, Berlinsky, and Harris.

• Received 20 December 1990

DOI:https://doi.org/10.1103/PhysRevLett.66.2060