The ultraviolet spectrum of condensed methylamine at 25 K

Using a monochromated synchrotron light source we have recorded the VUV spectrum of a film of solid methylamine, CH3NH2, from 6 to 10 eV. The solid-phase spectrum differs substantially from the gas-phase spectra with lower lying Rydberg states in the gas phase being absent in the solid phase. Vibrational structure visible in the gas phase is also absent in the solid phase. We suggest hydrogen bonding in solid CH3NH2 hinders the ν9 NH2 umbrella mode seen in the gas phase, instead a series of progressions in ν6 (CH3 umbrella) is observed.