The ${\nu }_{11}$ out-of-plane ${\mathrm{CH}}_3$-rocking band of methanol, one of the last fundamentals remaining en route to full vibrational description of this prototype internal rotor, has been identified in the Fourier transform spectrum of ${\mathrm{CH}}_3\mathrm{OH}$ in the $1150{\mathrm{cm}}^{-1\mathrm{}}$ region. The ${\nu }_{11}$ torsional energy pattern is found to be inverted, the first such discovery for a bending state and an important pointer to potential generality of this phenomenon for the whole class of threefold internal rotor molecules. Level-crossing resonances giving transfer channels for intramolecular vibrational energy redistribution (IVR) have been found, and new insights are reported for far-infrared laser emission involving ${\nu }_{11}$ levels.

• Received 1 October 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.3815