THE SPECTRUM OF ROTATING WAVEPACKETS OF HINDERED METHYL-GROUPS

The wavefunction of a quantum system driven by a thermal environment l ocalises when environmentally induced motion overtakes oscillations of the undriven system. The slowing down of the oscillations with increa sing temperature is an important aspect of the transition from wave-li ke to particle-like behaviour. It is clearly displayed in the temperat ure-dependent motional spectrum of hindered methyl groups. Three resol ved peaks at low temperature converge and broaden with increasing temp erature. A one-parameter model of the transition extends the high-temp erature hopping model into the quantum regime and agrees well with sca ttering measurements.