15min:
GAS PHASE ROVIBRATIONAL SPECTROSCOPY OF DMSO, PART.I: WHEN A SYNCHROTRON SOURCE REVEALS AN UNUSUAL ROTATIONAL BEHAVIOUR .

ARNAUD CUISSET, DMITRII A. SADOVSKII, Laboratoire de Physico-Chimie de l'Atmosphère, 189A Ave. Maurice Schumann, 59140 Dunkerque, France; OLIVIER PIRALI, Ligne AILES, synchrotron SOLEIL, L'Orme des Merisiers, Saint Aubin, BP 48, 91192 Gif-sur-Yvette, France..

Many of us have enjoyed the spectacle of a spinning top influenced by friction: rotating rapidly about a stable stationary axis, the top loses slowly its angular momentum j (and energy), slows down gradually, and then, suddenly, its axis becomes unstable, the top wobbles, and an abrupt change of the top’s position follows. In other words, the system undergoes a bifurcation. In the case of the tippe top, rotation about its lower point is stable at low values of angular momentum J and becomes unstable at large J. Something quite similar occurs in a freely rotating dimethylsulfoxyde (DMSO, (CH3)2SO) molecule. For the first time in such large polyatomic molecule a quantum bifurcation induced by a gyroscopic destabilization was observed. This unusual phenomenon in rotational dynamics was discovered in the rovibrational states of the bending fundamental nu23 band of DMSO whose high-resolution gas phase absorption spectrum was observed along with that of nu11 by Cuisset et al. using the exceptional properties of the AILES beamline in the Far-Infrared domain.