GAS PHASE ROVIBRATIONAL SPECTROSCOPY OF DMSO, PART II: TOWARDS THE TERAHERTZ OBSERVATION OF 4-FOLD CLUSTERS

Abstract

Benefiting of the exceptional properties of the AILES synchrotron beamline, \textbf{1214}, (81), 2010.}, the gas phase Far-IR spectrum of DMSO has been recorded and resolved , \textbf{492},(30),2010}. The rovibrational analysis allowed to discover a new rotational behaviour for a polyatomic molecule: the gyroscopic destabilization. , \textbf{109},(094101), 2012.} In order to explain this phenomenon, we looked for four-fold energy clusters in the high resolution ground state THz spectrum of DMSO recorded with a sub-THz spectrometer based on a frequency multiplication chain , \textbf{13}, 1, 2013.}. Pure rotational lines in the 5 lowest vibrationnally excited levels have been recorded below 700 GHz. With near 1000 rotational transitions assigned, high quantum numbers have been reached allowing to discover sequence of four-fold clusters in the out of plane bending mode of DMSO and to study the vibrational dependence of an unusual rotational dynamics.