Knowledge Bank

The torsional spectrum of ethane has been studied between 225 and $330cm-1$ at a resolution of $0.015cm-1$ using Fourier transform spectroscopy. Observations were made at room temperature, with an absorption path length of 124 m and a pressure of 107 torr. In lowest order, the transition dipole moment arises from Coriolis mixing of the vibrational fundamentals into the ground vibrational state. The P, Q, and R branches of all four torsional sublevels have been measured for the two bands $\nu 4=1\leftarrow 0$ and $v4=2\leftarrow 1$. By analysing over 300 lines in the P and R branches of the fundamental, a good fit was obtained by adapting the torsion-rotation Hamiltonian used for $CH3SiH2.1$ Values will be presented for the height V3 of the six-fold potential barrier, the value of the $\beta$ rotational constant, and three rotation-torsion distorition constants. Work is underway to extend the analysis to the Q branch of the fundamental and to the three branches of the hot band. $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ -M. Wong, I. Ozier, and W.L. Meerts, J. Mol. Spectrose. 89, 111 (1983).