Knowledge Bank

Contrary to the isotopic specie of methanol with a symmetrical CH$3$ or CD$3$ methyl group, in the mono-deuterated species CH$2$DOH the hindering potential no longer displays 3-fold symmetry and all moments of inertia depend on the angle of internal rotation.~{\bf 38} (1963) 54.} For this reason, this mono-deuterated species displays a fairly dense torsional spectrum difficult to compute and to assign. In this paper an analysis of the torsional spectrum of mono-deuterated methanol is presented. More than 40 torsional subbands have been assigned in the 20 to 800~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ region. The body of data available for CH$2$DOH consists of these newly assigned subbands and of the already available ones.~{\bf 239} (2009) 204.} The observed torsional subbands are characterized by $K\le 10$ and $vt\le 10$. For 23 subbands, the rotational structure could be analyzed and this provides us with a mean to check their torsional assignment. The positions of the subband centers were analyzed with a theoretical approach accounting for the dependence of the inertia tensor on the angle of internal rotation. This allowed us to reproduce 58 experimental wavenumbers with an RMS value of 0.12~cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. The spectroscopic parameters corresponding to the hindering potential and to the inertia tensor were also retrieved.