Knowledge Bank

Recent progress in analysis and fitting of transitions in the toluene microwave spectrum characterized by $J$$\leq$30, $K$$\leq$12, and the free rotor quantum number $|$$m$$|$$\leq$3\; will\; be\; presented.\; The\; analysis\; was\; carried\; out\; using\; a\; new\; program\; which\; is\; specifically\; designed\; for\; six-fold\; barrier\; molecules,\; and\; allows\; the\; user\; to\; select\; almost\; any\; symmetry-allowed\; torsion-rotation\; term\; for\; inclusion\; in\; the\; fitting\; Hamiltonian.\; The\; program\; is\; based\; on\; the\; theoretical\; framework\; developed\; by\; S\{\backslash o\}rensen\; and\; Pedersenrensen,\; T.~Pedersen,\; \{\backslash it\; Studies\; in\; Physical\; and\; Theoretical\; Chemistry\},\; Elsevier,\; \{\backslash bf\; 23\},\; 219--236\; (1983).\}\; in\; their\; application\; of\; the\; Longuet-Higgins\; permutation-inversion\; group\; G$_{12}$ to the microwave spectrum of CH$3$NO$2$. In the analysis we have used the published and rather extensive unpublished data from previous studies as well as recent new measurements of the toluene microwave spectrum in the 8 -- 18 GHz range. A rather successful fit of over 350 toluene microwave transitions in the abovementioned quantum number range has been achieved. The fit is close to the estimated experimental accuracy and includes more than thirty intertorsional $m$=~+3 $\iff$ $m$=~-3 transitions.