Knowledge Bank

Several series of $\Delta J=+1$ transitions have been observed in the rotational spectrum of $CF3NO2$. The spectrum has the same qualitative features as that of $CH3NO2$, but is more complicated. Because the moment of inertia of the $CF3$ group is large, many internal rotation states are populated. In addition, the low asymmetry of the molecule results in a close spacing of the lines over a relatively narrow frequency range so that the Stark effect of most lines is not resolvable and many of the lines themselves cannot be resolved. A number of lines have, however, been assigned and the rotational constants $A(NO2)$, B, and C have been determined. The barrier to internal rotation will be evaluated.