Knowledge Bank

The perpendicular infrared bands of the $E\prime$ vibrations of $C3-B5$ were measured on a large FT spectrometer at resolution approaching the Doppler limit. The unperturbed $\nu 11$ band provided the most extensive data yielding 867 combination differences for a determination of accurate ground state constants $B0$ and $DJ$. These were combined with highly accurate values of $C0-B0$ and $DJK$ recently determined by Baudar {et al.} from an FTMW measurement of the rotational spectrum: $ B_{0} = 0.4613514(4), C_{0} = 0.3182425(4), D^{0}{J}= 3.7868(18) \times 10^{-7}, D^{0}{JK} = -3.7395(7) \times 10^{-7}$ (all $incm-1$ units). The $\nu 10$ band was found to have an appearance of a parallel band due to an accidental match of the values of $(C\zeta )10$ and $B\prime -C\prime$. The $\nu 9$ band exhibits a perturbation in its P-branches due to Fermi resonance with $2\nu 214$. Spectroscopic constants for the upper states $\nu 11,\nu 10,\nu 9$, and $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\nu 214$, obtained from a detailed rotational analysis of the three bands will be reported.