Knowledge Bank

The $\nu 14$ vibrational level of furan lies 603 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ above the ground vibrational state. It is the lowest lying vibrational level for which a transition from the ground state is allowed. Other groups have conducted rotational analyses on fundamental bands of furan at 745 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ ($\nu 13$) \textbf{48} (1993) 1193--1202.}, 995 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ ($\nu 7$) \textbf{198} (1999) 348--357.} and at 1067 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ ($\nu 6$) \textbf{209} (2001) 136--138.}. We have taken the rotationally resolved spectrum of the \textit{c}-type $\nu 14$ band at the Canadian Light Source synchrotron with a Bruker IFS125HR Fourier transform spectrometer operating at 0.00096 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ resolution, and have found it to be perturbed by the $\nu 11$ band at 600 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$, for which transitions from the ground vibrational state are forbidden. By taking the spectra of the \textit{b}-type $\nu 18$ fundamental band and of the very weak \textit{c}-type $\nu 18$- $\nu 11$ band we have been able to analyze the $\nu 14$- $\nu 11$ perturbation. We have also analyzed the spectrum of the \textit{b}-type $\nu 19$ fundamental band.