Knowledge Bank

The $4\nu 2$ band of water vapor has been observed for the first time using a heated cell associated with a Fourier transform spectrometer. About 30 lines of this band have been assigned and the band center $4\nu 2=6134.030\pm 0.012cm-1$ together with the rotational constants of the (040) vibrational state have been obtained. Large intensity anomalies are present: only the P branch appears whereas the Q and R branches are almost invisible. Some line intensities have been estimated leading to a total band intensity [S_{v}(4\nu_{2}) = 0.189 \times 10^{-22} cm^{-1}/molecule.cm^{-2}\ at \ 296\ k]