Knowledge Bank

A non-standard high-sensitivity absorption detection technique has been developed and applied to the study of the fifth, sixth, and seventh overtones of HCN, at 100 torr and 296 K. Absolute absorption spectra are directly obtained with a noise level of $2.E-8cm-1$. With regard to the fifth overtones ours constitute a check against previous measurements and a refinement of the absolute band intensities. Our intensities for the 105 and the 006 bands do not agree with previously reported experimental $best-values1$, but they do agree with theoretical $estimates2$. Good agreement with calculated results is also found for the higher overtones, and no evidences for ro-vibrational chaotic dynamics are apparent. Band origins, rotational constants and band intensities are reported in the table. Errors are one standard deviation and the fit constrained the ground state constants to the accurately known values. [FIGURE]