Analysis of the ν7+ν9 and 2ν7−ν9 band complexes of dicyanoacetylene (NC–CC–CN)
Infrared gas spectrum
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The very weak ν7+ν9 band complex near 368 cm-1 and the 2ν70-ν9 system near 404 cm-1 in the infrared gas spectrum of dicyanoacetylene (NC-CC-CN) have been analysed. In the ν7+ν9 band system, we have assigned 68 subbands, reaching upper vibrational states with ν7 up to 3 and ν9 up to 8. The 11 subbands of the 2ν70-ν9 system with ν9 up to 7 could be observed because of intensity transfer from the ν3-ν9 band, a result of the strong anharmonic interaction between the ν3 and 2ν70 states. The combined data from the previously studied ν9 band together with the ν7+ν9 and 2ν7-ν9 bands were used for a global rovibrational analysis from which a full set of molecular parameters for the ν7 and ν9 modes has been deduced. A recently developed theory of intensities in such band systems has been applied to the ν7+ν9 band. Examples of intensity calculations illustrate some spectacular effects of the rotational and vibrational ℓ-type resonances on intensities. The observed intensities are in good agreement with the predicted values within the expected J-ranges.
CitationWinther, F.; Horneman, V.-M.; Vigouroux, C.; Fayt, A. (2005). Analysis of the ν7+ν9 and 2ν7−ν9 band complexes of dicyanoacetylene (NC–CC–CN). , Journal of Molecular Structure, Vol. 742, Issue 1-3, 131-146, DOI: 10.1016/j.molstruc.2005.01.011.