# ANALYSIS OF THE $3 \mu m$ BANDS OF BENZENE

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 Title: ANALYSIS OF THE $3 \mu m$ BANDS OF BENZENE Creators: Pliva, J.; Pine, A. S. Issue Date: 1987 Publisher: Ohio State University Abstract: A comprehensive rovibrational analysis is reported for the $3 \mu m$ absorption bands of the benzene molecule measured on a difference-frequency laser spectrometer and deconvolved to an effective linewidth of $0.0010 - 0.0015 cm^{-1}$. The four strong bands observed, centered at 3047.908, 3078.614, 3100.408, and $3101.854 cm^{-1}$, are due to the $E_{1u}$ fundamental $\nu_{12}$ sharing its intensity with the $E_{1u}$ components of the states $\nu_{13}\cdot \nu_{16}, \nu_{2}\cdot \nu_{3}\cdot \nu_{18}$ and $\nu_{3}\cdot \nu_{10}\cdot \nu_{18}$ via anharmonic resonances. The bands exhibit strong perturbations due to 1-resonances with the inactive $B_{1u}/B_{2u}$ components of the $\nu_{13}\cdot \nu_{16}$ and $\nu_{2}\cdot \nu_{13}\cdot \nu_{18}$ states, and numerous localized perturbations due to overtones and combinations of the 16 low frequency vibrations of the molecule. Symmetry arguments and values of constants such as $C\zeta$ known for the fundamentals have been used to propose tentative assignments for many of the perturbing states. A Hamiltonian matrix containing all components of the main interacting states plus 18 perturbing states was used for the treatment of $\sim 8400$ assigned transitions. A set of spectroscopic constants is reported which reproduces all the data with a standard deviation of $0.0012 cm^{-1}$. It is found that x,y-Coriolis and anharmonic resonances of surprisingly high order have to be invoked to account for most of the localized perturbations observed in the spectrum. Description: Author Institution: Department of Physics, The Pennsylvania State University; Molecular Spectroscopy Division, National Bureau of Standards URI: http://hdl.handle.net/1811/17207 Other Identifiers: 1987-MF-5