# FOURIER-TRANSFORM MICROWAVE AND 10 MICRON INFRARED MOLECULAR BEAM SPECTRA AND ANHARMONIC COUPLINGS IN 1, 1, 1, 2-TETRAFLUOROETHANE

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 Title: FOURIER-TRANSFORM MICROWAVE AND 10 MICRON INFRARED MOLECULAR BEAM SPECTRA AND ANHARMONIC COUPLINGS IN 1, 1, 1, 2-TETRAFLUOROETHANE Creators: Xu, Li-Hong; Andrews, Anne M.; Fraser, G. T.; Grabow, Jens-Uwe; Lovas, F. J.; Stahl, W. Issue Date: 1995 Abstract: A microwave-sideband $CO_{2}$ laser and an electric-resonance optothermal spectrometer have been used to observe the 2 MHz resolution infrared spectrum of 1, 1, 1, 2-tetrafluoroethane near the vicinity of the low-resolution gas-cell feature at $972.4 cm^{-1}$, attributed to the $\nu_{15} a^{\prime\prime} CH_{2}$ rock. In our molecular-beam experiments two C-type bands of nearly equal intensity are observed with origins at 974.35 and $974.87 cm^{-1}$, only one of which is a normal mode vibration. Initial assignments are established by microwave-infrared double resonance using the precise microwave frequencies and molecular constants obtained for the vibrational ground state with a Fourier-transform microwave spectrometer, New isotopic ground state microwave measurements have also been made to refine the ground state structural determination. The observed infrared band types establish that the two upper state vibrations are both of $a^{\prime\prime}$' symmetry. Anharmonic mixing of the two upper states gives the nearly 50:50 intensity ratio and leads to poor characterization of the rotational progressions by standard asymmetric rotor treatments, Efforts are presently underway to undertake a simultaneous fitting of the two bands and to identify the perturbing state. URI: http://hdl.handle.net/1811/29678 Other Identifiers: 1995-RI-08