High resolution infrared spectroscopy of some molecules in the gas phase

A nineteen-parameter harmonic in-plane force field for the s-trifluorobenzene-h3 molecule was constructed. Internal force constants, symmetry force constants, normal coordinates and Cartesian displacements were calculated. The observed data included fundamental frequencies, first order Coriolis constants and centrifugal distortion constants for both s-trifluorobenzene-h3 and -d3. Some of the data were obtained from our study of the mid-infrared spectrum of s-trifluorobenzene-h3. A seven-parameter harmonic out-of-plane force field for the same molecule was also re-investigated, utilising two accurately obtained fundamental frequencies. The mid-infrared spectrum of s-trifluorobenzene-h3 was examined at a resolution of ca. 0.06 cm-1 . An analysis of the two partially resolved fundamental a2 vibrations was completed using the method of simulation with synthetic spectra. The five e' fundamental bands of the same molecule in the mid-infrared region were investigated for the estimation of first order Coriolis constants. A modified computer program was used to simulate the effects of l-resonance which were present in some of the fundamentals. The infrared spectra of some of the overtones and combination bands were also investigated and in some cases effective first order Coriolis constants were estimated either using computer simulation techniques or zeta sum rules or both. The mid-infrared spectra of two deuterium substituted propynal molecules, namely C2H.CDO and C2D.CDO were recorded at a resolution of ca. 0.08 cm-1. A detailed analysis of the partially resolved v1(a'), v5(a'), v6, v10(a', a'') bands of C2H.CDO molecule was completed. An analysis of v7 and v11 bands of the same molecule was also performed. Again, the method which was used was the simulation of the observed bands with synthetic spectra taking into account the effects of second order Coriolis interactions between the energy levels of the two bands. Finally, the v6(a') , v10(a' ') pair of bands of C2D.CDO species were also analysed, again using the 'Band Contour Method'