FTIR and dispersive gas phase fundamental infrared intensities of the fluorochloromethanes: Comparison with QCISD/cc-pVTZ results

New experimental values of the fundamental infrared gas phase intensities of the fluorochloromethanes have been determined by integrating the areas of vibrational bands contained in the PNNL spectral library using homemade software. The root mean square differences of these values and averages of experimental values determined at lower resolution during the latter part of the 20th century is 26.6 km mol(-1). All but one of the low resolution intensities are smaller than the PNNL values. The exception is the v(1),v(4) overlapped band intensity of CF3CI that has a standard deviation of the low resolution values of +/- 112.5 km mol(-1), larger than the observed difference of 102.5 km mol(-1). The use of an augmented triple zeta basis set at the QCISD level results in an rms difference of only 8.4 km mol(-1) for the fluoro- and chloromethane PNNL intensities, whereas a comparison of these with results at the QCISD/cc-pVTZ level produces an error twice as large, 16.2 km mol(-1). As such these results suggest that future comparisons of theoretical intensities with experimental values should take into account integrated intensities that can be obtained from hundreds of spectra in the PNNL library. Furthermore, the intensity values obtained from the PNNL spectra confirm electronegativity model results previously reported based on the low resolution intensities. (C) 2018 Elsevier B.V. All rights reserved.