The preferred experimental set of signs for the part;p/part;Qirsquo;s of C6H6and C6D6have been determined from the gas phase infrared intensities of these molecules. This set for C6H6is in agreement with the one found previously for this molecule based on data for C6H6, C6H5D, andphyphen;C6H4D2. Polar tensors, atomic mean dipole moment derivatives, anisotropies, and effective charges for C6H6, C6D6, and C6F6are reported. The isotopic invariance of these quantities as indicators of the correct sign choice for the part;p/part;Qirsquo;s is investigated for C6H6and C6D6. Several applications of theGhyphen;sum rule are made: (a) its usefulness in pointing out the correct signs of the part;p/part;Qiis investigated, (b) corrected values for the intensity sums of C6H5D andphyphen;C6H4D2are calculated, and (c) intensity sums for C6H4F2and C6H2F4are predicted.
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