Carbonhyphen;13 Impurity Effect on thea2uInfrared Exciton Spectrum of the Benzene Crystal

摘要

The Chyphen;13 shift for thea2umolecularbenzene mode has been calculated to beminus;0.33 plusmn; 0.04thinsp;cmminus;1.This confirms our previous assignment of the major pairwise molecular excitation exchange interactions for thea2uvibrational exciton and enables us to pick an exciton densityhyphen;ofhyphen;states for the pure crystal. We also calculate the naturalhyphen;abundance isotopically mixed benzene crystal densityhyphen;ofhyphen;states and its spectrum. Predicted inhyphen;band spectral resonances are consistent with published experimental data and facilitate their interpretation in terms of Davydov components, densityhyphen;ofhyphen;states peaks, band center, site shift, and exciton interactions. The implications and applications of the Chyphen;13 presence in ``pure crystal'' spectra are discussed.