RESOLVING DISCREPANCIES BETWEEN THEORY AND EXPERIMENT - IR-SPECTRUM OF THE PROTON-SHARED HBR-PYRIDINE COMPLEX

The computed MP2/6-31+G(d,p) structure of the HBr:pyridine complex and the computed harmonic and experimental spectra of this complex agree that HBr:pyridine is stabilized by a proton-shared hydrogen bond. Howe ver, differences are evident between the computed and experimental spe ctral patterns with respect to the frequencies and intensities of stro ng bands. Solution of a one-dimensional nuclear vibrational equation a long the normal coordinate mode allows for an estimation of an anharmo nicity of the proton-stretching motion. When an anharmonic stretching force constant is used to recompute the spectrum, excellent agreement is found between theory and experiment.