A laboratory project for the upper-division physical chemistry laboratory is described combining IR and Raman spectroscopies with Gaussian electronic structure calculations. Students are asked to comment on the differences between the experimental data as well as the differences between the computational and experimental spectra. The main difference between the molecules of interest is the presence or absence of an inversion center. Students measure the IR and Raman spectra of a variety of molecules and carry out Gaussian calculations to predict the vibrational spectra. By considering their results, they assign specific vibrations to those observed in the experimental spectra and explain differences between computational and experimental as well as IR vs. Raman. The complexity of the project immerses the students in vibrational spectroscopy and promotes a deeper understanding of the material.<br/> <br/>In summary, students complete a more thorough investigation of vibrational selection rules using Raman spectroscopy, computational chemistry, and infrared spectroscopy in combination because they provide complementary insight into the molecular structure.<br/> <br/>

Gaining insight into selection rules by combining vibrational spectroscopy with computational chemistry

254th National Meeting (2017)

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