A. Discuss the physical origins of the gross selection rules for infrared spectroscopy and Raman spectroscopy. Suppose that you wish to characterize the normal modes of benzene in the gas phase. Why is it important to obtain both infrared absorption and Raman spectra of your sample?

b. The vibrational wavenumber of a diatomic molecule in its electronic state is 2600 cm^-1, whereas that in the first excited state is 2000 cm^-1. The separation in energy between the minima in their respective potential energy curves of these two electronic states is 5.0 eV. Calculate the 5 lowest energy transitions originating from the n=0 vibrational state of the electronic ground state to the vibrational states of the excited electronic state. (Both electronic ground and excited states can be considered as harmonic oscillators.)