Explain briefly the information one can get from vibrational analysis of electronic vibration spectra.
Answers
Vibronic spectroscopy may provide information, such as bond-length, on electronic excited states of stable molecules. It has also been applied to the study of unstable molecules such as dicarbon, C2, in discharges, flames and astronomical objects.Electronic transitions are typically observed in the visible and ultraviolet regions, in the wavelength range approximately 200–700 nm (50,000–14,000 cm−1), whereas fundamental vibrations are observed below about 4000 cm−1.[note 1] When the electronic and vibrational energy changes are so different, vibronic coupling (mixing of electronic and vibrational wave functions) can be neglected and the energy of a vibronic level can be taken as the sum of the electronic and vibrational (and rotational) energies; that is, the Born–Oppenheimer approximation applies.[4] The overall molecular energy depends not only on the electronic state but also on vibrational and rotational quantum numbers, denoted v and J respectively for diatomic molecules. It is conventional to add a double prime (v", J") for levels of the electronic ground state and a single prime (v', J') for electronically excited states.