An aqueous cobalt(II) complex is studied with a spectrophotometer. The instrument reports a single, sharp absorption maximum at 580 nm with an absorbance of 0.88 under the experimental conditions.
Assume each absorbed photon promotes one electron from its ground electronic state to the first excited electronic state of the complex.
(a) Identify the region of the electromagnetic spectrum in which the 580 nm peak lies and state the corresponding type of molecular transition.
(b) Calculate the energy, in kJ mol−1, associated with this electronic transition. Use h=6.626×10−34J s, c=3.00×108m s−1, and NA=6.022×1023mol−1.
(c) Explain how the magnitude of the energy you calculated compares with typical vibrational transition energies, and discuss what this implies about the spacing of electronic versus vibrational energy levels in molecules.