ABSTRACT
Electronic energy levels are more widely separated than vibrational or rotational energy levels because considerably more energy is needed to change the distribution (i.e. configuration) of electrons in atomic or molecular orbitals than to change the energy of vibration or rotation. Consequently, electronic spectroscopy is usually associated with the visible or ultraviolet regions of the spectrum. The colors of many objects, for example vegetation, flowers, minerals, paints and dyes, are all due to transitions of electrons from one molecular orbital to another (see Topic I7).
