sequence of geometries adopted by a molecule after initial electronic excitation, combined with a specification of the electronic state at each geometry, from radiation absorption to product formation. Theoretically, this usually involves the computation of the MERP connecting the Franck–Condon point, located on the potential-energy surface of the spectroscopic state, to the final photoproducts located on the ground-state potential ?energy surface. Experimentally, a photochemical reaction path can be probed by detecting transient species or reaction intermediates.