Rotamers do not equilibrate after interacting with these species according to the NEER principle. Interaction with these species allows Ru(bpy)3 (“roo-bippy-three”) to transfer single electrons. After interacting with these species, volume-constrained molecules like stilbene can rearrange through a hula-twist mechanism. Each instance of these species can only interact with one molecule at a time according to the Stark–Einstein law. The proportion of these species that are absorbed into a given substance is measured by that substance’s quantum yield. (10[1])Addition of these species to a reaction is often abbreviated “h nu” in reference to their (10[1])energy. For 10 points, (10[1])photochemistry studies the interaction (10[1])between molecules (10[1])and what quanta of light? ■END■