Chronospectroscopy of Exchange-CoupledCr3+-Ion Pairs in Ruby

A rather simple method of determining the lifetimes of the excited states of exchange-coupled ion pairs in ruby is described. The technique utilizes a chopped pump light and phasesensitive detection. It has permitted a great increase in the resolution of optical transitions, and in particular, it allows for a virtual elimination of the vibronic sidebands of the $R$ lines, in order that the true pair spectrum may stand out clearly. Furthermore, transitions originating from different excited levels may be definitely distinguished, thus aiding in the identification of particular transitions with a given pair type. The chronospectroscopic method is of potential value in the studies of energy-transfer mechanisms between single ions and pairs. It has also provided evidence for a fourth-neighbor absorption band at 6050 Å.