Laser selected fluorescence of human cataractous lenses at liquid helium temperatures

Laser excitation of an inhomogeneous distribution of chromophors at temperatures near 0 K is known to result in sharp fluorescence spectra in numerous systems. When this technique was applied to human cataractous lenses at 4 K, broad fluorescence resulted. The wavelengths of maximum fluorescence were different from those previously reported, thus demonstrating the observation of new fluorophors. The broad fluorescence appears to result from internal conversion and energy transfer processes and not from low frequency vibrational motions or strong vibronic coupling. Consequently, other site selection techniques, such as spectral hole burning, may produce sharp spectra with vibronic structure that can be used to identify the molecular species involved.