Energy transfer between collagen-dye molecules as a probe of higher-lying electronic states following multiquantum excitation

Under high-intensity nanosecond 1064 nm irradiation of a collagen-rhodamine 60 (R6G) system, multiquantum excitation of the R6G molecules to their S-2 state was facilitated. The observation of this effect was achieved through associated energy transfer to the resonant collagen excited state band. An alogous cascaded energy transfer phenomena, resulting from the S-2 electron ic state of R6G, were observed in an R6G-collagen-coumarin system.