PHOTOSTABILITY OF AQUEOUS MICELLAR RHODAMINE-6G LASER-DYE SOLUTIONS UNDER XECL LASER PUMPING

The photostability of concentrated (10-3-3×10-3M) rhodamine 6G (R6G) solutions has been investigated in high repetition rate (250 Hz) XeCl laser pumped dye lasers. In 10-1 M sodium dodecylsulfate (SDS) aqueous solution the R6G photodegradation is faster than in methanol. We conclude to a two photon excitation at 308 nm, {A figure is presented} due to a strong increase of the 308 nm absorbance during the laser pumping. We determined the S1 absorption spectrum and calculated σ308nmS = (4.6 ±0.5) × 10-17 cm2 the absorption cross section of the S1 state. We believe that the S*n ionization (S*n→ R+. + e-) of R6G is more efficient in SDS aqueous solution and that the recombination of the radical (R+.) with the resulting hydrated electron (e-aq) is prevented by the repulsive electrostatic surface potential of the SDS negative interface. © 1990.