TRANSIENT ABSORPTION OF THE PROBE BEAM BY THE ERYTHROSINE TRIPLET IN PULSED-LASER THERMAL LENS SPECTROMETRY - THE INFLUENCE OF THE SOLVENT,OXYGEN AND DYE CONCENTRATION

Transient absorption of the probe beam by the erythrosine triplet gene rated by excitation laser is evidenced in pulsed-laser thermal lens sp ectrometry. The transient absorption signal and thermal lens signal ex hibit nonlinear dependences against excitation energy accounting for p hotobleaching of ground-state species with subsequent production of me tastable triplets. By careful adjustment of the probe and excitation b eam waists into the sample cell, the thermal lens signal can be remove d and only the transient absorption signal detected. The lifetime of t he tripler state is investigated from the decay rate constant of the t ransient signal. In nitrogen-saturated solutions, the decay rate depen ds on the solvent and dye concentrations. The quenching rate constants obtained in homogeneous solvents, such as water and ethylene glycol, are typical of diffusion-controlled reactions and depend on the viscos ity. In aqueous micellar solutions, self-quenching is less operative d ue to the protecting effect of micelles and the tripler state would de activate mainly by unimolecular decay. (C) 1998 Elsevier Science B.V. All rights reserved.