Photophysics of UV-excited Cl2CS in a perfluoroalkane solvent

Abstract

The quantum yields of fluorescence from UV-excited Cl₂CS in inert perfluoroalkane solutions have been measured as a function of the analytical concentration of the solute in the range 5 × 10^–5⩽C/mol dm^–3⩽ 1, and as a function of excitation energy in the range 245 ⩽λ_ex/nm ⩽ 330. The excited-state decay rates have also been measured at 272 ⩽λ_ex/nm ⩽ 300 over the same concentration range. A quantitative description of the photophysics of the system has been achieved, which accounts for significant self-aggregation of the ground state solute at C > 10^–4 mol dm^–3, absorption by a nearby dark excited state of the monomer in the 285 ⩽λ_ex/nm ⩽ 330 range, different lifetimes and rate constants of concentration quenching of the excited monomer and the excited dimer, and the excitation wavelength dependence of fluorescence-weakening non-radiative relaxation processes in each excited species.