Determination of photoisomerization parameters for a PMMA thin film doped with disperse orange 3

Abstract An analytic absorption function was derived to investigate the dynamics of photoisomerization in a poly(methyl methacrylate) thin film doped with disperse orange 3 (DO3). The temporal absorption measured using the pump-probe method was well-behaved, following an analytic function with a single exponential term. The isomerization and thermal-relaxation rates were evaluated by curve-fitting. The analytic absorption function was validated by measuring the thermal-relaxation rates with the pump separately on and off. Using this function, an analytic method for determining the photoisomerization parameters was demonstrated: for DO3 in poly(methyl methacrylate), the photoisomerization quantum yields for trans-cis and cis-trans processes were determined to be ϕ TC = 0.12 ± 0.01 and ϕ CT = 0.77 ± 0.06 , respectively. The absorption cross section for the cis isomer was measured to be σ C = ( 0.92 ± 0.03 ) × 10 − 16 cm 2 . This analytic method can thus be used to characterize the dynamics of photoisomerization in dye doped thin films.