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

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 ϕTC=0.12±0.01 and ϕCT=0.77±0.06, respectively. The absorption cross section for the cis isomer was measured to be σC=(0.92±0.03)×10−16cm2. This analytic method can thus be used to characterize the dynamics of photoisomerization in dye doped thin films.