TRANSIENT EFFECTS AND THE IDENTIFIABILITY OF EXCITED-STATE PROCESSES

The identifiability of excited-state processes in the presence of tran sient effects is studied. The Smoluchowski and Collins-Kimball models of diffusion-mediated association are considered. The kinetic paramete rs of single-species quenching and related kinetic schemes (double-spe cies quenching without excited-state interchange, and irreversible ass ociation with separated excited-species spectra) can be uniquely recov ered from the same or a smaller number of decay traces than are necess ary within classical kinetics where time-invariant rate constants are used. For single-species quenching in low dimensions, 1D and 2D, the s ystem parameters can be uniquely recovered from a single decay trace a t one nonzero quencher concentration. In three dimensions, decays trac es measured at two concentrations are necessary and sufficient to reco ver the parameters. For double-species quenching without interchange o f the excited states, decay traces at two wavelengths collected in the absence and presence of quencher guarantee local identifiability of t he model in each dimension with or without transient effects. Irrevers ible association with separate excited-species spectra is identifiable in each dimension, given decay traces at two quencher concentrations and two wavelengths.