Comparison of the Single-Wavelength and Spectral-Reconstruction Methods for Determining the Solvation-Response Function

A comparison of the solvation/spectral-response functions obtained by two independent techniques, the single- wavelength and spectral-reconstruction methods, is reported. Determination of the best wavelengths for application of the linear-single-wavelength approximation for the solute coumarin 153 (C153) is achieved using radiative rate data and steady-state emission spectra in a series of 36 different solvents at room temperature. The optimal linear wavelength is found to be 555 nm. (This wavelength, which is on the red side of the spectrum, yields superior results when compared to the more traditional choice of 470-480 nm, on the blue side.) Response functions determined using both 560- and 470-nm observation wavelengths are compared to previously reported spectral-reconstruction results in 24 solvents. A comparison of the characteristic times indicates that the linear-single-wavelength method can be used to predict solvation times with an accuracy of roughly ±30-40% (1 standard deviation) using suitably scaled data collected at ∼560 nm. Application of a nonlinear version of the single-wavelength method does not provide increased accuracy.