PhotochemCAD 3: Diverse Modules for Photophysical Calculations with Multiple Spectral Databases.

The PhotochemCAD program, developed over 30 years, is described comprehensively with focus on features of the most recent version (PhotochemCAD 3). The program is equipped with a streamlined user interface and provisions for handling multiple spectral databases. Eight modules enable calculations to be performed on the basis of the spectra in the databases. The calculational modules provide results concerning properties of individual compounds (oscillator strength, transition dipole moment, natural radiative lifetime), interactions of multiple compounds (Förster energy transfer, Dexter energy transfer, analysis of energy transfer among an array of chromophores) and composition of mixtures (multicomponent analysis). Synthetic spectra (blackbody radiator, Gaussian and Lorentzian curves, delta functions) also can be generated. For comparison and calculation, synthetic and experimental spectra can be shifted along both coordinate axes and combined by addition, subtraction and use of multiplicative factors. The core databases (described in the companion paper) have been expanded to 339 compounds for which absorption spectra (including molar absorption coefficient, ε), fluorescence spectra (including fluorescence quantum yield, Φ ) and references to the primary literature have been included where available (552 spectra altogether). A database of 31 solar spectra also is included. Each calculational module is described along with illustrative examples.