Absorption Intensities of Organic Molecules from Electronic Structure Calculations versus Experiments: the Effect of Solvation, Method, Basis Set, and Transition Moment Gauge.

Recently, we derived experimental oscillator strengths (OSs) from well-defined UV-visible absorption spectral peaks of 100 molecules in solution. Here, we focus on a subset of transitions with the highest reliability to further benchmark the OSs from several wave function methods and density functionals. We consider multiple basis sets, transition moment gauges (length, velocity, and mixed), and solvent corrections.

OS100: A Benchmark Set of 100 Digitized UV-Visible Spectra and Derived Experimental Oscillator Strengths.

Excited-state quantum chemical calculations usually report excitation energies and oscillator strengths, , for each electronic transition. On the other hand, UV-visible spectrophotometric experiments measure energy-dependent molar extinction/attenuation coefficients, ε(), that give absorption band line shapes when plotted. ε() and are related, but this relation is complicated by broadening and solvation effects.