Revision 1

Accepted · first revision · record

Title: Excitation energies of large chromophores to 0.05 eV
Plain: Reference excitation energies accurate to a few hundredths of an electronvolt exist for small molecules. For the larger dye and protein pigment molecules that matter in practice, methods still disagree by more than that.
Precise: For molecules of 10 to 30 non-hydrogen atoms (the larger molecules of the QUEST sets, and gas-phase biological chromophores such as the green fluorescent protein chromophore anion and the protonated retinal Schiff base), determine vertical excitation energies of the lowest singlet and triplet states to 0.05 eV, and identify the lowest-cost method that reaches mean absolute error below 0.05 eV. An answer is theoretical best estimates confirmed by two independent high-order methods plus the method benchmark, cross-checked against gas-phase absorption spectra.
Settled by: Agreement of high-order coupled cluster and selected configuration interaction in the complete basis limit with gas-phase action spectroscopy.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)