Mountaineering Strategy to Excited States: Highly Accurate Oscillator Strengths and Dipole Moments of Small Molecules.

This work presents a series of highly accurate excited-state properties obtained using high-order coupled-cluster (CC) calculations performed with a series of diffuse containing basis sets, and extensive comparisons with experimental values. Indeed, we have computed the main ground-to-excited transition property, the oscillator strength, and the ground- and excited-state dipole moments, considering 13 small molecules (hydridoboron, hydrogen chloride, water, hydrogen sulfide, boron fluoride, carbon monoxide, dinitrogen, ethylene, formaldehyde, thioformaldehyde, nitroxyl, fluorocarbene, and silylidene). We systematically include corrections up to the quintuple (CCSDTQP) in the CC expansion and extrapolate to the complete basis set limit. When comparisons with experimental measurements are possible, that is, when a number of consistent experimental data can be found, theory typically provides values falling within the experimental error bar for the excited-state properties. Besides completing our previous studies focused on transition energies [J. Chem. Theory Comput. 14 (2018) 4360-4379, ibid. 15 (2019) 1939-1956, ibid. 16 (2020) 1711-1741, and ibid. 16 (2020) 3720-3736], this work also provides ultra-accurate dipoles and oscillator strengths that could be employed for future theoretical benchmarks.