In addition to questions about structure, there exists a discussion regarding the origin of the UV spectrum of OH(aq). It has been suggested that hemibonded configurations are needed to explain the main feature in the aqueous-phase spectrum, which appears at λ ≈ 230 nm and is therefore significantly shifted relative to the gas-phase absorption at λ = 307 nm. The present state of understanding is that the weak Ã 2 Σ + ← X 2 Π transition that is responsible for the gas-phase spectrum is overwhelmed in solution by a charge-transfer transition with a much larger oscillator strength, which is present in hemibonded configurations (where the O is larger. Even if the hemibond is a minority species, it may yet have an outsized role in the spectroscopy of OH(aq). Figure presents absorption spectra of OH(aq) computed using time-dependent (TD-)DFT with three different functionals, for an ensemble of structures obtained from the periodic PBE0 + D3 simulations at T = 370 K. These calculations employ the protocol developed in Ref. 39 and details are provided in the Supporting Information. The three functionals that are used (BH&HLYP, LRC-ωPBE, and OT-LRC-ωPBE) each afford reasonable results for this system as applied to QM/ MM simulations. Figure is plotted in wavelength units and the corresponding spectra in energy units can be found in Fig. , with band maxima listed in Table .