Erratum: Solvent Polarity under Vibrational Strong Coupling

In a research article published last year we reported red shifting of the charge transfer band of Reichardt’s dye in the visible spectrum when the solvent was vibrationally coupled to an optical cavity, indicating a change in the polarity of the solvent. The magnitude of the observed shifts correlated with the alkyl chain length of the alcohol solvents and with their polarizability and solvent-accessible surface area. Control experiments under off-resonance conditions in which none of the vibrational bands of interest were coupled to the cavity showed no shifts. We interpreted these experiments as evidence that strong coupling is responsible for the observed shifting, and that the change in solvent polarity was due to the impact of vibrational strong coupling (VSC) on London dispersion forces within the coupled solvent. However, additional experiments and transfer matrix simulations (TMS) to mimic the transmission of light through the optical Fabry Perot (FP) cavity have caused us to revisit this interpretation. We now believe that the observed shifts for Reichardt’s dye were an optical artifact caused by neglecting reflection when measuring absorbance in transmission mode. Unfortunately, the parameters found to modulate the magnitude of the shift in our experiments were also found to do the same in the TMS. We regret to not have identified the underlying reason for the shift in the absorption spectrum and hope that the simulation results presented here will be instructive for the Strong Coupling community. This spectral error does not undermine the conclusion of other published studies showing effects of VSC on London dispersion forces.