Theory predicts UV/vis-to-IR photonic down conversion mediated by excited state vibrational polaritons

This work proposes a photophysical phenomenon whereby ultraviolet/visible (UV/vis) excitation of a molecule involving a Franck-Condon (FC) active vibration yields infrared (IR) emission by strong coupling to an optical cavity. The resulting UV/vis-to-IR photonic down conversion process is mediated by vibrational polaritons in the electronic excited state potential. It is shown that the formation of excited state vibrational polaritons (ESVP) via UV/vis excitation only involve vibrational modes with both a non-zero FC activity and IR activity in the excited state. Density functional theory calculations are used to identify 1-Pyreneacetic acid as a molecule with this property and the dynamics of ESVP are modeled. Overall, this work introduces an avenue of polariton chemistry where excited state dynamics are influenced by the formation of vibrational polaritons. Along with this, the UV/vis-to-IR photonic down conversion is potentially useful in both sensing excited state vibrations and quantum transduction schemes. Vibrational polaritons steer chemical reactions and control quantum states for information processing. Here the authors predict their formation during electronic photo-excitation, enabling a down-conversion of visible to infrared photons.

Automated summary

This study introduces a photophysical phenomenon where UV/vis excitation and a Franck-Condon active vibration of a molecule can lead to IR emission through strong coupling to an optical cavity. The process involves the formation of excited state vibrational polaritons (ESVP) mediated by vibrational modes with both non-zero Franck-Condon activity and IR activity in the excited state. The authors identify 1-pyreneacetic acid as a molecule that exhibits this property and model the dynamics of ESVP. The UV/vis-to-IR photonic down conversion process has applications in sensing excited state vibrations and quantum transduction schemes.