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

Abstract

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.

Surface-Enhanced Infrared Absorption Spectroscopy by Resonant Vibrational Coupling with Plasmonic Metal Oxide Nanocrystals

“…Infrared absorption spectra serve as fingerprints to identify molecules and their organization, playing a central role in applications including biomarker detection, waste identification, pollutant monitoring, and the identification of molecular structures and interactions . Molecular vibrational modes also provide insights into the nature of chemical bonds, with connections to the potential energy surfaces for chemical reactions and vibrationally coupled electronic transitions . But, molecular vibrations have inherently weak oscillator strength.…”

“…4 Molecular vibrational modes also provide insights into the nature of chemical bonds, with connections to the potential energy surfaces for chemical reactions 5 and vibrationally coupled electronic transitions. 6 But, molecular vibrations have inherently weak oscillator strength. So, to increase sensitivity and lower the detection limit, strategies for enhancing vibrational signals are needed.…”