Transporting and concentrating vibrational energy to promote isomerization.

Visible-light absorption and transport of the resultant electronic excitations to a reaction centre through Förster resonance energy transfer (FRET) are critical to the operation of biological light-harvesting systems, and are used in various artificial systems made of synthetic dyes, polymers or nanodots. The fundamental equations describing FRET are similar to those describing vibration-to-vibration (V-V) energy transfer, and suggest that transport and localization of vibrational energy should, in principle, also be possible. Although it is known that vibrational excitation can promote reactions, transporting and concentrating vibrational energy has not yet been reported. We have recently demonstrated orientational isomerization enabled by vibrational energy pooling in a CO adsorbate layer on a NaCl(100) surface. Here we build on that work to show that the isomerization reaction proceeds more efficiently with a thick CO overlayer that absorbs more mid-infrared photons and transports the resultant vibrational excitations by V-V energy transfer to a CO-NaCl interface. The vibrational energy density achieved at the interface is 30 times higher than that obtained with direct excitation of the interfacial CO. We anticipate that with careful system design, these concepts could be used to drive other chemical transformations, providing new approaches to condensed phase chemistry.