Observation of an isomerizing double-well quantum system in the condensed phase

Upside-down molecules on a salt surface The quantum states of molecules are usually measured in gas-phase studies to minimize collisions that would blur the spectra. However, for carbon monoxide (CO) molecules adsorbed on a NaCl(100) surface, infrared emission from even high vibrational states can be resolved. In quantum-state resolved spectra, Lau et al. found that infrared-laser excitation of a monolayer of CO adsorbed on NaCl(100) forms an isomer in which CO binds to Na + through its O atom in an upside-down configuration (see the Perspective by Wu). These results could be understood with a simple vibrationally adiabatic electrostatic theory, making this system convenient for studies of the isomerization chemistry. Science , this issue p. 175 ; see also p. 148