Time-of-flight measurements of single rovibrational states of carbon monoxide

Abstract

A new technique has been developed for the measurement of the translational energy of molecules in single rovibrational quantum states. Molecules from a given rotation–vibration level are excited to a long‐lived electronic state by a pulsed, tunable ultraviolet (UV) laser and are allowed to collide with the surface of a low work function metal. Since the energy of the metastable state exceeds that of the metal’s work function, collisions result in the ejection of electrons from the metal surface, which may be detected with high efficiency. This technique has been applied successfully to the carbon monoxide system, where measurements of molecular beam velocities and extremely weak forbidden electronic transitions have been made. The detection efficiency of this technique is estimated to be 2.0×10⁻⁴, comparable with electron impact ionization and mass‐selected detection. Possible future applications of the technique in spectroscopy, photodissociation, and photon stimulated desorption experiments are discussed.