Observation of the electronic energy transfer reaction CO(a3Π) + NO(X 2Π) → CO(X 1Σ+) + NO(a 4Π) in molecular beams

Metastable CO(a 3Π) molecules in a molecular beam were allowed to interact with ground-state NO molecules under single collision conditions. Optical emission from the collision region was spectrally analyzed at a resolution of 1.5 Å FWHM. In the wavelength range 290–400 nm, NO β bands having an anomalous contour were observed. Superimposed on a broad intensity distribution were pairs of narrow “spikes”. The broadband emission is due to NO(B) formed by energy transfer from CO(a) to NO(X). The line emission is evidence of another reaction branch, giving NO(a) products. Only those NO(a) molecules can emit which originate in specific “gateway” levels, exhibiting some NO(B) character as a result of S/O perturbation. The gateway emission was filtered out of the broadband background utilizing magnetic field quenching.