MOLECULAR-BEAM STUDY OF THE COLLISION-INDUCED INTRAMOLECULAR ENERGY-TRANSFER CO(A(3)PI-]A('3)SIGMA(+), D(3)DELTA)

The collision-induced intramolecular energy transfer from CO(a(3) Pi) to CO(a'(3) Sigma(+)) and CO(d(3) Delta) was studied under single-coll ision conditions in a beam/gas-cell arrangement. CO molecules were exc ited into the long-lived a(3) Pi state in a de discharge burning in th e expansion region of the CO(X) supersonic beam. The relative vibratio nal distribution of CO(a(3) Pi) was obtained from the spontaneous beam afterglow (AG) emission spectrum of the CO(a --> X) Cameron bands. Ad ditional emission of the CO(a'3 Sigma(+)) and CO(d(3) Delta) states wa s observed to result from collisions with a target gas (He, Ne, Ar, Kr , and Xe) in a cell. This collision-induced afterglow (CIAG) is due to near-resonant intramolecular energy transfer CO(a --> a', d). From th e CIAG spectra absolute state-to-state cross sections for populating v arious vibrational states in both CO(a') and CO(d) were deduced. They were obtained by normalizing the emission intensities of the product C O(a') and CO(d) levels to those of the CO(a) reactant levels. Spectral overlaps of the d(3) Delta and a'(3) Sigma(+) emissions were deconvol uted by means of computer simulation. The role of the energy gap betwe en the reactant and the product states in the intramolecular transfer processes is discussed. The CO(d,upsilon=2) level is populated to a la rge extent via perturbations with the CO(a,upsilon(a)=9) level, accord ing to the gateway mechanism. As a result, the emission from this part icular level exhibits a very irregular band contour, with intense supe rimposed spikes marking the perturbed rotational states.