Rotationally resolved photoionization dynamics of hot CO fragmented from OCS

The photoionizationdynamics of rotationally hot CO, photodissociated from OCS, have been studied using laser photoelectron spectroscopy via the intermediate B^1Σ^+Rydberg state leading to the X^2Σ^+ of the ion. The photodissociation of OCS near 230 nm produces rotationally hot, but vibrationally cold CO (X^1Σ^+,N″,v″=0,1) fragments along with S (^1D) atoms. These high rotational levels show photoelectron spectra with a very strong ΔN=0 transition and weaker ΔN=±1, ±2, and ±3 transitions. Agreement between measured and calculated spectra is good and suggests that there is significant angular momentum coupling in the photoelectron orbital. In the ionization step not only Δv=0, but also off-diagonal, non-Franck–Condon (Δv≠0) transitions are observed. The intensities of these transitions vary strongly within the region studied and can be explained by the excitation of superexcited Rydberg states with an A^2Π core.