Theoretical study of the perturbation parameters in the a 3Π and A 1Π states of CO

Theoretical investigation of the A1Π-X1Σ+, B1Σ+-X1Σ+, C1Σ+-X1Σ+, and E1Π-X1Σ+ transitions of the CO molecule

The spectrum of carbon monoxide is important for astrophysical media, such as planetary atmospheres, interstellar space, exoplanetary and stellar atmospheres; it also important in plasma physics, laser physics and combustion. Interpreting its spectral signature requires a deep and thorough understanding of its absorption and emission properties. A new accurate spectroscopic model for the ground and electronically-excited states of the CO molecule computed at the aug-cc-pV5Z ab initio CASSCF/MRCI+Q level is reported. Detailed investigation of the A1Π-X1Σ+, B1Σ+-X1Σ+, C1Σ+-X1Σ+, and E1Π-X1Σ+ band systems is presented consisting of calculated potential energy curves as well as permanent and transition dipole moment curves. The B1Σ+ and C1Σ+ states are characterized by having multiple avoided crossings which are diabatized to obtain an accurate electronic structure model. The results are validated by comparing our computed spectra with various high-resolution spectroscopy experiments. To the best of our knowledge, this is the first systematic theoretical spectroscopic study of highly excited states of the CO molecule.

Potential curves for the dissociative recombination of CO+

Large scale ab initio calculations are reported for the diabatic (3)Π, (1)Π, (1)Σ(+), (1)Δ, (3)Σ(+), and (3)Δ valence states of CO that provide routes for the dissociative recombination of the ground electronic and vibrational state of CO(+). The most important routes are 2(3)Π, 3(3)Π, 2(1)Π, and D'(1)Σ(+). For electron energies below 0.2961 eV, from the v = 0 ion level, the first two states can generate excited atoms, O((1)D) and C((1)D), but the last two states yield only ground state atoms. From v = 0, hot ground state atoms are generated at 0 eV from each of the four states with C and O having 1.67 and 1.25 eV of kinetic energy, respectively. The potential curves are compared to prior calculations and experiments.

Branching ratio measurements of the predissociation of 12C16O by time-slice velocity-map ion imaging in the energy region from 108,000 to 110,500 cm(-1)

Direct branching ratio measurements of the three lowest dissociation channels of (12)C(16)O that produce C((3)P) + O((3)P), C((1)D) + O((3)P), and C((3)P) + O((1)D) are reported in the vacuum ultraviolet region from 108,000 cm(-1) (92.59 nm) to 110,500 cm(-1) (90.50 nm) using the time-slice velocity-map ion imaging and nonlinear resonant four-wave mixing techniques. Rotationally, resolved carbon ion yield spectra for both (1)Σ(+) and (1)Π bands of CO in this region have been obtained. Our measurements using this technique show that the branching ratio in this energy region, especially the relative percentages of the two spin-forbidden channels, is strongly dependent on the particular electronic and vibrational energy levels of CO that are excited.