Predissociation rates in carbon monoxide: dependence on rotational state, parity and isotope

Abstract

A high-resolution spectroscopic study of carbon monoxide has been performed using a narrow-band and tunable extreme-ultraviolet laser source in the wavelength range 91–97 nm. For three isotopes 12C 16, 13C 16O and 13C 18O the (4pπ)L 1Π, ν=0, (4 pσ)K 1Σ +, ν=0 and (3sσ)W 1Π, ν=0 states were investigated. The 1Π, ν=2, (3 sσ)W 1Π, ν=2 and (3dπ)L′ 1Π, ν=1 states were studied for 12C 16 and 13C 16O. The 1Π, ν=0 state at 109564.58 cm −1, the (6pσ) 1Σ +, ν=0 state at 109173.68 cm −1, the (5pσ) 1Σ +, ν=0 state at 107174.44 cm −1, and the (4dσ) 1Σ +, ν=0 state at 105676.30 cm −1 were excited only for the main isotope 16C 16O. Previously unknwon states are found at 107365.87 cm −1 ( 1Σ +) for 12C 16O and at 103203.07 cm −1 ( 1Π) for 13C 18O. Indirect evidence is found for a perturber state at 107708±2 cm −2 cm −1 for 12C 16O, while spectroscopic information on the E 1Π, ν=5 state of 13C 18O is deduced from a deperturbation analysis. A rotational-state and isotope-dependent predissociation rate is found for almost all states. A parity dependence is observed for the (4pπ)L 1Π, ν=0 and (3sσ)W 1Π, ν=0 states, where the predissociation rate of the Π e component varies proportional to J( J+1). This effect is attributed a coupling with the repulsive part of the D′ 1Σ + state. Several examples of accidental predissociations have been found, particularly in the (4dσ) 1Σ +, ν=0 state.