A study of the absolute photoabsorption, photoionisation and photodissociation cross sections and the photoionisation quantum efficiency of carbon dioxide from the ionisation threshold to 345 Å Original Research Article

The absolute photoabsorption, photoionisation and photodissociation cross sections and the photoionisation quantum efficiency of carbon dioxide have been measured using a double ion chamber and monochromated synchrotron radiation. In addition to structure associated with well established Rydberg series, some new features have been observed which are interpreted in terms of transitions into Rydberg states converging onto the C 2Σg+ ν1+ = 1, ν2+ = 0, ν3+ = 1 threshold. The photoionisation quantum efficiency measurements indicate that the decay of Rydberg states by dissociation into neutral products is a significant de-excitation route. Rydberg states belonging to the Henning sharp series are strongly predissociated, whereas autoionisation is the dominant decay mechanism for states associated with the Henning diffuse series. The photodissociation cross section is compared to the CO A 1π → X 1Σ+ fluorescence spectrum produced through photodissociation of CO2, and many similarities are apparent. A sum rule analysis has been carried out by combining the present absolute photoabsorption measurements with similar data covering the remaining wavelength regions.