A STUDY OF THE ABSOLUTE PHOTOABSORPTION, PHOTOIONIZATION AND PHOTODISSOCIATION CROSS-SECTIONS AND THE PHOTOIONIZATION QUANTUM EFFICIENCY OFCARBON-DIOXIDE FROM THE IONIZATION THRESHOLD TO 345-ANGSTROM

The absolute photoabsorption, photoionisation and photodissociation cr oss sections and the photoionisation quantum efficiency of carbon diox ide have been measured using a double ion chamber and monochromated sy nchrotron radiation. In addition to structure associated with well est ablished Rydberg series, some new features have been observed which ar e interpreted in terms of transitions into Rydberg states converging o nto the C-2 Sigma(g)(+) upsilon(1)(+) = 1, upsilon(2)(+) = 0, upsilon( 3)(+)= 1 threshold. The photoionisation quantum efficiency measurement s indicate that the decay of Rydberg states by dissociation into neutr al products is a significant de-excitation route. Rydberg states belon ging to the Henning sharp series are strongly predissociated, whereas autoionisation is the dominant decay mechanism for states associated w ith the Henning diffuse series. The photodissociation cross section is compared to the CO A(1)II --> X(1) Sigma(+) fluorescence spectrum pro duced through photodissociation of CO2, and many similarities are appa rent. A sum rule analysis has been carried out by combining the presen t absolute photoabsorption measurements with similar data covering the remaining wavelength regions.