Photoabsorption processes in nitrous oxide and formaldehyde

Absorption oscillator strengths and photoionization. cross sections for ele ctronic transitions involving Rydberg states that are relevant to the photo chemistry of N2O and H2CO are reported. These compounds have been found to play an important role in the evolution of Earth's upper atmosphere. Howeve r, the difficulties encoutered in both laboratory measurements and theoreti cal calculations on the photoabsorption of these compounds are responsible for the scarcity of data in the literature. The present calculations have b een performed with the molecular-adapted quantum defect orbital (MQDO) meth od, of which the adequacy for this type of studies has recently been assess ed. A comparative analysis of the photoabsorption intensities in the molecu les and their constituting atoms has enabled us to predict the variation of the extent of atomic character of the molecular Rydberg orbitals with the degree of excitation. (C) 2001 John Wiley & Sons, Inc.