AN EXPERIMENTAL AND THEORETICAL-STUDY OF THE VALENCE SHELL PHOTOELECTRON-SPECTRUM OF ALLENE

The photoelectron spectrum of allene has been studied using He I, He I I and synchrotron radiation as sources for ionisation. In addition to the main bands associated with the single hole states, a complex satel lite structure due to many-electron effects has been observed in both the outer and inner valence regions. Two variations of the many-body G reen's function technique have been employed to determine the ionisati on energies and pole strengths for all valence states, and the results have facilitated the interpretation of the experimental spectra. Phot oelectron angular distributions and photoionisation branching ratios h ave been measured using monochromated synchrotron radiation in the 15- 120 eV range. He I and He II excitation have been used to obtain highl y resolved spectra, and vibrational structure has been studied in the X (2)E, A (2)E and B (2)A, ionic states. Excitations of Jahn-Teller ac tive modes have been found to be important in the X 2E and the A (2)E states.