Electron momentum spectroscopy study of Jahn-Teller effect in cyclopropane

The binding energy spectra of cyclopropane in energy range of 9-19 eV have been measured by the high resolution (e, 2e) spectrometer with 0.5 eV energy resolution. The individual electron momentum distributions for the outer valence orbitals including the two Jahn-Teller splitting components for the highest occupied molecular orbital 3e(') have been obtained. Compared with the results of high level quantum chemistry calculations, the observed different intensities of the experimental momentum profiles for the two Jahn-Teller splitting components have been phenomenologically explained, showing the influences caused by the change in molecular geometry at the instant of ionization from doubly degenerate 3e(') orbital on the electron momentum distributions. In addition, the controversial ordering of the two outer valence orbitals 3a(1)(') and 1a(2)(') has also been assigned unambiguously.