The spectroscopy of the geminal ethylene difluoride (1,1-C sub(2)H sub(2)F sub(2)): the HeI, threshold and constant ion state photoelectron spectroscopies

The threshold photoelectron spectrum (TPES) and the constant ion state (CIS) spectra of the individual ionic states of 1,1-C sub(2)H sub(2)F sub(2) have been recorded using synchrotron radiation. The TPES has been measured between 9.5 and 28 eV photon energy. For comparison, the Hel photoelectron spectrum (HeI-PES) has also been measured and analysed in detail. Numerous vibrational structures, reported for the first time, observed in the ground state and the seven excited states of the cation are analysed. Quantum chemical calculations have been performed and provided support to the assignments. The exceptional contribution of autoionization to the Hel-PES could be emphasized. State-selected CIS spectra highlighted the importance of the autoionizing contribution to the production of almost all ionized states of 1.1-C sub(2)H sub(2)F sub(2) observed in this work. Several peculiarities of the vibrationally resolved CIS spectra are analysed.