Low-Energy Photon and Low-Energy Electron Interactions with Buckminsterfullerene.

Early in the studies of fullerenes, it was discovered that C_{60} exhibited special properties upon interaction with low energy photons and electrons. In many studies of pulsed laser ionization of C_{60}, delayed ionization (ionization occurring musec after energy deposition) was observed. This phenomenon was attributed to a thermionic emission mechanism. The goal of this thesis is to further test the thermionic emission model: (1) A cw argon ion laser was used to ionize C_ {60}. It is found that the ionization is very efficient, and the power dependence of the ion yield is compatible with the thermionic emission model. (2) The external electric field was seen to enhance the ionization efficiency of the C_{60} thermionic emission. In the interaction with low energy electrons, C_{60} is found to capture electrons between 0.15 and 12 eV very efficiently. This thesis represents a careful study using ultra-low energy electron spectroscopy. The results show a 0.15 eV threshold for attachment, as well as other peaks at higher energy. The resonance structures are attributed to electron attachment into the unoccupied electronic states, followed by the release of electronic energy to the vibrational modes of C_sp{60}{-}. Thus a long lived highly-excited C_sp{60 }{-} is formed. An alternative mechanism, termed a "plasmaron", which involves a simultaneous attachment and collective excitation of electrons for C_ {60} is considered for the ~ 5 eV resonance structure. In addition, the lifetimes of the negative ions were measured and compared to the thermionic emission model. The discrepancy is attributed to possible "blackbody like" IR emission which may account for part of the internal energy, resulting in extended lifetimes of the negative ions. In the appendix, a krypton cluster core level excitation experiment is reported using synchrotron radiation from the BNL synchrotron light source. The core level excitation is another technique which provided additional information on the molecular and electronic structures of clusters. In this thesis, krypton clusters spectra are recorded with a multi-channel coincidence technique.