A new Ultraviolet Magnetic Time-of-Flight Photoelectron Spectrometer (MTOFPES) has been developed for the study of the electronic structure of clusters produced in a pulsed supersonic molecular beam. This is the first technique which has been successful in probing the valence electronic states of metal clusters.
The ultraviolet photoelectron spectra of negative cluster ions of the noble metals have been taken at several different photon energies. These are presented along with the electron affinity and HOMO-LUMO gap measurements for Cu$\sb6\sp-$ to Cu$\sb{41}\sp-$, using 4.66 eV and 6.42 eV detachment energies; Ag$\sb3\sp-$ to Ag$\sb{21}\sp-$, using 6.42 eV detachment energy; and Au$\sb3\sp-$ to Au$\sb{21}\sp-$, using 6.42 eV and 7.89 eV detachment energies. The spectra provide the first detailed probes of the s valence electrons of the noble metal clusters. In addition, the 6.42 eV and 7.89 eV spectra probe the first one to two electron volts of the molecular orbitals of the d valence electrons of copper and gold clusters.
The electron affinity and HOMO-LUMO gap measurements of the noble metal clusters agree with the predictions of the ellipsoidal shell model for mono-valent metal clusters. In particular, cluster numbers 8, 20, and 40--which correspond to the spherical shell closings of this model--have low electron affinities and large HOMO-LUMO gaps.
The spectra of the gold cluster ions indicate that the molecular orbital energies of the cluster valence electrons are more widely spaced for gold than for copper or silver. This is to be expected for the heavy atom clusters when relativistic effects are taken into account.
| Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/16176 |
| Date | January 1988 |
| Creators | Pettiette, Claire Lynn |
| Contributors | Smalley, R. E. |
| Source Sets | Rice University |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | 172 p., application/pdf |
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