New Forms of Infrared Spectroscopy to Probe Metal Containing Clusters in the Gas Phase Michael Duncan University of Georgia Gas phase experiments in the past used lasers to vaporize carbon and produced the unusual "cluster" molecule, C60, which is now known as "Bucky-ball." For this work, Smalley, Kroto and Curl received the Nobel Prize in Chemistry in 1996. Recent new work has shown that unusual clusters also form when metals are combined with carbon. Strongly bound and very stable clusters are produced for titanium carbide and vanadium carbide. Recent work in our labs has investigated the properties of these clusters including the conditions required for their formation, their ionization energies and their photodissociation processes. New experiments in the last year have shown that these clusters are extremely stable and that that they undergo "molecular thermionic emission." This process may be induced via heating with a free-electron laser operating in the IR and far-IR wavelength regions. Ejection of thermionic electrons leaves behind a molecular ion, and this process is strongly enhanced when the infrared laser is tuned to the vibrational spectrum of the cluster. The thermionic emission process then provides a way to measure the IR spectrum of these clusters, via so-called IR-REMPI spectroscopy. This method provides IR spectroscopy for gas phase metal clusters for the first time. Spectra have now been obtained for a variety of metal carbide clusters believed to have different cage and crystalline structures (so-called "met-cars" and "nanocrystals"). These spectra may be compared to the surface phonons of the corresponding bulk materials. In a surprising new twist, the IR spectrum of TiC nanocrystals has been found to match exactly with the previously unidentified emission band found in the spectrum of carbon rich post-AGB stars (known as the "21 micron band"). TiC nanocrystals are thus established for the first time as a seed for interstellar dust formation in these environments. Other new experiments have applied IR-REMPI to study MgO, ZrO2, TiO2 and Al2O3 clusters, demonstrating that this is a new general method with which to probe nanocluster spectroscopy.