VU Physics and Astronomy Colloquium

Friday, September 26, 2008. Join us in NSC 231 at 3:05 for refreshments. Talks start at 3:20 in NSC 224.

Student Summer Research

"Examining Multiplicity in the Rate Determining Step of Vanadium Oxide Catalysis"

Dan Brandt

The rate-determining step of the oxidative dehydrogenation of propane on vanadium oxide structures in both the gas phase and with a titania supported monomer structure was investigated in detail with intent of locating a spin crossing. The spin crossing was found to occur at approximately 1.1 Å OH distance in the gas phase and at an energy of approximately 48 kcal/mol relative to the singlet reactants. With a TiO2 support, the distance was found to be 1.125 Å OH distance and the energy was 43 kcal/mol. Additionally, single point energy calculations were computed as a measure of accuracy for these partial optimizations. These calculations and the impact of f-functions on the basis set are also discussed.

"An Energy Calibration of the FN Tandem Accelerator Magnet Analyzing System at Notre Dame"

Ansel Hillmer

This work established the groundwork for a proper calibration of the magnet analyzing system for the FN Tandem accelerator at the University of Notre Dame. The calibration utilized (p.n) reactions with well-known threshold energies to correlate NMR Frequency with beam energy. A neutron detector composed of three 3He proportional counters with moderating polyethylene has been constructed to detect the neutrons. To maximize detection efficiency, GEANT4 was employed to determine the optimal dimensions of the moderator. The maximum efficiency was found to occur with a 3-inch moderator half-length, with the efficiency varying by 2.2% over an 11keV proton beam energy range. A preliminary analysis of data from the 27Al(p,n)27Si yields a result of 5.803MeV corresponding to a frequency of 14.64±.01MHz.