» Research Group web page		Bruce Hudson  Professor Physical chemistry; biophysical chemistry; quantum chemistry and inelastic neutron scattering applied to molecular solids; fluorescence bshudson@syr.edu phone: 315-443-5805 / fax: 315-443-4070 Office: CST 3-014A Education: • B.S., 1967, California Institute of Technology • Ph.D., 1972, Harvard University • Postgraduate Fellow, 1967-1972, Caltech & Harvard University Honors & Awards: • National Science Foundation Postgraduate Fellowship, 1967-1972 • Alfred P. Sloan Foundation Fellow, 1975-1977 Courses: • CHE 357: Physical Chemistry Laboratory • CHE 436/636*: Advanced Physical Chemistry • CHE 546: Molecular Spectroscopy and Structure   * denotes current Fall '08 course

Research Interests My major current research area involves the application of vibrational inelastic neutron scattering and modern periodic Density Functional Calculations to problems involving the structure and dynamics of molecular crystals. We are also involved in a collaborative research project with the Borer Laboratory involving fluorescence methods and nucleic acid conformational equilibria to detect nucleic acid/protein interactions. Our project includes application of this methodology in drug discovery and environmental detection of pathogens. A recent publication in JACS describes one part of this project.
Neutron scattering is used in a wide variety of applications in studies of liquids and solids. Elastic scattering measured as a function of angle is diffraction and is analogous to x-ray diffraction. A major difference, however, is that neutrons scatter from nuclei while x-rays are scattered by electrons. X-ray scattering increases with the atomic number. The scattering of neutrons, generally speaking, does not vary greatly with atomic number but does depend on the particular isotope involved. The usual use of neutron diffraction in studies of crystalline solids is for the precise location of hydrogen atoms. We have recently begun such studies using neutron powder diffraction studies of polycrystalline samples to obtain precise atomic coordinates for samples at 15 K. These studies are performed at the Argonne National Laboratory near Chicago (www.pns.anl.gov). We are also performing x-ray powder diffraction studies at low temperature at the National Synchrotron Light Source at Brookhaven National Laboratory.
Inelastic neutron scattering (INS) spectroscopy is a technique of vibrational spectroscopy that differs from IR and Raman spectroscopy in several respects. One of these is that there are no selection rules in INS so that many vibrations that are not seen by the optical methods can be observed. The most important and unique feature of INS is that the intensity of vibrational transitions is dominated by motions of the hydrogen atoms in the material. If hydrogen is present it dominates the scattering. For example, methyl rotations, which are very weak in other kinds of spectra, are very strong in INS. All other atoms, including deuterium, do not scatter appreciably by comparison. This permits selective deuteration experiments in which parts of a sample are "removed" by substitution of D for H. Most of our inelastic neutron scattering experiments are performed at the NIST Center for Neutron Research (www.ncnr.nist.gov) or at the ISIS facility of the Rutherford Appleton Laboratory (www.isis.rl.ac.uk) south of Oxford in England. At NCNR we use the spectrometer called FANS while at ISIS we use the spectrometer called TOSCA (www.isis.rl.ac.uk/molecularspectroscopy/tosca/). A collection of INS spectra is available at the TOSCA site. The icosahedral hydrocarbon dodecahedrane, C20H20, is an example of one of our ongoing studies. In a previous study we compared the spectrum computed for this molecule on the basis of an isolated molecule model with the spectrum obtained for the polycrystalline solid. In current work the calculations have been extended to the full periodic solid. The degree of agreement between theory and experiment is now excellent. We are now repeating the determination of the crystal structure of this material using synchrotron radiation and low temperature. It appears that inclusion of the phonon motions in the treatment of the x-ray data is needed in order to obtain a correct C-C bond length for this material. Selected Publications Rivera S.; Hudson, B.S. Rapid exchange luminescence: Nitroxide quenching and implications for sensor applications. J. Am. Chem. Soc. 2006, 128(1), 18-19. DOI: 10.1021/ja0558490 Hudson, B.S.; Allis, D.G.; Parker, S.F.; Ramirez-Cuesta, A.J.; Herman, H.; Prinzbach, H. Infrared, Raman, and Inelastic Neutron Scattering Spectra of Dodecahedrane: an Ih Molecule in Th Site Symmetry. J. Phys. Chem. A. 2005, 109, 3418-3424. DOI: 10.1021/jp0503213 Verdal, N.; Kozlowski, P.M.; Hudson, B.S. Inelastic Neutron Scattering Spectra of Free Base and Zinc Porphines: A Comparison with DFT-Based Vibrational Analysis. J. Phys. Chem. A. 2005, 109, 5724-5733. DOI: 10.1021/jp0507795 Hudson, B.S.; Braden, D.A.; Allis, D.G.; Jenkins, T.; Baronov, S.; Middleton, C.T.; Withnall, R.; Brown, C.M. The crystalline enol of 1,3-cyclohexanedione and its complex with benzene: vibrational spectra, simulation of structure and dynamics and evidence for cooperative hydrogen bonding. J. Phys. Chem. A. 2004, 108(36), 7356-7363. DOI: 10.1021/jp048613b Allis, D.G.; Kosmowski, M.; Hudson, B.S. The Inelastic Neutron Scattering Spectrum of H3B:NH3 and the Reproduction of Its Solid-State Features by Periodic DFT. J. Am. Chem. Soc. 2004, 126(25), 7756-7757. DOI: 10.1021/ja048215m Hudson, B.S. Inelastic neutron scattering: A tool in molecular vibrational spectroscopy and a test of ab initio methods. J. Phys. Chem. A. 2001, 105, 3949-3960. DOI: 10.1021/jp004429o » View all Publications