Dissociation dynamics of transient species, three-body reaction dynamics, novel mass-spectrometric methods
Ph.D., , University of California, Berkeley
B.A., , Johns Hopkins University
Postdoc, , University of California, Berkeley
Awards and Academic Honors
UCSD Diversity Champion Award
ACS Division of Physical Chemistry Award in Experimental Chemistry
Kurt Shuler Scholar in Physical Chemistry
Fellow, American Physical Society
Alfred P. Sloan Research Fellowship
Camille Dreyfus Teacher-Scholar Award
David and Lucile Packard Fellowship in Sciences and Engineering
Camille and Henry Dreyfus New Faculty Award
Transient species, including reactive free radicals and molecular clusters, play central roles in governing the chemical behavior of complex systems. We seek to characterize these species by using a variety of techniques, including mass spectrometry, photoelectron and photofragment spectroscopies and the measurement of scattering cross-sections. These experiments provide critical tests of modern electronic structure and dynamics calculations, and in the case of three-body dissociation, new types of experimental data on the dynamics of these processes.
Our studies of reactive free-radicals, transition-states and multi-body dissociation dynamics use the photoelectron-photofragment coincidence technique developed here. These experiments are carried out using fast, mass-selected anion beams with short-pulse tunable laser photodetachment. The photoelectron kinetic energy and angle of recoil is measured using imaging techniques, which determines the internal energy in the neutral molecule or cluster under study. If the neutral is unstable and dissociates, then the kinetic energy and angular distributions of the products are recorded using time- and position-sensitive detectors. Analysis of these experiments is carried out in conjunction with ab initio electronic structure, Franck-Condon and dynamics calculations.
One application of these techniques is to the dynamics of hydroxyl radical reactions important in combustion and atmospheric processes. We have also extended this technique to three-body and four-body dissociation processes, respectively, of O3(D2O) and O8. Another important research focus has been reactive organic intermediates such as alkoxides and alkoxy radicals.
Primary Research Area
Atmospheric and Environmental
- New insight into the barrier governing CO2 formation from OH + CO, with C.J. Johnson, B.L.J. Poad and B.B. Shen, J. Chem. Phys. 134, 171106 (2011).
- Photoelectron-photofragment coincidence spectroscopy in a cryogenically cooled electrostatic ion beam trap, with C.J. Johnson, B.B. Shen and B.L.J. Poad, Rev. Sci. Instrum. 82, 105105 (2011).
- The electron affinities, well depths and vibrational spectroscopy of cis- and trans-HOCO, with C.J. Johnson, M.E. Harding, B.L.J. Poad and J.F. Stanton, J. Am. Chem. Soc. 133, 19606 (2011).
- Production of vibrationally excited H2O from charge exchange of H3O+ with cesium, with J.E. Mann, Z. Xie, J.D. Savee and J.M. Bowman, J. Chem. Phys. 130, 041102 (2009)
- Three-body dissociative charge exchange dynamics of sym-triazine, J. Phys. Chem. A 113, 3988 (2009)
- The role of excited-state topology in three-body dissociation of sym-triazine, with J.D. Savee, V. A. Mozhayskiy, J.E. Mann and A.I. Krylov, Science, 321, 826 (2008)
- Alignment of a molecular anion via a shape resonance in near-threshold photodetachment, with Z. Lu, Phys. Rev. Lett. 99, 113005 (2007)
- Three-body dissociation dynamics of the low-lying Rydberg states of H3 and D3, with C.M. Laperle, J.E. Mann and T.G. Clements, Phys. Rev. Lett. 93, 153202 (2004)
- Four-body reaction dynamics: Complete correlated fragment measurement of the dissociative photodetachment dynamics of O8-. With T.G. Clements, Phys. Rev. Lett. 89, 033005 (2002)
- Photoelectron-Multiple-Photofragment-Coincidence Spectrometer. With K.A. Hanold, A.K. Luong, and T.G. Clements. Rev. Sci. Instrum. 70, 2268 (1999)