Graduate Study in - Chemistry - Johns Hopkins University

Paul J. Dagdigian
Experimental Physical Chemistry
Gas-Phase Collision Dynamics and Spectroscopy
pjdagdigian@jhu.edu
Ph. D., University of
Chicago
Postdoctoral, Columbia
University
Fellow, American Physical
Society
We are employing laser fluorescence excitation and resonance-enhanced
multiphoton ionization of atoms and small molecules in studies of
gas-phase collisional processes, involving chemical reactions,
photodissociation, and nonreactive energy transfer processes. Recent
work has included the study of collision-induced rotational and
electronic transitions in the CN radical and the photodissociation of vibrationally
excited methyl chloride.
We are also interested in understanding the non-bonding interactions
between light atoms, such as boron, carbon, aluminum, and silicon, with rare gases
and small molecules such as H 2 . We interrogate these interactions through the
measurement of the electronic spectra of weakly bound complexes of these species,
prepared in a free-jet supersonic expansion. Such studies allow us to infer the
evolution of the chromophore of an atomic transition from that in the free atom,
binary and higher complexes through to the atom-doped solid.
There is a continuing need for the development of laser diagnostics for the
detection of transient species in reactive environments, as well as the detection of
explosives in trace quantities. Our group is participating in a recently funded DoD
multi-university initiative, “Spectroscopic and Time Domain Detection of Trace
Explosives in Condensed and Vapor Phases.” We will be implementing cavity
ring-down spectroscopy (CRDS) as one of a suite of ultrasensitive laser analytical
techniques to be applied to the detection of land mines. In our laboratory, we are also
employing CRDS to study the spectroscopy and kinetics of transient intermediates,
for example the H 2 CN radical.
Selected Publications include:
Tan, X.; Dagdigian, P. J.; and Alexander, M. H., “Electronic Spectroscopy and Excited State Dynamics of the Al–H 2 /D 2 Complex,”
Faraday Discuss. 2001, 118, 387.
Lei, J.; and Dagdigian, P. J., “Laser Fluorescence Excitation Spectroscopy of the CAr van der Waals Complex,” J. Chem. Phys.
2000, 113, 602.
Lei, J.; Teslja, A.; Nizamov, B.; and Dagdigian, P. J., “Free-Jet Electronic Spectroscopy of the PO 2 Radical,” J. Phys. Chem. A 2001,
105, 7828.
Nizamov, B.; Dagdigian, P. J.; and Alexander, M. H., “State-Resolved Rotationally Inelastic Collisions of Highly Rotationally Excited
CN(A 2 ∏) with Helium: Influence of the Interaction Potential,” J. Chem. Phys. 2001, 115, 8393.
8 Graduate Study in Chemistry at The Johns Hopkins University