Stephen Leone

Stephen Leone

ProfessorThe John R. Thomas Professor in PhysicsDirector, Chemical Dynamics Beamline, LBNL

Office: 209 Gilman
Main: (510) 643-5467
Other: (510) 486-4754

Research Area(s): Atomic, Molecular and Optical Physics

Biography

Dr. Leone received his B.A. in Chemistry at Northwestern University in 1970 and his Ph.D. in Chemistry at the University of California at Berkeley with Professor C. Bradley Moore in 1974. He was an assistant professor at the University of Southern California from 1974-76. He assumed a position with NIST and the University of Colorado in 1976 and became a full professor in 1982. Dr. Leone was a Fellow and staff member of the National Institute of Standards and Technology, a Fellow of JILA, as well as an Adjoint Professor of Chemistry and Biochemistry and a Lecturer of Physics at the University of Colorado. In 2002, he became Professor of Physics and Chemistry, University of California, Berkeley, director of the chemical dynamics beamline at the Advanced Light Source, Lawrence Berkeley National Laboratory, and John R. Thomas Endowed Chair in Physical Chemistry. He is Director of the Chemical Sciences Division at Lawrence Berkeley National Laboratory. His numerous honors and awards include Fellow, American Physical Society, Optical Society of America, and American Association for the Advancement of Science; Alfred P. Sloan Fellow (1977-81); Department of Commerce Silver Medal Award (1980); American Chemical Society Pure Chemistry Award (1982); American Chemical Society Nobel Laureate Signature Award for Graduate Education in Chemistry, jointly with D.J. Nesbitt and J.T. Hynes (1983); Coblentz Award for Spectroscopy (1984); Department of Commerce Gold Medal Award (1984); Arthur S. Flemming Award for Government Service (1986); Fellowship, Japanese Society for the Promotion of Science (1986); John Simon Guggenheim Fellow (1988); Herbert P. Broida Prize of the American Physical Society (1989); Visiting Miller Research Professor to the University of California, Berkeley (1990); Visiting Professor at the Chemistry Research Promotion Center, Taiwan (1992); Samuel Wesley Stratton Award from the National Institute of Standards and Technology (1992); Bourke Medal of the Faraday Division of the Royal Society of Chemistry (1995); Member of the National Academy of Sciences (1995); Centennial Speaker, American Physical Society (1999); and Fellow of the American Academy of Arts and Sciences (2000); American Chemical Society, Peter Debye Award (2005); Morris Belkin Visiting Professorship, Weizmann Institute (2009); Polanyi Medal of the Gas Kinetics Division of the Royal Society of Chemistry, UK (2010); Miller Professorship, Miller Research Institute (2010); National Security Science and Engineering Faculty Fellowship, Department of Defense (2010); John R. Thomas Endowed Chair in Physical Chemistry, 2010; Irving Langmuir Prize in Chemical Physics, American Physical Society, 2011; Distinguished Schulich Lectureship Award, Technion – Israel Institute of Technology, 2011; Chemical Society Reviews Lecture Award, Royal Society of Chemistry, 2011

Research Interests

Professor Leone's research interests include ultrafast laser investigations and soft x-ray probing of valence and core levels, attosecond physics and chemistry, state-resolved collision processes and kinetics investigations, nanoparticle fluorescence intermittency, aerosol chemistry and dynamics, probing with near field optical microscopy, and neutrals imaging.

Current projects in attosecond physics are described here in more detail and follow along several main themes: Isolated attosecond pulses in the extreme ultraviolet (XUV) region are used in time-resolved spectroscopy of atoms, molecules, and condensed matter. These isolated attosecond pulses are produced by high-order harmonic upconversion in a Ne gas target of a few-cycle near-infrared (NIR) pulse into the XUV spectral region.

A new method of ionization gating allows the generation of energy-tunable isolated attosecond pulses, as opposed to the conventional amplitude gating method, which yields pulses with limited tunability. This increased energy tunability is critical for the application of isolated attosecond pulses to time-resolved spectroscopy. In addition, we have shown that scanning of the carrier-envelope phase allows rapid determination of the contrast ratio of the isolated attosecond pulse. A variety of complementary attosecond spectroscopic techniques are being pursued and developed in the Leone group.

In the first method, initiation of ultrafast dynamics by the XUV isolated attosecond pulse is followed by streak-field detection of the photoelectrons. The dynamics of the various quantum states involved in the time-dependent evolution of the photoexcited state is encoded in the photoelectron spectrum collected as a function of time delay between the XUV pump pulse and the NIR streaking probe pulse. In addition to measuring the photoelectron kinetic energies by linear time-of-flight, photoelectron angular distributions can also be obtained via velocity map imaging. Time-of-flight mass spectrometry is also used to detect photofragments originating from dissociative ionization processes in polyatomics.

In the second method, a few-cycle NIR pulse is used to drive plasmon oscillations in metallic nanostructures, thereby mapping the temporal phase of the oscillation to a kinetic energy modulation of the photoelectrons ejected by the isolated attosecond pulse. This method allows direct observation of plasmon decoherence in real time and paves the way for the rational design of plasmonic nanomaterials. In the third method, photoinitiation of coherent electron dynamics by a few-cycle ultraviolet to NIR pulse is followed by isolated attosecond probing of atomic core level absorptions in atoms and molecules. In addition to transient absorption, transient linear dispersion of a sample can also be measured and yields changes in the real part of the refractive index upon initial photoexcitation. For opaque condensed matter samples, transient reflectivity is employed as an alternative to transient absorption, thereby allowing the study of carrier dynamics in solid state nanomaterials on the attosecond time scale.

Experiments are being explored in confocal microscopy, apertureless near field optical microscopy, and single pulse coherent anti-Stokes Raman microscopy with phase control, and studies involving quantum dot blinking and pump-probe ultrafast studies of semiconductor nanocrystals. Other projects study aerosol light scattering and spectroscopy, aerosol reactions, as well as surface probing of neutrals desorbed by scanning ion microprobes using the chemical dynamics beamline at the Advanced Light Source.

Professor Leone is also available as a research director for the Applied Sciences and Technology (AS&T) Ph.D. program.

Publications

A. A. Cordones, and S. R. Leone, " Mechanisms for charge trapping in single semiconductory nanocrystals probed by fluorescence blinking," Chem. Soc. Rev. (in press) (2012).

S. Chen, M. J. Bell, A. R. Beck, H. Mashiko, M. Wu, A. N. Pfeiffer, M. B. Gaarde, D. M. Neumark, S. R. Leone, and K. J. Schafer, "Light-induced states in attosecont transient absorption spectra of laser-dressed helium, Phys. Rev. A 86, 063408 (2012)..

A. N. Pfeiffer, and S. R. Leone, "Transmission of an isolated attosecond pulse in a strong-field dressed atom," Phys. Rev. A 85, 053422 (2012).

J. S. Prell, L. J. Borja, D. M. Neumark, and S. R. Leone, "Simulation of attosecond-resolved imaging of the plasmon electric field in metallic nanoparticles," Ann. Phys. (Berlin) 1-11, (2012).