People

The majority of interesting reactions from a biological, environmental, or engineering perspective, occur in fluid condensed phase environments. In such an environment a chemical reaction is controlled by intermolecular interactions with surrounding solvent bath as well as by the intramolecular Hamiltonian. Interaction with the solvent often results in a situation where reactions are controlled by the competition between intermolecular and intramolecular energy relaxation on the time scales ranging from femtoseconds to picoseconds. The goals of our research program are three fold:

(1) To develop a detailed understanding of the fundamental processes which govern chemical reaction dynamics in fluid environments.

(2) To use sculpted light pulses to control reactions in condensed phases.

(3) To use short light pulses to establish synchronization and study enzyme mechanism in complicated biological systems.

2. Biophysics

3. Coherent Control

References:
Carroll, E. C., Pearson, B. J., Florean, A. C., Bucksbaum, P. H., and Sension, R. J., 2006, "Spectral phase effects on nonlinear resonant photochemistry of 1,3-cyclohexadiene
in solution" The Journal of Chemical Physics, v124 (11) 114506

Research area keywords: Theoretical and Computational Chemistry

Understanding dynamics, chemical reactivity and spectroscopy in condensed matter is at the forefront of modern physical chemistry. Recent experimental advances have made it possible to explore and control dynamics on an ultrafast time-scale, and to probe individual molecules embedded deep inside condensed phase hosts (crystals, liquids, glasses, proteins, etc.). The unprecedented level of detail made available by these experiments calls for the development of new theoretical models and computational methodologies, which is exactly what we do! Current research projects in the Geva group include:

(1) Quantum dynamics and spectroscopy in condensed phase. We develop methods for computer simulation of classically-forbidden processes that take place in solution. Our methods are based on path-integral and master equation approaches for describing the quantum mechanics of many-body systems. The development of such methods is indispensable for the understanding of ultrafast spectroscopy experiments, vibrational and electronic relaxation, as well as electron and proton transfer, which lie at the heat of many important chemical and biological systems.

(2) Coherent control in condensed phase. Recent advances have made it possible to design laser pulses that can optimize the outcome of molecular processes (e.g., maximize the yield of an unfavorable product of a chemical reaction). The next challenge in this field would involve achieving such control in solution. We develop theoretical methods and computer simulation techniques for understanding the interplay between coherent control and dissipation, and the prospects of controlling dissipation by coherent control. This project is part of the interdisciplinary program of a NSF-funded Physics Frontier Center, and involves collaborations with experimental groups in the Chemistry and Physics departments at UM.

(3) Single molecule spectroscopy in biosystems. Understanding the conformational dynamics of biomolecules, such as protein folding, is of fundamental and practical importance. It has recently become possible to perform spectroscopic measurements on individual biomolecules, such as proteins, DNA and RNA molecules. Our goal is to understand the relationship between these measurements and the underlying conformational dynamics. Our approach is based on stochastic models and dynamical simulations of simple model biomolecules, and puts emphasis on correlations between structure and dynamics.

Project:
Protein structure and dynamics from single-molecule uorescence-resonance energy transfer

References:
Ka, B.J. and Geva, E. (2006), “A nonperturbative calculation of nonlinear spectroscopic signals in liquid solution”, J. Chem. Phys. 125, 214501

Ka, B.J.,  Zhang M-L and Geva, E. (2006), “Homogeneity and Markovity of electronic dephasing in liquid solutions”, J. Chem. Phys. 125, 124509

Zhang M-L., Ka, B.J. and Geva, E. (2006), “Nonequilibrium quantum dynamics in the condensed phase via the generalized quantum master equation”, J. Chem. Phys. 125, 044106

Our research is at the intersection of Chemistry, Physics and Biology. We ask questions that will help us to learn the basic design and functional principles behind the structure and function of biological molecules. Ultimately we would like to know why nature has chosen to shape her structures the way she has. "Why" questions, however, are very difficult to address, so we will begin by investigating how proteins work, how they interact with their surroundings, and how they interact with other proteins. This understanding would put us in a very powerful position to design, alter and manipulate chemical structure and reactivity in a rational way. Embedded within a broader context of structural biology, we might see the day where drug design and bioengineering are truly based on microscopic molecular foundations. Our group uses different kinds of ultrafast, nonlinear optical spectroscopy to follow biological molecular dynamics. The basic driving force is to develop a bond-by-bond view of real-time motion in these wonderfully complex, mesoscopic systems.

Project:
1. Multidimensional Infrared Spectroscopy

2. Ultrafast Dynamics of Proteins

References:
M. J. Nee, R. McCanne, K. J. Kubarych, M. Joffre, Two-dimensional infrared spectroscopy detected by chirped pulse upconversion, Opt. Lett. 32 (2007) 713-715.

Project:
1. Protein-Mediated DNA Looping

2. Constant Force Optical Tweezers and DNA Dynamics

References:
Seth Blumberg, Alexei V. Tkachenko, and Jens-Christian Meiners, Disruption of Protein-Mediated DNA Looping by Tension in the Substrate DNA, Biophys. J. 2005 88: 1692-1701

Project:
1. Nonlinear Microscopy

2. Two Dimensional Electronic Spectroscopy

References:
J. P. Ogilvie, E. Beaurepaire, A. Alexandrou, M. Joffre, Fourier transform coherent anti-Stokes Raman scattering microscopy, Optics Letters, (2006) 31, 4, 480-482.

Others Publications

Professor Chupp and his group pursue a program that uses precision measurement techniques and symmetry principles in particle physics investigations and applies the technology developed for those investigations to a variety of endeavors. The primary current efforts use polarized cold neutron beams and rare isotopes. The hadronic weak interaction is being studied in the n+p > d+gamma experiment currently at Los Alamos. Neutron beta-decay provides a probe of new physics that manifests time-reversal violation in the emiT experiment, which recently completed running at NIST. The new Fundamental neutron Physics Beamline at the SNS at Oak Ridge will provide a new generation of high precision experiments including n +p > d+gamma, PANDA, the Proton Asymmetry in Neutron Decay experiment, and abBA, a global set of neutron decay correlation measurements. Time revesal invariance violation is also manifest in the permanent electric dipole moments (EDMs) induced in atoms by elementary particle interactions beyond the Standard Model. Rare isotopes, e.g. 223-Rn, are used because large enhancements of time- reversal violating effects are expected due to octupole deformation of the nucleus. Experiment E-929 at TRIUMF will measure the EDM of 223-Rn. The Rare Isotope Accelerator, RIA, will produce much greater quantities of 223-Rn and provide for more precise measurements. We also continue to work on applications of laser polarized 129-Xe to medical imaging.

Project:
1. Applications of laser polarized xenon to biology and medicine
2. Radon-EDM experiment
3. Neutron decay and PANDA

References:
E. R. Tardiff, J. A. Behr, T. E. Chupp, K. Gulyuz, R. S. Lefferts, W. Lorenzon, S. R. Nuss-Warren, M. R. Pearson, N. Pietralla, G. Rainovski, J. F. Sell, G. D. Sprouse,Polarization and relaxation of radon

Our Research group utilizes a number of spectroscopic techniques towards investigating the optical properties and applications of novel organic macromolecular materials. A major emphasis is placed on the new properties observed in organic macromolecules with branching repeat structures as well as organic macromolecules encapsulated with small metal particles. These materials have been suggested to be candidates for variety of applications involving light emitting devices, artificial light harvesting, strong optical limiters, enhanced nonlinear optical effects, quantum optical effects and as sensors in certain organic and biological devices.

Project:

References:

Ultracold gases have a broad range of applications, including atom interferometry, metrology, and quantum information science. Moreover, these gases form a quantum many-body system with tunable interactions that can emulate various condensed matter phenomena. In addition to exploring these topics, Professor Leanhardt plans to use ultracold gases to probe fundamental questions of nature, such as the strength of gravity at short length scales and the possibility of symmetry violation in the form of permanent electric dipole moments. These low energy, laboratory-based experiments test elementary particle theories (such as Supersymmetry) at the TeV energy scale and provide complementary data to high energy, collider-based experiments at Fermilab and CERN.

Project:
Yb Laser Cooling and Trapping

References:

Professor Raithel employs laser-cooling technology to study the quantum dynamics of cold atoms under various interesting conditions. Cold atoms can be trapped in optical lattices, which are periodic light-shift potentials generated by multiple interfering laser beams. In Raithel's laboratory, the research group investigates the tunnel effect in optical lattices and its modification due to geometrical lattice potentials. Their research also includes wave-packet dynamics, decoherence and quantum-classical feedback circuits. Professor Raithel further studies cold Rydberg-atom gases and cold plasmas in weak and strong magnetic fields. This area has potential applications in quantum information processing. Professor Raithel also researches on phase- and amplitude-stable continuous-wave atom lasers and on the interaction between Bose-Einstein condensates with ultra-cold impurity particles.

Project:
1. Optical Lattices

2. Cold Rydberg Atoms and Plasmas

3. Dipole Blockade

4. Atom Laser and BEC

References:
R. Zhang, R. E. Sapiro, N. V. Morrow, G. Raithel, Transition of laser cooling between standard and Raman optical lattices, Phys. Rev. A 74, 33404 (2006).

The research program in my group utilizes laser cooling and trapping of atoms to study a wide range of fundamental problems at the boundary between atomic physics and condensed matter physics. We now have two working Bose-Einstein condensates, one in rubidium and the other in sodium. These tools will be applied to study problems in quantum chaos, quantum transport in optical lattices, and quantum computing. We are also building a new project in atomic interferometry with slow ground-state helium and neon atoms for fundamental tests of quantum mechanics and atom-surface interaction.

Project:

References: