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Ultrafast Spectroscopy of Biochemical and Material Systems

The overarching theme of Konar Research Group is to use the modern tools of nonlinear spectroscopy and microscopy to better understand the structure function relationships of biomolecules and novel materials at unprecedented time and length scales. Dynamical processes and interactions with the surrounding bath dictate the molecular function at the microscopic level for (bio)chemical systems. These functions further determine the emergent properties at the macroscopic level. Our group takes an interdisciplinary approach to unravel the dynamical processes and interactions within the system by combining tools from chemistry, physics, optics and biology. In particular, we use the powerful technique of Two Dimensional Electronic Spectroscopy (2DES). This unique technique allows access to the full nonlinear optical response of a physical system by correlating the excitation and detection frequencies. These spectral features and dynamics are obscured in more conventional spectroscopic measurements. For all our techniques, we rely on femtosecond pulses (fs = 10-15 s) which allows us to essentially observe processes occurring from femtoseconds to nanoseconds.

1. Development and Application of Hybrid 2D Spectroscopic Methods

Traditionally, 2D spectroscopy has been implemented in its one color degenerate version in either the UV-visible or mid-IR frequencies. We plan to build upon the existing techniques and apply novel mixed frequency techniques to our problems. In particular, exciting an electronic transition and detecting the resulting changes of a local vibration will provide information on the degree of correlation of the electronic and nuclear dynamics. This technique known as two dimensional electronic vibrational (2DEV) spectroscopy will provide direct access to information that is hard to extract and interpret using the degenerate methods. Alternatively, flipping the pulse sequence will result in vibrational excitation followed by electronic detection or 2DVE spectroscopy which gives access to a complementary set of information. These complementary sets of techniques will be used to shed light on energy and charge transfer processes in natural and artificial photosynthetic systems among other things.

2. Development and Application of 2DUV

Development of CMDS in the UV frequency region has been traditionally slow owing to the challenges in generation of broadband UV pulse and dispersion management. Recent advances in the field have overcome some of these challenges and we plan to further develop and apply CMDS in the UV regime via generation of broadband shaped UV pulses. This technique will be used to investigate molecular conformations of DNA/RNA aggregates in solution which have extremely broad absorption spectra. This information will further help to better elucidate the processes of DNA damage and repair. Larger peptides serving as model for proton coupled electron transfer reactions will also be investigated using this and other hybrid techniques.

We are always on the lookout for interested and motivated graduate and undergraduate students to join our multidisciplinary research team. Please email me or stop by the office to know more about the ongoing projects.

Education
Ph.D., Michigan State University, East Lansing
Postdoc, University of Michigan, Ann Arbor

Expertise
Physical Chemistry, Ultrafast Spectroscopy, Photosynthesis, Energy transfer in condensed phase
 

Selected Publications

1. Y. Song, A. Konar, R. Sechrist, V. P. Roy, R. Duan, J. Dziurgot, V. Policht, K. J. Kubarych and J. P. Ogilvie, “Multispectral Multidimensional Spectrometer Spanning the Ultraviolet to the Mid-Infrared”, Rev. Sci. Inst., 2019, 90, 013108
2. T. E. Wiley, A. Konar, N. A. Miller, K. G. Spears and R. J. Sension, “Primed and Ready for Action: Ultrafast Excited State Dynamics and Optical Manipulation of a Four Stage Rotary Molecular Motor”, J. Phys. Chem. A, 2018, 122, 7548
3. A. Konar, R. Sechrist, Y. Song, V. Policht, P. D. Laible, D. F. Bocian, D. Holten, C. Kirmaier and J. P. Ogilvie, “Electronic Interactions in the Bacterial Reaction Center revealed by Two-Color 2D Electronic Spectroscopy”, J. Phys. Chem. Lett., 2018, 9, 5219
4. A. Niedringhaus, V. R. Policht, R. Sechrist, A. Konar, P. D. Laible, D. F. Bocian, D. Holten, C. Kirmaier and J. P. Ogilvie “Energy Transfer and Charge Separation in the Bacterial Reaction Center Probed by Two Dimensional Electronic Spectroscopy”, Proc. Natl. Acad. Sci., 2018, 115, 3653.
5. A. Konar, Y. Shu, V. V. Lozovoy, J. E. Jackson, B. G. Levine and M. Dantus, “Polyatomic Molecules under Intense Femtosecond Laser Irradiation”, J. Phys. Chem. A, 2014, 118, 11433
6. A. Konar, V. V. Lozovoy and M. Dantus, “Solvent Environment Revealed by Positively Chirped Pulses”, J. Phys. Chem. Lett., 2014, 5, 924.