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Vivek Tiwari

Ph.D. (University of Colorado, Boulder)
B.S. / M.S. (IIT Kanpur)
Assistant Professor
Email: vivektiwari@iisc.ac.in, vtiwari@colorado.edu
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Welcome to MESSR Lab     Multidimensional Electronic Spectroscopy with Spatial Resolution    [‘measure‘]

Multidimensional Femtosecond Spectroscopy coherently excites a manifold of vibronic states, and resolves the ensuing coherent dynamics with conventionally high temporal and spectral resolution. Such information has provided valuable insight into the nature of System and Bath Hamiltonians for a number of systems spanning from proteins, organic photovoltaic polymers, singlet fission materials and perovskites.

Such tools, however, lack the much needed spatial resolution and sensitivity to probe smaller areas and ensembles. Spatially-resolved multidimensional electronic spectroscopy was recently demonstrated to provide ~106 times better spatial resolution and sensitivity than existing multidimensional spectroscopic tools. Such next generation optical techniques can address the emerging challenge in the community of multidimensional spectroscopy – probe smaller spatial and energetic ensembles in order to avoid ‘ensemble dephasing’ effects without sacrificing the information content of a multidimensional spectroscopy experiment. Probing smaller ensembles is necessary to address the open questions regarding the true nature of quantum decoherence in condensed phase, or to extract vibronic splittings arising due to non-Born Oppenheimer intensity borrowing effects.

The broad impetus of our group is to develop improved multidimensional spectroscopic tools to probe matter through controlled interactions with femtosecond pulses, and apply such tools to gain a better understanding of the fundamental physics of energy and charge transfer on femtosecond timescales.

Such tools will allow better probing of fundamental processes ranging from electronic and nuclear interactions among a network of chromophores packed tightly inside a photosynthetic cell, to correlating morphological differences in thin films, well known to dictate device performance of photovoltaic materials, to its effect on the fundamental exciton delocalization physics which occurs on sub-100 fs timescales.

Another major effort of the group will be to understand the above experiments by developing theoretical models of energy and charge transfer in molecular systems. Numerically exact methods which explicitly include non-adiabatic effects such as vibrational-electronic resonance and conical interactions will be employed. Simulations of energy and charge transfer based on such Hamiltonians, and the associated signatures expected in a multidimensional spectroscopy experiment will be integral in analyzing the experimental data.

Representative Publications:

  1. V. Tiwari, Y. A. Matutes, A. T. Gardiner, T. L. C. Jansen, R. J. Cogdell, and J. P. Ogilvie, “Spatially-resolved fluorescence-detected two-dimensional electronic spectroscopy probes varying excitonic structure in photosynthetic bacteria,” Nat. Comm. 9, 4219 (2018). Editors’ Choice
  2. V. Tiwari, Y. A. Matutes, A. Konar, Z. Yu, M. Ptaszek, D. F. Bocian, D. Holten, C. Kirmaier, and J. P. Ogilvie, “Strongly coupled bacteriochlorin dyad studied using phase-modulated fluorescence-detected two-dimensional electronic spectroscopy,” Optics Express 26, 22327-22341 (2018).
  3. V. Tiwari, W. K. Peters, and D. M. Jonas, “Electronic resonance with anticorrelated pigment vibrations drives photosynthetic energy transfer outside the adiabatic framework,” PNAS 110, 1203-1208 (2013). Science Editors’ Choice, PNAS Cover Mention
  4. V. Tiwari, W. K. Peters, and D. M. Jonas, “Vibronic coherence unveiled,” Nat. Chem. 6, 173-175 (2014).
  5. B. Cho*, V. Tiwari*, R. J. Hill, W. K. Peters, T. L. Courtney, A. P. Spencer, and D. M. Jonas, “Absolute Measurement of Femtosecond Pump–Probe Signal Strength,” J. Phys. Chem. A 117, 6332-6345 (2013). (* denotes equal authors)