Condensed Phase Dynamics Group
Experimental techniques
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Apart from using several routine steady-state and time-resolved optical spectroscopic techniques, for example, fluorescence lifetime measurement by time-correlated single-photon counting (TCSPC), we are developing the following cutting-edge techniques:
Two-dimensional electronic spectroscopy (2DES):
2DES is a third order nonlinear optical spectroscopy that has enabled us recording time-resolved correlation spectra between absorption and emission frequencies. Analogous to 2D-NMR spectroscopy 2D-CS disentangles population and coherence dynamics, but with unprecedented time resolution compared with 2D-NMR; this makes 2DES superior to any (linear and) 1D third-order nonlinear optical spectroscopic tool (for example, femtosecond pump/probe spectroscopy).
We want to study ultrafast energy transfer dynamics within photovoltaic materials by 2DES using a visible femtosecond pulse-shaper. We are also interested in theoretical investigation of various aspects of energy transfer in these artificial analogs.
Read more about 2DES: Conceptual understanding of 2DES
Time-Resolved Spectrally Dispersed Impulsive Stimulated Raman Spectroscopy is a fifth order time-domain Raman spectroscopy to map out the complex PES of the excited-states. It involves a photopump to create population in electronically excited state and recording the temporal evolution of vibrational wavepacket as the photoreaction proceeds.
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We want to study the structural dynamics upon photoswitching/photoactivation in fluorescent proteins. We would like to explore how such slow processes affect the ultrafast processes in these systems.
Time-Resolved Spectrally Dispersed Impulsive Stimulated Raman Spectroscopy:
Optical tweezers are single beam gradientoptical trap that makes use of a tightly focused laser beam having a transverse Gaussian intensity profile. It was shown that high repetition-rate ultrafast pulsed excitation can efficiently trap 100nm latex nano-particles.
We want to develop a femtosecond optical tweezer for direct trapping and manipulation of individual molecules.