CPM Seminar

Coherently-controlled two-dimensional electronic spectroscopy

Valentyn Prokhorenko

Departments of Chemistry and Physics
University of Toronto

Optical two-dimensional photon-echo spectroscopy (2D-PE) is realized with shaped excitation pulses, allowing coherent control of two-dimensional spectra. This development enables probing and manipulating state-selective quantum decoherence and phase (time-) sensitive couplings between states. Designed femtosecond 2D-PE spectrometer with two pulse shapers is based on a passively stabilized four-beam interferometer with diffractive optic, and allows heterodyne detection of signals with long-term phase stability of > Λ/100 in the VIS [1].

First two-dimensional spectra of solvated dye (Rhodamine 101/MeOH), measured with unshaped and shaped pulses, exhibit significant differences [1,2]. In particular, we observe an appearance of fine stucture in the 2D-spectra (at waiting time T = 0) by excitation with the shaped pulses, found to coherently control the population transfer in weak-field limit [2]. By excitation with the phase-shaped pulses we detected an unusually long-lived (T > 40 ps) coherence at room temperatures, induced in weak-field regime.

These experimental findings illustrate direct manipulation of coherence in such complex systems like solvated organic molecules. Some insight into theoretical aspects of coherently-controlled 2D-PE spectroscopy will also be provided.

[1] V.I. Prokhorenko, A. Halpin, and R.J.D. Miller, “Coherently-controlled two-dimensional photon echo electronic spectroscopy,” Opt. Express, 17, 9764—9779 (2009).
[2] A. Paarmann, V.I. Prokhorenko, and R.J.D. Miller,“Diffractive optics based 4-wave, 6-wave... ν-wave nonlinear spectroscopy,” Acc. Chem. Res., 2009 (available online).
[3] V.I. Prokhorenko, A.M. Nagy, and R.J.D. Miller, “Coherent control of the population transfer in complex solvated molecules at weak excitation. An experimental study,&rdquo J. Chem. Phys. 122, 184502—184513 (2005).