Figure 1: Model 2D spectrum for a three-component system. The elongation of the peaks along the diagonal displays the instantaneous distribution of frequencies in the transition, whereas the minor axes of the elliptically shaped diagonal peaks are measures of the homogeneous linewidths.
Two-dimensional electronic spectroscopy (2DES) is the optical analogue of Nuclear Magnetic Resonance, a spectroscopic technique that has revolutionized structural biology, enabling the determination of complex molecular structures with high spatial resolution.
2DES is the “ultimate” time-resolved nonlinear optical experiment, since it provides the maximum amount of information about the third-order nonlinear response of a system, and any other third-order nonlinear spectroscopy (such as pump-probe) is contained in the 2D spectrum.
2DES displays its full power in systems with multiple interacting components. 2DES provides two dimensional spectra that shows correlations between excitation and detection frequencies, with simultaneously high spectral and temporal resolution.
2DES can dissect congested spectra and reveal the molecular connections between transitions, thus providing a means to elucidate the overall functionality of a sample.
Two-dimensional electronic spectroscopy requires the interaction of the sample with a sequence of 3 laser pulses. Two of them must be phase-locked replicas, with variable delay, and can be easily generated with NIREOS’ GEMINI-2D interferometer by placing it in the pump beam before the sample, thus turning a pump-probe setup into a state-of-the-art 2DES spectrometer.
Figure 2: Pulse sequence in a 2DES experiment. In a 2-colour experiment pulses 1-2 (interferometrically stable) can have a different color with respect to pulses 3/LO (also interferometrically stable).
NIREOS’ GEMINI-2D is employed to generate pulses 1 and 2 and control their coherence time τ.
Oscillating transient signal as a function of the relative delay T1 between the two pump pulses at a selected probe wavelength and at a fixed population time T2.
A Fourier Transform ad a function of T1 for each probe wavelength allows one to retrieve the 2D maps ad a function of detection and excitation wavelengths.
Bidimensional maps of 2D Electronic Spectroscopy measurements obtained on a Light Harvesting (LH1) complexo f a sample of Rhodospirillum Rubrum for three diferente populations time T2 (15 fs, 45 fs, 4000 fs).
