Two-Dimensional Electronic Spectroscopy
Two-dimensional electronic spectroscopy (2DES) is an ultrafast laser spectroscopy technique that allows studying ultrafast phenomena in condensed-phase systems. The term “electronic” refers to the use of optical frequencies in the visible spectral range to excite the electronic energy states of the system.
This technique records the signal emitted from a system after interaction with a sequence of three laser pulses, typically a few hundred femtoseconds long, provided by PHAROS or CARBIDE femtosecond lasers. This high time resolution allows capturing dynamics within the system that evolve on the same time scale. The main result of this application is a two-dimensional absorption spectrum, showing the correlation between excitation and detection frequencies.
According to Gelžinis et al., the key strengths of 2D spectroscopy include the following:
- The uncoupling of time and excitation frequency resolution allows researchers to follow specific states’ dynamics with selective excitation and excellent time resolution.
- The lack of background signals allows achieving an excellent signal-to-noise ratio.
- A single run of 2D spectroscopy provides information with a wide range of excitation frequencies, while using the pump-probe technique requires many separate measurements.
For the last fifteen years, 2D spectroscopy has contributed heavily to our understanding of excitation dynamics in photosynthetic molecular complexes. It is a safe bet that it will continue to do so for the foreseeable future.
Two-dimensional spectroscopy can also be applied in the IR spectral range, where vibrational states are investigated. See two-dimensional infrared spectroscopy (2DIR).
