Applications

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 fact that the optical frequencies in the visible spectral range are used to excite the electronic energy states of the system.

This technique records the signal emitted from a system after an interaction with a sequence of three laser pulses. Such pulses usually have a time duration of a few hundred femtoseconds, provided by PHAROS or CARBIDE femtosecond lasers. This high time resolution allows capturing of dynamics inside the system that evolves with the same time scale. The main result of this application is a two-dimensional absorption spectrum that shows the correlation between excitation and detection frequencies.

According to Gelžinis et al., the key strengths of 2D spectroscopy are the following. First, the uncoupling of time and excitation frequency resolution allows the researchers to follow specific states’ dynamics with selective excitation and excellent time resolution. Second, the lack of background signals means that an excellent signal-to-noise ratio can be achieved. Third, a single run of 2D spectroscopy provides information with a wide range of excitation frequencies while using the pump-probe technique that requires many separate measurements. All things considered, 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 may be also used in the IR spectral range, where vibrational states are investigated; see two-dimensional infrared spectroscopy (2DIR).