Applications

Two-dimensional infrared spectroscopy (2DIR) is a nonlinear infrared spectroscopy technique investigating vibrational modes in condensed-phase systems. The technique provides information beyond linear spectra by spreading the vibrational information along multiple axes, which yields a frequency correlation spectrum with information on vibrational mode coupling, as well as chemical and molecular dynamics with femtosecond resolution.

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.

2DIR experiments have become possible with the development of ultrafast lasers, such as PHAROS and CARBIDE, and the ability to generate femtosecond infrared pulses, e.g., using ORPHEUS-MIR broad bandwidth mid-IR source.

Two-dimensional spectroscopy may be also used in the VIS spectral range, where electronic states are investigated; see two-dimensional electronic spectroscopy (2DES).