Perspective: Two-dimensional resonance Raman spectroscopy

Abstract

Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in complex systems. The 2DRR method can leverage electronic resonance enhancement to selectively probe chromophores embedded in complex environments (e.g., a cofactor in a protein). In addition, correlations between the two dimensions of the 2DRR spectrum reveal information that is not available in traditional Raman techniques. For example, distributions of reactant and product geometries can be correlated in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this perspective article, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide and myoglobin. We also address key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopies. Most notably, it has been shown that these two techniques are subject to a tradeoff between sensitivity to anharmonicity and susceptibility to artifacts. Overall, recent experimental developments and applications of the 2DRR method suggest great potential for the future of the technique. Published by AIP Publishing. [http://dx

Two-Dimensional Impulsively Stimulated Resonant Raman Spectroscopy of Molecular Excited States

“…In real systems, excited-state dynamics often modify this simple scenario, even in the case of the LDHO picture. For example, in the presence of a dynamic shift of the vibrational frequencies due to coupling to a thermal bath, peaks are asymmetrically broadened with respect to the principal diagonal [44,66]. Here, we consider a different situation in which the dynamics are exhausted within the finite duration of the femtosecond pulses.…”

“…In particular, time-domain impulsive stimulated Raman scattering (ISRS) [26][27][28][29][30][31][32][33][34][35][36] offers several advantages over its frequency-domain analogues for the detection of vibronic features, especially for low-frequency modes, by efficiently removing elastic scattering contributions and background noise [37][38][39][40]. Its multidimensional extension, 2D-ISRS, has been theoretically proposed initially [41] and realized in both nonresonant [42,43] and resonant [44,45] implementations to study ground-state intramolecular vibrational anharmonicities, nonlinear corrections to the molecular polarizability, product-reactant correlations, and solvation dynamics, up to the recent realization of single-pulse 2D spectroscopy by means of appropriately shaped light pulses [46], with possible applications theoretically suggested for the x-ray domain [47].…”

Quantum coherence selective 2D Raman–2D electronic spectroscopy

“…GAMERS shares similarities with a set of techniques referred to collectively as 2D Resonance Raman (2DRR) spectroscopy34. The FSRS-like approach to 2DRR (ref.…”

“…GAMERS has several notable differences in information content when compared to related 2DRR techniques34. 2DRR methods employing only resonant excitation pulses generate 2D Raman spectra that, in general, contain both ground and excited electronic state vibrational pathways.…”

Recent advances in multidimensional ultrafast spectroscopy

“…Moran's group have used two different implementations of 2DRS, one where 2D correlation spectra are acquired exclusively in the time domain, and a second which involves a femtosecond-stimulated Raman scattering probe step which is amenable to mixed time-frequency detection [ 189 ]. The particular variant is chosen depending on the Raman frequencies of interest.…”