Two-dimensional electronic–vibrational spectroscopy: Exploring the interplay of electrons and nuclei in excited state molecular dynamics

Abstract

Two-dimensional electronic-vibrational spectroscopy (2DEVS) is an emerging spectroscopic technique which exploits two different frequency ranges for the excitation (visible) and detection (infrared) axes of a 2D spectrum. In contrast to degenerate 2D techniques, such as 2D electronic or 2D infrared spectroscopy, the spectral features of a 2DEV spectrum report cross correlations between fluctuating electronic and vibrational energy gaps rather than autocorrelations as in the degenerate spectroscopies. The center line slope of the spectral features reports on this cross correlation function directly and can reveal specific electronic-vibrational couplings and rapid changes in the electronic structure, for example. The involvement of the two types of transition moments, visible and infrared, makes 2DEVS very sensitive to electronic and vibronic mixing. 2DEV spectra also feature improved spectral resolution, making the method valuable for unraveling the highly congested spectra of molecular complexes. The unique features of 2DEVS are illustrated in this paper with specific examples and their origin described at an intuitive level with references to formal derivations provided. Although early in its development and far from fully explored, 2DEVS has already proven to be a valuable addition to the tool box of ultrafast nonlinear optical spectroscopy and is of promising potential in future efforts to explore the intricate connection between electronic and vibrational nuclear degrees of freedom in energy and charge transport applications.

The initial charge separation step in oxygenic photosynthesis

“…A detailed description of the experimental setup of 2DEV spectroscopy can be found elsewhere 43 , 48 . Briefly, the output of a Ti:sapphire oscillator (Vitara-S, Coherent) was regeneratively amplified with a 1 kHz repetition rate (Legend Elite, Coherent), an energy of 1 mJ/pulse, and a pulse duration of 40 fs.…”

“…Compared to the previously mentioned techniques, the emerging method of two-dimensional electronic-vibrational (2DEV) spectroscopy, which correlates electronic excitation and mid-IR detection 43 – 48 , has the potential to overcome the challenges associated with congested electronic spectra. In particular, the simultaneous spectral resolution along both the visible excitation and IR detection axis has been shown to enable the clear assignment of transient species 44 – 48 . In this study, we investigated the excited state dynamics of the PSII-RC via 2DEV spectroscopy.…”

Connecting the Dots for Fundamental Understanding of Structure-Photophysics-Property Relationships of COFs, MOFs, and Perovskites using a Multiparticle Holstein Formalism

“…[129][130][131][132][133][134][135][136][137][138][139][140][141][142][143][144] These vibronic effects, which arise from the coupling of electronic transitions with the nuclear vibrational motion, play a central role in determining the photophysical response of organic 145,[145][146][147] and hybrid materials [148][149][150][151][152][153][154] as well as excited state dynamics in chemical and biological systems. [155][156][157][158][159][160][161][161][162][163] It is therefore not surprising that any progress in the design of novel materials warrants a robust theoretical methodology that can provide an in-depth understanding of how the complicated interplay between photons, excitons, polarons, bipolarons, phonons, and spins influences the photoinduced excited state processes of a wide range of materials. Despite significant recent progress, two main challenges still persist which involve a quantitative understanding of how electron-phonon coupling and defects influence the electronic, optical, and transport properties of functional electronic materials.…”

Spin–Orbit Natural Transition Orbitals and Spin-Forbidden Transitions

“…Recent applications of the NTO method have been primarily in photochemistry and -physics and studies of excited states. A small selection of available studies is presented by refs − . Visualization of NTOs has been particularly useful for systems for which the descriptions of an electronic transition of interest involve a considerable number of pairs of occupied and unoccupied MOs with relatively low weights, which renders the assignment of the excitation difficult.…”