Ultrafast Four-Dimensional Coherent Spectroscopy by Projection Reconstruction

Abstract

Multidimensional coherent spectroscopy provides insights into the vibronic structure and dynamics of complex systems. In general, the higher the dimensionality, the better the spectral discrimination and the more information that may be extracted about the system. A major impediment to widespread implementation of these methods, however, is that the acquisition time generally increases exponentially with dimensionality, prohibiting practical implementation. We demonstrate the use of nonuniform sampling based on the projection-slice theorem and inverse Radon transform within the context of a fifth-order, 4D technique (GAMERS) designed to correlate the vibrational contributions to different electronic states. Projection-reconstruction (PRO GAMERS) greatly reduces the data sampling requirements without sacrificing frequency resolution. The sensitivity of this technique is demonstrated to surpass conventional uniform sampling by orders of magnitude. The incorporation of projection-reconstruction into multidimensional coherent spectroscopy opens up the possibility to study the structure of complex chemical, biological, and physical systems with unprecedented detail.

Compressed Sensing for Reconstructing Coherent Multidimensional Spectra

“…Similar results were shown by Sanders et al, who used a matching pursuit algorithm to reconstruct the data from atomic Rb vapor . Hutson et al reconstructed the spectra using nonuniformly sampled data using the projection-slice theorem on the multidimensional coherent spectrum . The results of the spectral band (damping) and the spectral width (frequency) were not analyzed; only the spectra were sparsely reconstructed by the noted methods.…”

“…36 Hutson et al reconstructed the spectra using non-uniformly sampled data, using the projection-slice theorem on the multidimensional coherent spectrum. 37 The results of spectral band (damping) and the spectral width (frequency) were not analysed, only the spectra were sparsely reconstructed by the noted methods. In this work, we compare the reconstruction of sparsely sampled LH2 spectra by LASSO and the recently developed SEMA method 24 .…”

Coherent phenomena in photosynthetic light harvesting: part two—observations in biological systems

“…The development of new techniques is needed to further dissect energy transfer pathways. Spectroscopic techniques that show promise in extracting the nature of coherences and the mixing of vibrational and excitonic coherences are higherdimensional (3D and above) pump-probe techniques (Fidler et al 2010;Zhang et al 2013;Oliver et al 2014;Loukianov et al 2017;Goodknight and Aspuru-Guzik 2017;Harel 2018;Hutson et al 2018). In these techniques, different parts of the spectrum (optical and infrared) are excited to generate a fifthorder correlation map of vibrational and excitonic coherences and can also be coupled to different optical phenomena (such as the Stark effect and circular dichroism).…”

Four-Dimensional Coherent Spectroscopy of Complex Molecular Systems in Solution

“…A more efficient algorithm that takes advantage of the sparsity of the signal in the (ω T 0 , ω T ) plane involves sampling along radial lines at a range of angles through the origin of the (T 0 , T) plane. 31 Besides greatly reducing the number of points to sample, this method includes more points near T = T 0 = 0, where the signal is strongest. With radial sampling, the (ω T 0 , ω T ) dependence of the 6WM signal can be characterized with only n scaling in sample points.…”

“…Significant advances have been made in reducing the acquisition time required to measure a 4D GAMER spectrum using spatial multiplexing methods. We have demonstrated 27 the advantage of spatially encoding pulse time delays in the sample as in GRadient-Assisted Photon-Echo Spectroscopy (GRAPES), 30 which is necessary to make this experiment feasible because it reduces the time needed to acquire a spectrum with n 4 points by a factor of n. In addition, we established 31 that radially sampling the (T 0 , T) plane further reduces the acquisition time by approximately an order of magnitude, with no appreciable loss in resolution. In this method, slices acquired at various angles through the origin of the (T 0 , T) plane are used to reconstruct the 4D GAMER spectrum using the inverse Radon transform (e.g., backprojection algorithm).…”