An ultrafast algorithm for ultrafast time-resolved coherent Raman spectroscopy

Time-resolved coherent Raman spectroscopy (CRS) is a powerful non-linear optical technique for quantitative, in-situ analysis of chemically reacting flows, offering unparalleled accuracy and exceptional spatiotemporal resolution. Its application to large polyatomic molecules, crucial for understanding reaction dynamics, has thus far been limited by the complexity of their rotational-vibrational Raman spectra. Progress in developing comprehensive spectral codes for these molecules, a longstanding goal, has been hindered by prohibitively long computation times required for their spectral synthesis. Here, we present an algorithm that achieves a million-fold improvement in computation time compared to existing methods. The algorithm demonstrates remarkable accuracy, with an approximation error below 0.1% across all tested probe delays, at both room temperature (296 K) and elevated temperatures (1500 K). This result could greatly expand the application of time-resolved CRS, particularly in plasma research, as well as in broader atmospheric and astrophysical sciences. Time-resolved coherent Raman spectroscopy is a powerful diagnostic technique for the quantitative, in situ analysis of chemically reacting flows, but its application to large polyatomic molecules has been hindered by the complexity of their rotational-vibrational Raman spectra. Here, the authors develop a spectral synthesis algorithm that achieves a million-fold improvement in computation time compared to prior efforts while maintaining high numerical accuracy.