Separating single- from multi-particle dynamics in nonlinear spectroscopy

Excitonic coupling of RNA-templated merocyanine dimer studied by higher-order transient absorption spectroscopy

“…S4 for the pump-power dependence). 17 The probe-chirp-corrected transient map corresponding to the pure third-order response (Fig. 3b) shows a strong negative band at 515 nm and a weaker negative feature at 570 nm.…”

“…Here, we use our recently developed technique 17 of separating single-and multi-exciton dynamics in transient absorption spectroscopy by means of systematic intensity variation of the pump pulse for a better insight into excitonic coupling interactions within a merocyanine dimer in an RNA duplex and to unravel information about how the exciton dynamics evolve in this new merocyanine dimer. The rBAM2 free nucleoside (3, rBAM2 free ), in which the polymethine chain is lengthened by one vinylene unit (m(C 2 H 2 ) = 2) compared to the previously reported rBAM (m = 1) 16 leading to a red-shift of the absorption maximum by about 100 nm, 20 was prepared by condensation of the barbituric acid b-D-ribofuranoside 1 16 and the chromophore precursor 2 18,19 (Fig.…”

“…18,19 To further analyze the dynamics associated with the excitonic manifold of the chromophores in rBAM2-D2, we used our technique of separating single-and multi-exciton dynamics in transient absorption (TA) spectroscopy by means of systematic intensity variation of the pump pulse. 17 This technique makes use of the perturbative formulation of nonlinear response and the measurement of pump-probe spectra at specific pump intensities to disentangle signal pathways corresponding to different orders of nonlinearity. Maly ´et al 17 have developed a method to separately filter out the pure, i.e., contamination-free, third-order signal along with other pure higher-order signals.…”

“…17 This technique makes use of the perturbative formulation of nonlinear response and the measurement of pump-probe spectra at specific pump intensities to disentangle signal pathways corresponding to different orders of nonlinearity. Maly ´et al 17 have developed a method to separately filter out the pure, i.e., contamination-free, third-order signal along with other pure higher-order signals. This enables one to study unexplored photophysical pathways associated with higher-order signals within the framework of ultrafast TA spectroscopy.…”

“…Similarly fast dynamics have also been reported in covalently linked squaraine dimers and trimers. 17,24,25 After EEA, only one exciton remains, which is reflected by the signal decay with the single-exciton lifetime (ESI, † Fig. S8).…”