Fluorescence‐Detected Pump–Probe Spectroscopy

Abstract

We introduce an ew approach to transient spectroscopy, fluorescence-detected pump-probe (F-PP) spectroscopy, that overcomes several limitations of traditional PP.F -PP suppresses excited-state absorption, provides background-free detection, removes artifacts resulting from pump-pulse scattering, from non-resonant solvent response,o rf rom coherent pulse overlap,a nd allows unique extraction of excited-state dynamics under certain conditions.D espite incoherent detection, time resolution of F-PP is given by the duration of the laser pulses,i ndependent of the fluorescence lifetime.W e describe the working principle of F-PP and provide its theoretical description. Then we illustrate specific features of F-PP by direct comparison with PP,t heoretically and experimentally.F or this purpose,w ei nvestigate,w ith both techniques,amolecular squaraine heterodimer,c ore-shell CdSe/ ZnS quantum dots,a nd fluorescent protein mCherry.F -PP is broadly applicable to chemical systems in various environments and in different spectral regimes.

High-resolution two-dimensional electronic spectroscopy reveals the homogeneous line profile of chromophores solvated in nanoclusters

“…The weaker diagonal peaks are assigned to the heteromolecular complexes discussed above whose spectral positions coincide exactly with the weak features observed in the 2D spectra. Possible contributions from sample scattering can be excluded in action-detected 2DES 52 . The absence of cross-peaks confirms that these spectral features correspond to individual molecular species which do not couple among each other (cf.…”

Entangled biphoton enhanced double quantum coherence signal as a probe for cavity polariton correlations in presence of phonon induced dephasing

“…In the latter, the cooperative features appearing in the above-mentioned sector carry less specific information regarding the physical origin of the polaritonic correlation due to non-discrimination between pure two-one polariton coherence and twopolariton-one polariton coherence. The study can be extended to accommodate the explicit two-polariton transport phenomenology by studying the fluorescence-detected phase cycling protocols [74,75]. The latter is a four-wave mixing analog but aimed at investigating the longer-time state correlation properties in the presence of phonon-induced dynamical population redistribution.…”

Time-Domain Vibrational Action Spectroscopy of Cryogenically Cooled, Messenger-Tagged Ions Using Ultrafast IR Pulses

“…Alternatively, action-based nonlinear experiments have been described using density matrix nonlinear response formalism, even in dilute gas-phase systems, where the pump and probe pulses each formally provide two simultaneous interactions with the system. 10,13,57,58 The fourth and final interaction places the system into an excited population state, which is read out by the action response. Unlike condensed-phase nonlinear experiments that have three formal field interactions, the action-based four-field scheme results in an additional ESA contribution at ω 21 corresponding to bleaching of the v = 1 level.…”

“…Unlike condensed-phase nonlinear experiments that have three formal field interactions, the action-based four-field scheme results in an additional ESA contribution at ω 21 corresponding to bleaching of the v = 1 level. 57,59 For a harmonic oscillator, these two ESA pathways will cancel leaving only GSB and SE pathways to contribute to the nonlinear signal. This perspective could also be used to explain the presence of a negative nonlinear signal even at the earliest waiting times.…”

“…Critically, we have also shown that nonlinear pump−probe signals are measurable under the current experimental conditions. The next crucial step is to introduce a probe pulse pair 57 in the pump−probe scheme used to collect the nonlinear data presented in Figure 4a to frequency-resolve the bleach and (possibly) ESA transitions and to monitor their time evolution with a pump−probe delay time. The collection of a 2D spectrum will require an additional pump pulse pair.…”