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Steady-state and time-resolved fluorescence was used to investigate the solvation and rotational dynamics of coumarin 153 (C153) and coumarin 343 (C343) in binary solutions of methanol and glyceline, a deep eutectic solvent (DES) composed of a 1:2 molar ratio of choline chloride and glycerol. Time-resolved Stokes shifts were used to quantify the solvation dynamics and were found to be biexponential for both C153 and C343 with nearly identical integral solvation times. The solvation times were also found to be weakly dependent upon solution viscosity, and a power law exponent of p = 0.18 was found for mole fractions of glyceline greater than xDES = 0.2. Solute rotational dynamics were explored using time-resolved fluorescence anisotropy. The reorientation times of C153 and C343 were found to be single exponential at all mixture compositions but did not follow a power-law dependence on solution viscosity. Instead, there was evidence for preferential solvation of the probes by components of glyceline. 

Transient absorption (TA) spectroscopy is a powerful time-resolved spectroscopic method used to track the evolution of excited-state processes through changes in the system's absorption spectrum. Early implementations of TA were confined to specialized laboratories, but the evolution of commercial turn-key systems has made the technique increasingly available to research groups across the world. Modern TA systems are capable of producing large datasets with high energetic and temporal resolution that are rich in photophysical information. However, processing, fitting, and interpreting TA spectra can be challenging due to the large number of excited-state features and instrumental artifacts. Many factors must be carefully considered when collecting, processing, and fitting TA data in order to reduce uncertainty over which model or set of fitting parameters best describes the data. The goal of data preparation and fitting is to reduce as many of these extraneous factors while preserving the data for analysis. In this method, beginners are provided with a protocol for processing and preparing TA data as well as a brief introduction to selected fitting procedures and models, specifically single wavelength fitting and global lifetime analysis. Commentary on a number of commonly encountered data preparation challenges and methods of addressing them is provided, followed by a discussion of the challenges and limitations of these simple fitting methods.