Dynamics of electron solvation in methanol: Excited state relaxation and generation by charge-transfer-to-solvent

Abstract

The charge-transfer-to-solvent dynamics (CTTS) and excited state relaxation mechanism of the solvated electron in methanol are studied by time-resolved photoelectron spectroscopy on a liquid methanol microjet by means of two-pulse and three-pulse experiments. In the two-pulse experiment, CTTS excitation is followed by a probe photoejection pulse. The resulting time-evolving photoelectron spectrum reveals multiple time scales characteristic of relaxation and geminate recombination of the initially generated electron which are consistent with prior results from transient absorption. In the three-pulse experiment, the relaxation dynamics of the solvated electron following electronic excitation are measured. The internal conversion lifetime of the excited electron is found to be 130 ± 40 fs, in agreement with extrapolated results from clusters and the non-adiabatic relaxation mechanism.

Isotope effect on hydrated electron relaxation dynamics studied with time-resolved liquid jet photoelectron spectroscopy

“…The liquid microjet photoelectron spectrometer used for these experiments has been described previously. 52 Briefly, a solution of potassium iodide (100 mM, Fischer) in water (18 MΩ, Millipore) or deuterium oxide (99.98% Cambridge Isotope Laboratories) is injected at high backing pressure, 80-130 atm, through a 20 µm fused silica capillary into vacuum. The flow rate is held at 0.33 ml/min for both water and heavy water, resulting in a jet velocity of ∼13 m/s.…”

“…43 Additional insights into hydrated electron dynamics are obtained from time-resolved photoelectron spectroscopy experiments on gas phase water cluster anions [38][39][40]44,45 and solvated electrons in liquid microjets. [46][47][48][49][50][51][52] In the cluster experiments, (H 2 O) − n and (D 2 O) − n clusters as large as n = 200 were generated and studied using TRPES. [38][39][40]44,53,54 These experiments showed a clear separation between the s and p states, allowing for conclusive identification of the internal conversion lifetime.…”

Dynamics of dipole- and valence bound anions in iodide-adenine binary complexes: A time-resolved photoelectron imaging and quantum mechanical investigation

“…When possible, a global fitting procedure was applied. In global fitting, the entire spectrum is fit simultaneously in energy and time with shared parameters according to the following equation: 76,77…”

Excess electrons in methanol clusters: Beyond the one-electron picture

“…3,4,5,6,7,8,9,10 Extension of the experimental techniques to the gas phase has made it possible to investigate solvated electrons in methanol clusters in the last decade. 11,12,13 Due to the fewer degrees of freedom of the solvating molecules, cluster experiments provide more tangible information on the underlying microscopic details of the solute-solvent interaction and dynamics. 14 Ultrafast photoelectron imaging technique revealed two distinctly different, sizedependent trends of the vertical detachment energy (VDE) of the excess electron in methanol clusters.…”