Issue 23, 2022

Femtosecond dynamics of stepwise two-photon ionization in solutions as revealed by pump–repump–probe detection with a burst mode of photoexcitation

Abstract

Pump–repump–probe spectroscopy with a burst mode of photoexcitation was applied to the direct observation of the photoionization dynamics of perylene in the solution phase. Irradiation of a pump pulse train generated with birefringent crystals effectively accumulated an intermediate S1 state and a repump pulse triggered photoionization in the higher excited state, ensuring sufficiently large signal intensity to probe. Two-photon excitation to the energy level, which is 0.7 eV lower than the ionization potential in the gas phase, results in instantaneous formation of the radical cation of perylene in acetonitrile, unlike aromatic amines in previous reports. In addition, subsequent recombination dynamics between the radical cation and ejected electron was monitored in polar and nonpolar solvents. The ultrafast recombination in nonpolar solvents suggests that the distribution of the distance in the cation-ejected electron pair largely evolves even in acetonitrile in the femtosecond timescale, in which the solvation is not completed and the dielectric constant is still low. The recombination process in acetonitrile was well reproduced with simulations based on the Smoluchowski equation taking account of the transient change in the dielectric constant by solvation.

Graphical abstract: Femtosecond dynamics of stepwise two-photon ionization in solutions as revealed by pump–repump–probe detection with a burst mode of photoexcitation

Supplementary files

Article information

Article type
Paper
Submitted
23 avq 2021
Accepted
24 apr 2022
First published
25 apr 2022

Phys. Chem. Chem. Phys., 2022,24, 14187-14197

Femtosecond dynamics of stepwise two-photon ionization in solutions as revealed by pump–repump–probe detection with a burst mode of photoexcitation

H. Sotome, M. Koga, T. Sawada and H. Miyasaka, Phys. Chem. Chem. Phys., 2022, 24, 14187 DOI: 10.1039/D1CP03866D

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