Issue 34, 2021

Photoelectron spectroscopy of the protoporphyrin IX dianion


Two-dimensional photoelectron spectroscopy using nanosecond and femtosecond lasers has been used to study the protopophyrin IX dianion at photon energies between 1.8–4.1 eV. The photoelectron spectra indicated the presence of two direct detachment channels, tunnelling through the repulsive Coulomb barrier (RCB) and thermionic emission from monoanions. A direct detachment feature suggested a near 0 eV electron affinity, which may be attributable to the repulsive through space interaction of the unshielded carboxylate groups. The minimum height of the repulsive Coulomb barrier (RCB) was found to be between 1.4–1.9 eV. Adiabatic tunnelling through the RCB was seen to occur on a timescale faster than rotational dephasing of the molecule. The observation of thermionic emission below the RCB in the nanosecond spectra originated from monoanions, which were produced via photon-cycling of the dianion.

Graphical abstract: Photoelectron spectroscopy of the protoporphyrin IX dianion

Article information

Article type
06 Jul 2021
07 Aug 2021
First published
16 Aug 2021
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2021,23, 18425-18431

Photoelectron spectroscopy of the protoporphyrin IX dianion

J. A. Gibbard, C. J. Clarke and J. R. R. Verlet, Phys. Chem. Chem. Phys., 2021, 23, 18425 DOI: 10.1039/D1CP03075B

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