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Photoelectron spectroscopy of the protoporphyrin IX dianion

Gibbard, Jemma A.; Clarke, Connor J.; Verlet, Jan R.R.

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Dr Jemma Gibbard
Royal Society University Research Fellow

Connor J. Clarke


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.


Gibbard, J. A., Clarke, C. J., & Verlet, J. R. (2021). Photoelectron spectroscopy of the protoporphyrin IX dianion. Physical Chemistry Chemical Physics, 23(34),

Journal Article Type Article
Acceptance Date Aug 7, 2021
Online Publication Date Aug 16, 2021
Publication Date 2021
Deposit Date Nov 16, 2021
Publicly Available Date Nov 16, 2021
Journal Physical Chemistry Chemical Physics
Print ISSN 1463-9076
Electronic ISSN 1463-9084
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 23
Issue 34


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