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Influence of the repulsive Coulomb barrier on photoelectron spectra and angular distributions in a resonantly excited dianion.

Horke, D. A. and Chatterley, A. S. and Verlet, J. R. R. (2013) 'Influence of the repulsive Coulomb barrier on photoelectron spectra and angular distributions in a resonantly excited dianion.', Journal of chemical physics., 139 (8). 084302.

Abstract

A photoelectron imaging study of the gas-phase dianion of pyrromethene-556 is presented. The photoelectron spectra and angular distributions following resonant excitation of the S1 excited state with nanosecond and femtosecond laser pulses are compared, and the influence of the repulsive Coulomb barrier (RCB) in both cases evaluated. Photoelectron angular distributions show the effect of molecular alignment due to an allowed electronic excitation and can be understood qualitatively based on the calculated RCB surface using the Local Static Approximation. Comparison between femtosecond and nanosecond excitation reveals marked differences in the photoelectron spectra. While femtosecond experiments confirm that tunneling through the RCB is adiabatic, nanosecond experiments show a broad photoelectron feature peaking near the RCB maximum. This is explained in terms of the lifetime of internal conversion, which has been determined by time-resolved photoelectron spectroscopy to be ∼120 ps: as this is faster than the nanosecond laser pulses, multiple photons can be absorbed through the S1 ← S0 transition which leads to large amounts of internal energy and enables electron detachment directly above the RCB. Fragmentation and detachment from the monoanion are also inferred by the presence of photoelectrons emitted at very low kinetic energy. Our results highlight the difficulty in interpreting photoelectron spectra of polyanions in which a resonant state is excited.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1063/1.4818597
Publisher statement:© 2013 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Horke, D. A., Chatterley, A. S. and Verlet, J. R. R. (2013) 'Influence of the repulsive Coulomb barrier on photoelectron spectra and angular distributions in a resonantly excited dianion.', Journal of chemical physics., 139(8): 084302 and may be found at http://dx.doi.org/10.1063/1.4818597
Date accepted:02 August 2013
Date deposited:28 January 2016
Date of first online publication:August 2013
Date first made open access:No date available

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