Effects of resonant excitation, pulse duration and intensity on photoelectron imaging of a dianion

Abstract

. (2014) 'E ects of resonant excitation, pulse duration and intensity on photoelectron imaging of a dianion.', Physical chemistry chemical physics., 16 (2). pp. 489-496. Further information on publisher's website:http://dx.doi.org/10.1039/c3cp53235fPublisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The photoelectron imaging of the indigo carmine dianion is used to demonstrate the effects of resonance excitation, pulse duration and pulse intensity on the photoelectron spectra and angular distributions of a dianion. Excitation of the S 1 state leads to an aligned distribution of excited state dianions. The photoelectron angular distribution following subsequent photodetachment within a femtosecond laser pulse is primarily determined by the repulsive Coulomb barrier. Extending the timescale for 10 photodetachment to nanoseconds leads to dramatic changes in both the spectra and angular distributions. These observations are explained in terms of statistical detachment of electrons, either from the monoanion, or from the ground state of the dianion following a number of photon cycles trough the S 1 ← S 0 transition. At high intensity, new electron emission channels open up, leading to emission below the repulsive Coulomb barrier. This has been assigned to strong-field induced detachment and the effect of an 15 electric field on the Coulomb barrier is discussed in terms of the photoelectron spectra and angular distributions.

Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

“…Verlet and co-workers have been able to achieve such alignment using pump-probe experiments of two doubly charged dye molecules, pyrromethene 556 (PM 2− ) and doubly deprotonated indigo carmine. 36,[94][95][96] Both dianions consist of a central aromatic system with two terminal sulfonate groups and a π HOMO on the aromatic system, very similar to the diphenyl disulfonate dianion shown in Fig. 3(a).…”

“…106 Verlet and co-workers have recently coupled pump-probe experiments with PE imaging to probe the dynamics of MCAs and the effects of the RCB. [94][95][96]107,108 In an experiment on the deprotonated fluorescein dianion, they pumped the dianion to its S 1 excited state within the RCB and observed strong resonant tunneling. 107 They observed that the electron kinetic energies from the resonant tunneling and the tunneling lifetimes are constant when the pump laser was tuned to different vibronic levels of the S 1 state.…”

“…As shown below, Verlet and co-workers have also observed perpendicular PE angular distributions for several dianions with similar structures and charge carriers. [94][95][96] …”

Excited states of multiply-charged anions probed by photoelectron imaging: riding the repulsive Coulomb barrier

“…In this case, the electron emission is from a central chromophore so that the final state is in fact an anion which has two localised terminal negative charges and a positive hole at the centre. 24 The RCB can be estimated in much the same manner by treating each charge as a point charge and calculating 40 the interaction of an e -with this total potential. 24 This yields an RCB height of 0.84 eV, which corresponds to κ = 1.31 and this is likely correlated with the delocalised hole.…”

“…24 The RCB can be estimated in much the same manner by treating each charge as a point charge and calculating 40 the interaction of an e -with this total potential. 24 This yields an RCB height of 0.84 eV, which corresponds to κ = 1.31 and this is likely correlated with the delocalised hole. A key point to note is that the height of the RCB effectively provides a distance measurement between well-localised charge sites in a molecular 50 MCA.…”