Title of Research Group: Atomic, Molecular and Plasma Physics Group

Principal Investigator: Dr Emma Sokell

Institution: University College Dublin

School: Physics

Research:   The Spectroscopy Group conducts research into Atomic, Molecular and Laser Produced Plasma Physics, supporting experimental observations with atomic structure calculations and plasma modeling and simulation. One aspect of these studies is the investigation of double photoionization of atoms and molecules using synchrotron radiation. The high flux, high energy resolution and tunability of synchrotron sources are essential for these experiments. Photoelectron coincidence experiments are challenging, as the count rates are low and two angle and energy resolved electrons must be measured in coincidence. Bu these Triple Differential Cross-Section (TDCS) measurements provide the most stringent test of our understanding of the double photoionization process, in which a single photon liberates two electrons simultaneously.

The UCD group has developed an oven for use on the GASPHASE beamline at the Elettra synchrotron. This oven allows atoms/molecules that are not in the gas phase at room temperature to be studied using coincidence techniques generally applied to gas-phase molecules. We have done collaborative work with researchers from the CNR-ISM in Rome, aimed at extending studies of the double photoionization process, from the archetypal, two-electron helium atom to magnesium and strontium and other alkaline metals with two electrons in their outer shells. The collaboration has used the oven and the multi-coincidence end station available at the GASPHASE beamline to make electron-electron coincidence measurements on magnesium and more recently C60. The electronic structure of this molecule makes it of interest for the development of new materials, relevant to a wide range of applications, including energy storage materials, polymer composites and electronic devices.

The UCD group has its own photoelectron coincidence spectrometer that it is working on coupling to a novel lab-based (soft x-ray/VUV) high brightness source, developed at UCD, to systematically measure photoelectron spectra for fullerenes. The light source was developed by NewLambda Technologies (a spin out company from the UCD group) and in the future it is hoped that synchrotron based work will complement lab-based studies on C60 based systems, of scientific interest from a both an applied and fundamental perspective.

Techniques: Photoelectron Spectroscopy.

Facilities: ELETTRA

Beamlines: GASPHASE (BL 6.2 R) beamline.

Group (as of 2014): 1PI, 1.25 PhD and 1 MSc.

Participating group members at SR/FEL/neutron facilities (period 2008-2014):
1PI, 2 Ph.D and 2 PD.

(Historical information, but not all Irish facility users visit facilities every year)

Impact: Continued access to synchroron facilities in general and Eletrra in particular will enable the Atomic, Molecular and Plasma Physics Group at UCD to continue to perform work of international significance in a field that is of continuing fundamental scientific interest and which has exciting application potential. It will also complement the use of technology developed within the group and expand the networks of members of NewLambda technologies, the Group’s spin-out company.


Quote: “Access to synchrotron light sources has been proven to well equip members of my team for careers in academia or industry.” PI

Publication Highlights:

  1. Signature of Two-Electron Interference in Angular Resolved Double Photoionization of Mg

Phys. Rev. Lett. 110, 083001 – Published 20 February 2013, E. Sokell, P. Bolognesi, A. Kheifets, I. Bray, S. Safgren, and L. Avaldi (DOI: http://dx.doi.org/10.1103/PhysRevLett.110.083001)

  1. Photo-double-ionization of Mg studied by electron-electron-coincidence experiments

Phys. Rev. A 89, 013413 – Published 21 January 2014, E. Sokell, P. Bolognesi, A. Kheifets, I. Bray, S. Safgren, and L. Avaldi (DOI: http://dx.doi.org/10.1103/PhysRevA.89.013413)

  1. Resonant triple-differential cross-section measurements on atomic strontium

Phys. B: At. Mol. Opt. Phys. 41 165204-Published August 2008, P Sheridan, M Grimm and E Sokell (doi:10.1088/0953-4075/41/16/165204)

Website: http://www.ucd.ie/speclab/ AND http://www.ucd.ie/physics/staff/academics/emmasokell/home/