Time-of-Flight Ion and Electron Spectroscopy: Applications and Challenges at Storage Ring Light Sources
Author
Summary, in English
This dissertation contains seven studies exploring novel instrumentation for ion and electron spectroscopy, including their applicability at storage ring light sources. The studies focus on instrumentation to study decay, dynamics and dissociation of photoexcited molecules, and the possibility to host such instruments at MAX~IV.
Commissioning of an instrument for negative-ion/positive-ion coincidence spectroscopy is reported and its design considerations are discussed.
The instrument allows detection of coincidences between mass-resolved negative and (multiple) positive ions, which is demonstrated in a study on the water molecule. Coincidence yields were measured following soft x-ray excitation below and above the O 1s ionization threshold of H2O. Analysis of such yields enhances the present understanding of the dissociation process of the water molecule and allows, for example, designation of previously unchartered doubly excited states and their decay channels. A second study of energy-resolved Auger electrons and mass-resolved positive ions in coincidence provides new data on the non-radiative decay of core-excited and--ionized water molecules.
A study using a novel instrument for mass-resolved analysis of highly excited neutral molecular fragments is reported. Such "high Rydberg" states are associated with electron recapture above the ionization threshold. They can also be reached following resonant Auger decay from core--excited states below threshold. The instrument is utilized in a study on the methane molecule.
The advent of high-resolution, high-transmission time-of-flight electron spectrometers sets new opportunities for spectroscopy at MAX IV, provided that the timing constraints of such instruments can be met. This dissertation proposes, based on initial experimental studies and theoretical considerations, that an ultra-high resolution electron coincidence experimental station could be constructed at MAX IV. This proposed station combines strengths of hemispherical analysers and time-of-flight instruments. The unique time-structure of the MAX IV storage rings with 10~ns light pulse separation allows for better performance than at other laboratories. Recent developments in chopper technology and so called pseudo single bunch techniques could open up possibilities to run timing-based instrumentation and experiments with high intensity demands in parallel. This dissertation reviews possible adaptations to MAX IV accelerators and beamlines to allow for future inclusion of timing-based spectroscopic instruments.
Commissioning of an instrument for negative-ion/positive-ion coincidence spectroscopy is reported and its design considerations are discussed.
The instrument allows detection of coincidences between mass-resolved negative and (multiple) positive ions, which is demonstrated in a study on the water molecule. Coincidence yields were measured following soft x-ray excitation below and above the O 1s ionization threshold of H2O. Analysis of such yields enhances the present understanding of the dissociation process of the water molecule and allows, for example, designation of previously unchartered doubly excited states and their decay channels. A second study of energy-resolved Auger electrons and mass-resolved positive ions in coincidence provides new data on the non-radiative decay of core-excited and--ionized water molecules.
A study using a novel instrument for mass-resolved analysis of highly excited neutral molecular fragments is reported. Such "high Rydberg" states are associated with electron recapture above the ionization threshold. They can also be reached following resonant Auger decay from core--excited states below threshold. The instrument is utilized in a study on the methane molecule.
The advent of high-resolution, high-transmission time-of-flight electron spectrometers sets new opportunities for spectroscopy at MAX IV, provided that the timing constraints of such instruments can be met. This dissertation proposes, based on initial experimental studies and theoretical considerations, that an ultra-high resolution electron coincidence experimental station could be constructed at MAX IV. This proposed station combines strengths of hemispherical analysers and time-of-flight instruments. The unique time-structure of the MAX IV storage rings with 10~ns light pulse separation allows for better performance than at other laboratories. Recent developments in chopper technology and so called pseudo single bunch techniques could open up possibilities to run timing-based instrumentation and experiments with high intensity demands in parallel. This dissertation reviews possible adaptations to MAX IV accelerators and beamlines to allow for future inclusion of timing-based spectroscopic instruments.
Department/s
Publishing year
2016
Language
English
Full text
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Document type
Dissertation
Publisher
MAX IV Laboratory, Lund University
Topic
- Physical Sciences
Status
Published
Research group
- Department of Synchrotron Radiation Instrumentation
Supervisor
ISBN/ISSN/Other
- ISBN: 978-91-7623-649-9
- ISBN: 978-91-7623-648-2
Defence date
15 April 2016
Defence time
13:15
Defence place
MAX III Seminar Room, MAX IV Laboratory
Opponent
- Lorenzo Avaldi (Prof.)