X-ray Absorption and Fragmentation as Initial Steps of Radiation Damage in Free Organic Molecules and Nanoparticles

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Linnanmaa, auditorium L2. Remote connection: https://oulu.zoom.us/j/61348167056

Topic of the dissertation

X-ray Absorption and Fragmentation as Initial Steps of Radiation Damage in Free Organic Molecules and Nanoparticles

Doctoral candidate

Master of Science Abdul Rahman Abid

Faculty and unit

University of Oulu Graduate School, Faculty of Science, Nano and Molecular Systems Research Unit (NANOMO)

Subject of study

Physics

Opponent

Doctor of Philosophy Laurent Nahon, Synchrotron SOLEIL, Saint-Aubin, France

Custos

Professor Marko Huttula, University of Oulu

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X-ray Absorption and Fragmentation as Initial Steps of Radiation Damage in Free Organic Molecules and Nanoparticles

Understanding the molecular radiation damage is crucial in radiobiology, molecular physics, and atmospheric science. In this thesis, the initial steps of radiation damage of anhydrous gas-phase molecules and hydrated nanoparticles were studied using synchrotron radiation based electron-ion coincidence spectroscopy and X-ray absorption spectroscopy under vacuum conditions.

Electron - ion coincidence spectroscopy was used to study the photofragmentation and molecular dynamics of the isolated gas-phase molecules. In addition to the photofragmentation of the gas-phase molecules, the effect of the initial ionization site, initial molecular geometry, and the intramolecular chemical environment has been studied. In avobenzone, core ionization leads to massive fragmentation, with a slight site-selectivity concerning fragment production. In ortho-aminobenzoic acid, core ionization leads to the production of a hydronium ion, indicating that the importance of functional group's position for double intramolecular hydrogen transfer.

X-ray absorption spectroscopy was used to probe hydrated nanoparticles prepared at different relative humidities. In hydrated inorganic and mixed inorganic-organic nanoparticles, water is present in a liquid-like state. With different ranges of relative humidity, the primary hydration layers of the hydrated nanoparticles stays the same. In mixed nanoparticles, there is evidence for interaction between the included organic biomolecule with the inorganic and/or water molecules.
Last updated: 25.3.2021