Doctoral defence in Chemistry - Mengxu Jiang

Ph.D. student: Mengxu Jiang
Dissertation title: Dynamics and energetics relevant to multiphoton excitation via Rydberg and Ion-pair molecular and atomic states
Dr. Peter Rakitzis, Professor at the University of Crete
Dr.Egill Antonsson, Research Scientist, Hessian Agency for Nature Conservation, Environment and Geology, Kassel (Germany)
Advisor: Dr. Ágúst Kvaran, Professor at the Faculty of Physical Sciences, University of Iceland
Doctoral committee: 
Dr. Victor Huasheng Wang, Research Scientist and Project Manager at the Science Institute, University of Iceland
Dr. Jingming Long, Application Scientist, Amsterdam Scientific Instruments B.V., Amsterdam, Netherland
Dr. Gísli Hólmar Jóhannesson, Division Director at Keilir, Iceland
Dr. Sveinn Ólafsson, Research Scientist at the Science Institute, University of Iceland
Chair of Ceremony: Dr. Einar Örn Sveinbjörnsson, Professor and Head of the Faculty of Physical Sciences, University of Iceland
The research focused on the multiphoton dynamics and energetics for the HI, CH3I, CH3Br and C2H2 molecules, by using one- and two- color mass-resolved (MR) resonance enhanced multiphoton ionization (REMPI) and/or velocity map imaging (VMI) in association with REMPI.
MR-REMPI experiments for HI revealed new Rydberg and ion-pair states as well as perturbation cases due to interactions between electronic states, which appeared as line-shift (LS), line-intensity (LI) and line-width (LW) alternations in REMPI spectra.
CH3I multiphoton dynamic studies by VMI-REMPI revealed formation of excited Rydberg states of iodine atoms (I**) along with CH3(X) to be the major formation channel in the two-photon excitation region of 55 700 to 70 000 cm-1. This, rather unusual observation, was found to occur via three-photon excitation to superexcited molecular states (CH3I#).
Iodine atomic lines in REMPI spectra for I+ signals in the two-photon excitation region of 76 680 -82 620 cm-1 for CH3I and HI revealed autoionization of superexcited iodine atoms (I#). Several new spectral peaks were assigned and the autoionization mechanisms identified.
Two-color MR-REMPI / pump and probe experiments were designed and developed to perform photofragmentation experiments and spectra analysis of fragment species. The technique was successfully applied for CH3Br. Further work is in preparation.
Multiphoton breakdown of acetylene (C2H2) was studies by VMI-REMPI via molecular Rydberg states. Number of photofragmentation channels, involving formation of ground and excited state fragments for two-, three- and four- photon excitations, prior to photoionization, were identified.
 About the doctoral candidate
Mengxu Jiang was born in Suzhou, China in 1993. He graduated with BS degree in Chemical Engineering in 2015 and a MS degree in Chemical Engineering and Technology  in 2018 from Northeast Electric Power University, Jilin, China.
Later that year he started his doctoral studies in Chemistry at the University of Iceland.
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