Teisipäeval, 5 juunil 2018 kell 11.15 toimub Physicumis W.Ostwaldi 1 seminariruumis D312
Laserspektroskoopia ja röntgenspektroskoopia seminar No 258
Esineb MARTA BERHOLTS , TÜ FI doktorant , Tartu Ülikool
Fragmentation of ionic and hydrogen-bonded molecules induced by synchrotron radiation (materials of PhD thesis)
In this work, we studied experimentally and computationally the fragmentation processes induced by VUV synchrotron radiation in two diﬀerent types of molecular systems: ionic liquid (IL) and molecular clusters. In particular, the following molecules were studied: 1-ethyl-3-methylimidazolium tetraﬂuoroborate or EMImBF4, acetamide clusters and acetic acid clusters. In the cluster studies, the emphasis was put on the dimers. IL and molecular dimers are diﬀerent by the nature of chemical bonding. Both compounds are overall neutral molecules and can be thought of as the systems composed of two counterparts. In IL, the counterparts (cation and anion) are held together by an ionic bond. Whereas in molecular dimers, the counterparts (two monomer subunits) are held together by hydrogen bonds. The ionic bond in essence is the electrostatic attraction between the oppositely charged ions. The hydrogen bond forms when a hydrogen atom attached to a strongly electronegative atom by a covalent bond, interacts also electrostatically with the lone pair of another electronegative atom of other molecule. Both ILs and clusters are diverse classes of compounds that might take on diﬀerent structures and compositions. Studying interactions of ILs and molecular clusters with ionizing radiation gives valuable insights into the electronic structure and dissociation dynamics of these compounds. A powerful tool to analyze neutral molecules by ionizing them and then separating them in space or time by their molecular weight is mass spectrometry. Ions can easily be guided, focused and separated by electric and/or magnetic ﬁelds, and, ﬁnally, detected. Combination of mass spectrometry with tunable synchrotron radiation allows to explore not only molecular dynamics and dissociation processes but also the energetics of diﬀerent fragmentation pathways. Another widely used method is photoelectron spectroscopy, where not ions but emitted electrons are recorded that provide an image of the energy levels of the molecular orbitals in the photoionized molecule. Photoelectron spectroscopy has a large impact on quantum chemistry in terms of the development of advanced molecular calculations.