Photoexcited processes in ionic liquid vapors

Abstract

Ioonsed vedelikud (IL-id) on üldiselt määratletud kui sulanud orgaanilised soolad, mille sulamistemperatuur on alla 100 °C. IL-id koosnevad orgaanilistest katioonidest, mis on seotud kas orgaaniliste või anorgaaniliste anioonidega. Käesolev väitekiri uurib valitud ioonvedelike elektronstruktuuri aurufaasis, keskendudes sellele, kuidas erinevad aniooni–katiooni kombinatsioonid mõjutavad nende elektronstruktuuri. Ioonvedelikud aurustati kõrgvaakumis kasutades efusioonirakku. Ultraviolett-fotoelektronspektroskoopia (UPS) ja lennuaeg-massispektromeetria (TOF-MS) mõõtmised viidi läbi MAX IV labori uuel FinEstBeAMS kiirekanalil, mille rajamisse ja optimeerimisse panustas ka autor. Ioonvedelike uurimise käigus mõõdeti ja avaldati esmakordselt rohkem kui kümne ioonvedeliku – [EMIM][OTf], [PYR₁₄][OTf], [EMIM][DCA], [PYR₁₄][DCA], [PYR₁₄][TCM], [PYR₁₄][FSI], [PYR14][PF₆], [S₂₂₂][TFSI], [P₄₄₄₁][TFSI] ja [EMMIM][TFSI] UPS-i ning mõnel juhul ka TOF-MS-i spektrid. TOF-MS uurimus [EMMIM][TFSI], [EMIM][OTf] ja [EMIM][DCA] fragmenteerumisest näitas hüdrogeenitud ja dehüdrogeenitud fragmentide esinemist. [EMIM][DCA] elektronstruktuuri uuriti põhjalikult. Näidati, et [EMMIM][TFSI] ja [EMIM][OTf] fragmenteerumismustrid on sarnased.

Ionic Liquids (ILs) are generally defined as molten organic salts with a melting point below 100 °C. ILs are composed of organic cations paired with either organic or inorganic anions. This thesis examines the electronic structure of selected ionic liquids in the vapor phase, with a focus on how different anion–cation combinations affect their electronic structure. The ILs were vaporized in a high-vacuum environment using an effusion cell. Ultraviolet photoelectron spectroscopy (UPS) and time-of-flight mass spectrometry (TOF-MS) measurements were performed at the new FinEstBeAMS beamline at the MAX IV Laboratory, where the author contributed to the construction and optimization. During the studies of ILs, the first UPS and in some cases TOF-MS spectra of the vapors of more than 10 ionic liquids: [EMIM][OTf], [PYR₁₄][OTf], [EMIM][DCA], [PYR₁₄][DCA], [PYR₁₄][TCM], [PYR₁₄][FSI], [PYR14][PF₆], [S₂₂₂][TFSI], [P₄₄₄₁][TFSI] and [EMMIM][TFSI] were obtained and published. The TOF-MS study on the fragmentation of [EMMIM][TFSI], [EMIM][OTf] and [EMIM][DCA] revealed the presence of interesting hydrogenated and dehydrogenated fragments. The electronic structure of [EMIM][DCA] was thoroughly investigated. It was shown that [EMMIM][TFSI] and [EMIM][OTf] have similarities in the fragmentation pattern.