| Resonance enhanced multi-photon ionization (REMPI) is an important technology of laser spectroscopy and has been applied in many area depending on its high sensitivity, high selectivity and high resolution properties since it is introduced in 1960s. It's an effective technique in studying molecular energy levels, analyzing material compositions, and detecting environmental pollutants.Amine exists generally in organic and biological compounds. Methylamine is the simplest amine, so the study of its energy levels is very important to reveal amines properties. Even though many kinds of methods including fluorescence spectroscopy, infrared spectroscopy and electronic impact spectroscopy has been used , the resonance enhanced multiphoton ionization technique made the study of methylamine fine and deep.The studying of methylamine REMPI mass spectrum revealed that methylamine dissociated according to the ladder mechanism when the mother ion was formed by laser ionization, but the detail fragmented channels was still unconfirmed. From the methylamine REMPI spectrum, we observed transition bands in the range of 41680cm"1 which assigned to the (Nn â†'3s) electronic transition. Comparing with theoretical calculation results, we identified the NH2-wagging vibrational mode which energy is about 634cm"1.The polarization direction of laser has great effect on REMPI mass spectrum. Using polar molecule acetone and non-polar molecule oxygen, we studied their different dependence on laser polarization direction.The thesis includes the following aspects:1. Introduction of the single photon ionization technique and the development of multiphoton ionization technique.2. Experiment equipments.3. Through analyzing the dependence of ion signal intensity on laser... |
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