An Experimental Investigation On The Multiphoton Dissociation Dynamics Of Carbon And Sulfur Contained Molecule

Atom, molecule or radical can be excited to a specific intermediate state by absorbing m laser photons, then the parent ion can be produced by absorption of another n laser photons. The ion yield can be increased drastically due to resonant absorption, comparing with the ion yield in non-resonant absorption. This multiphoton process is usully called Resonance Enhanced Multiphoton Ionization (REMPI). REMPI technique plays an important role in detecting the high electronic excited states of atoms, molecules and radicals. Especially, when the high power laser is used as excited resource, we can detect high electronic excited states or Rydberg states of molecules and radicals. Besides, we can select the specific quanta states of molecules and radicals due to the coherence of the laser. Because of this, REMPI technique can be used to study molecular spectrum, analytical chemistry, state-resolved detection, photoionization and photodissociation dynamic, laser isotope separation and combustion diagnose. So the investigations of REMPI in different systems have comprehensive value in basic field or applied field.In recently years, the photodissociation of sulfur and carbon contained polyatomic molecule has been attracted much attention because these species play a key role in atmospheric physics, environment pollution and ecological preservation. In this paper, using REMPI-TOF technique, multiphoton dissociation/ionization of sulfur and carbon contained polyatomic molecule has been carried out. The mechanism ofmultiphoton dissociation/ionization was discussed, and some valuable results are obtained. The paper has six chapters. The main contents are listed as following.In chapter one, the background of the REMPI technique and its development, and applied fields are presented. In chapter two, the basic principles of REMPI technique are introduced including the resonance enhanced effect, the selection rule, the mechanism of photoionization and photodissociation, REMPI rate equation and the property of Rydberg state. In chapter three, the REMPI-TOF-MS equipment and the experimental method is introduced. In chapter four, the REMPI-TOF-MS of Carbon disulfide is investigated in the range of 283-289nm. The main results are: (1) The TOF-MS and REMPI spectrum of Carbon disulfide are detected. (2) The TOF-MS of Carbon disulfide is identified; the REMPI spectra of C, S, CS and CS2 are analyzed. (3) The possible mechanism of dissociation/ionization is analyzed. It can be concleded that the main dissociation channel is resonant photoionization of parent molecule followed by photodissociation of parent ion and the further photodissociation or photoionization of the fragments. In chapter five, the REMPI-TOF-MS of methanol are investigated in the range of 279.5-286.5nm. The main results are: (1) The TOF-MS and REMPI spectrum of methanol are measured. (2) The TOF-MS of methanol is identified; the REMPI spectrum of C, CH3 and CH2O are analyzed. (3) The possible mechanism of dissociation/ionization is analyzed, (4) It is shown that the main dissociation channel is non-resonantphotodissociation of parent molecule followed by the further photodissociation or photoionization of the fragments. In chapter six, the REMPI-TOF-MS of acetaldehyde are investigated in the range of 279.5-286.5nm. The main results are: (1) The TOF-MS and REMPI spectrum of acetaldehyde are measured. (2) The TOF-MS of acetaldehyde is identified; the REMPI spectra of C, CH, and CH3 are analyzed. (3) The possible mechanism of dissociation/ionization is analyzed, (4) It is also proposed that the main dissociation channel is non-resonant photodissociation of parent molecule followed by the further photodissociation or photoionization of the fragments.