| Summary: | 博士 === 國立臺灣大學 === 化學研究所 === 105 === The thesis is mainly divided into two parts: roaming pathway following photodissociation of methyl formate and stereodynamics in photodissociation of asymmetric top chiral molecules as oriented. They share the same molecular beam apparatus including a time-of-flight spectrometer coupled with ion imaging. For stereodynamic research, an additional hexapole state selector is installed for molecular orientation. In the first part, the ion imaging of CO (v = 1) was acquired with a (2+1) resonance enhanced multiphoton ionization (REMPI) spectroscopy following photolysis of methyl formate at 248 nm. The obtained low-rotational (J) and high-J components of bimodal rotational distributions are ascribed to roaming and conventional transition state pathways, respectively. The results are consistent with the prediction by quasiclassical trajectory calculations. Further comparison with the results of time-resolved FTIR emission spectroscopy is discussed. In the second part, an additional hexapole state selector is installed to orient an asymmetric top chiral molecule, 2-bromobutane. The obtained photofragment ion images of Br (or Br*) presented an up-down asymmetry, caused by the spatial orientation of 2-bromobutane. As a result, the stereodynamic behavior is looked into to find out asymmetry factor, anisotropy parameter, the angle between transition dipole moment and recoiling velocity and the angle between permanent dipole moment and the recoiling velocity. The photofragment distribution gives the insight into the complex photodissociation dynamics of asymmetric top molecules. The possibility to differentiate enantiomers using a linearly polarized laser is also discussed.
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