Photodissociation Dynamics Study Of Butadiene Molecular And Ab Initio Study Of Hydrogen-bond Cluster

This thesis has two parts: one is the photodissociation dynamics of median sizemolecules; the other is the ab inito study of hydrogen-bond cluster.Photofragment translational spectroscopy (PTS) is an ideal tool to investigatephotodissociation dynamics under collision-free conditions through which one canobtain the product translational distribution, angular distribution, and the branchingratios for the different product channels by measuring the angle-resolved time offlight (TOF) spectra of all photofragments. In the first part of this thesis,photodissociation dynamics of 1,2-Butadiene and 1,3-butadiene at 157nm have beeninvestigated using photofragment translational spectroscopy (PTS) technique. Thisexperiment has been carried out using a newly built crossed molecular beamapparatus, the photofragments are ionized with tunable VUV light from U9 (9 cmperiod undulator) white light beamline at the National Synchrotron RadiationResearch Center in the Hsinchu, Taiwan.Signals of the photodissociation products from 1,2-butadiene photolysis atmasses 1,2, 15, 26, 27, 28, 39, 52, 53 have been detected. After careful measurementand detailed analysis of the TOF spectra, six dissociation pathways have beenidentified. The observed channels are C₄H₅ + H, C₄H₄ + H₂, C₃H₃ + CH₃, C₂H₃ + C₂H₃,C₂H₄ + C₂H₂, and C₄H₄ + H + H. C₃H₃ + CH₃ is found to be the dominant channel. Theproduct kinetic energy distributions of all dissociation channels have beendetermined from simulating the experimental time of flight spectra. Relativebranching ratios for all observed dissociation channels were also estimated to be: 0.6 :1 : 82.6 : 8.6 : 1.8 : 5.4, correspondingly.Photodissociation of 1,3-butadiene at 157nm has also been investigated. We haveidentified six dissociation channels including C4H5 + H, C4H4 + H2, C3H3 + CH3,C2H3 + C2H3, C2H4 + C2H2, and C4H4 + H + H. The product kinetic energydistributions for all dissociation channels have been determined. The relativebranching ratios for the above channels have also been estimated: 0.4 : 2 : 41.2 :29.8 : 22 : 4.6, correspondingly In addition, the N-methylformamide(NMF)-water clusters were studied by abinito calculations at MP2/6-31+G** and MP2/6-311++G (d, p) levels. Theequilibrium geometries and the dissociation channels and dissociation energies ofboth neutral and ionic NMF-H2O clusters are presented.