| In this thesis,with a tunable vacuum ultralviolet(VUV)light generated by four-wave mixing,the photodissociation dynamics of the O(3PJ=2,1,0)chaunels from OCS at the photolysis wavelength of around 135 nm has been studied.Meanwhile,the author has also studied the detailed reaction dynamics of H+HD→H2+D reaction at 0.60 and 1.26 eV,whose product is detected by a near-threshold scheme with the VUV light and the other VU light.Carbonyl sulfide(OCS),as the most abundant sulfur compound in the global atmosphere,also plays important roles in the interstellar chemistry.So studies of the OCS’s photodissociation process could help us deepen our understanding of the property for the excited-state OCS and the important chemical process happened in the atmosphere and space.Previous studies always focus on the S atom channel which is the main channel of the photolysis of OCS,and there are few studies that is about the rare O atom channel.The present study was designed to reveal the photodissociation dynamics of OCS+hy→CS(X1∑+)+O(3PJ)reaction,and ion images of atomic oxygen products were collected at five photolysis wavelengths in the vacuum ultraviolent region,corresponding to the symmetric stretching mode excitation of the Rydberg state F.Dynamics Information like the product total kinetic energy release spectrum,angular distributions,and the branching ratios of co-products CS vibrational states,were acquired from the experimental images.It can be found that the anisotropic parameters change with the J value of O(3PJ),the vibrational state of CS(X1∑+)and the photolysis wavelength,and this feature could be qualitative explained by the different coupling of the vibrational state of a series of energetic similar high-lying Rydberg states with shallow well structure.Especially,it can be found that different anisotropic of product is from different J value of O(3PJ)channels at same photolysis wavelengths,which indicate that the spin-orbit coupling has a strong influence on photolysis pathway.Despite the limitation by the lack of more accurate PES information in the VUV region,this study offers further insights into the topological structure near the F Rydberg state and adds to the understanding of VUV photodissociation dynamics.As the simplest bi-molecular elementary reaction system,the H+H2→H2+H reaction system,the dynamics calculation of this reaction could reach the highest precision in theory,and this is a challenge for experimental results to reach such high precision.Especially,the theoretical workers have predicted fast forward scattering angular oscillations could be found due to the interference between the far-side and near-side products at collision energies of specific range.To figure this structure out,experiment with high angular resolution is strongly desired.By using the 1+1’ near threshold ionization velocity map ion imaging technique,state-to-state reactive differential cross sections covered full angular range have been measured for the H+HD→H2+D reaction.High-resolution images of the D products,with the rotational states of the H2 co-products clearly resolved,were acquired at the collision energies of 0.60 eV and 1.26 eV,respectively.It is found that the angular distribution is predominantly backward scattering at the collision energy of 0.60 eV.While at 1.26 eV,where the collision energy is higher,the angular distribution becomes forward-backward scattering.Notably,at both collision energies,the main peaks of backward scattered products gradually shift from backward towards sideways direction as the rotational quantum number of H2 increases,this feature could be partly explained by the line-of-centers nearly elastic specular scattering model.As for the more other peaks at the backward and sideways direction at 1.26 eV,they can only be well reproduced in the results of quantum mechanical calculations which is result from the contribution of the helicity states.Moreover,in the forward direction,fast angular oscillations,which is induced by specific partial waves have also been observed at 1.26 eV at several low rotational states.These features show a strong correlation between the product states and angular distributions,and also indicate the unique role of partial waves in quantum reactive scattering.In addition,a new spherical chamber platform has been set up.This platform has included the molecular beam method,the state-selected resonance enhanced multiphoton ionization technique and the velocity map ion imaging technique.A calibration experiment of oxygen photolysis at 225 nm has been employed to calibrate the imaging performance,and an OCS photolysis experiment at 157 nm has also been applied to verify the availability of the 157 nm excimer.These testing experiments provide the basis for subsequent experiments. |
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