Theoretical Studies Of Stereodynamics And Nonadiabatic Dynamics For Several Elementary Reactions

Molecular reaction dynamics is a science which studies the chemical elementary reactions in atom and molecular level to learn the microscopic mechanism of the chemical reaction process. The stereodynamics not only focus on the scalar properties of the reactions, but also pays attestation to the vector and its distribution. In this paper we use the classical method, quantum mechanics method and quantum-classical methods to perform different kinds of reactions including:S(3P)+HD, H+CH4,O+CH4, D++H2 and Na+H2. The time dependent wave packet (TDWP) method is employed in the reaction S(3P)+HD, which does not have a long-life complex. For the reaction with more than three atoms, the three-atom approximation is used with the qusiclassical trajectory method (QCT). To perform the non-adiabatic system D++H2 and Na+H2, the coherent switching with decay of mixing (CSDM) method is adopted. The specific research of this paper includes several aspects as follows:(1) For reaction S(3P)+HD. the calculations have been carried out at the lowest 13A" state with both rotational and vibrational excitations of reactant HD. The calculated integral cross sections (ICS) from QCT agree fairly well with the TDWP calculations. The reaction probability results from TDWP show that the reaction displays a strong tendency to the SD channel. When the reactant HD is vibrationally excited, both of the two channels are promoted apparently. The vibration of HD bond tends to reduce the difference of reactivity between the two channels. The detailed state-to-state differential cross sections (DCSs) are calculated. These distributions show some significant characters of the barrier type reactions. At the same time, the scattering width of product SD has certain relationship with its rotation excitation. For the vector properties, P(?r), P(?r) and P(?r,?r) distributions are calculated by QCT, and the increased collision energy weakens the rotational polarization of the SD molecule.(2) In the investigation of H+CD4 system, the calculated excitation function of the title reaction can give a good agreement to most experimental and theoretical data at collision energy Ec=1.5?2.5 eV. Further investigation of the product HD in reaction H+CD4(v=0, j=0) ? HD +CD3 and D+CH4(v=0, j=0) ? HD+CH3 shows the dependence of the product rotational polarization on collision energy and mass factor, but P(?r) is not sensitive to both the collision energies and the mass factor.(3) For O+CD4, our calculations have been taken at the collision energy Ec=1.5?2.5 eV, and the excitation function resulted from the QCT method agrees rather well with the experimental data. The product rotational polarization is calculated, the products shows a strong rotational polarization in the center of mass coordinate system. The orientation of the product rotational angular momentums is sensitive to the increasing collision energy. The alignment of the product rotational angular momentums shows some properties of the "heavy+heavy-light ? heavy-heavy+light" mass combination reactions. In the isotopic substituted reaction study, when H atoms in methane are replaced by D atoms, the rotational polarization is reduced obviously. Then the polarization-dependent differential cross section (PDDCS) is also studied by this QCT calculation to provide detailed information about the product rotational alignment and orientation.(4) The reaction D++H2(v, j= 0) is calculated for both reactive non-charge transfer and charge transfer channels. For the non-charge transfer channel, it is found that the influence of the non-BO effect on the DCS is quite small, but it has a large impact on the rotational polarization of HD product which is reflected by the joint distribution P?r,?r). And it is also found that the polarization of the charge transfer products show quite different form. The rotational polarizations are also investigated at various collision energy and initial vibrational states for both reactive channel.(5) For reaction Na(3s)+H2 ? NaH(X1?+)+H, the integral cross sections calculated by the CSDM method are compared with those of an adiabatic QCT calculation, which uses the potential energy diagonalized by the same matrix. The product rotational polarization in non-adiabatic dynamics is presented and compared with the adiabatic results by means of the joint distributions of rotational angular momentum vectors in the scattering coordinate. The influence of the conical intersection is discussed for both the scalars and the vectors of the title reaction.