Quantum Time Dependent Wave Packet Study On The Reagent Vibrational Excitation Effects Of The A+BC Reactions

The reagent vibrational excitation effect in the atom-diatom reaction has received considerable attention in molecular reaction dynamics. In the present thesis, using the time dependent wave packet (TDWP) method, we investaged the effects of reagent vibrational excitation of the H+Li2, S(3P)+D2and Ar+H2reaction and discussed the reaction mechanism.As one of the simple mixed clusters, HLi2trimer has been received a lot of interests both experimentally and theoretically. In order to investage the mechanism of H+Li2reaction, firstly, we constructed a globally accurate double many-body expansion (DMBE) potential energy surface (PES) for HLi2(X2A’). Secondly, using the TDWP method, we obtainted the reaction probabilities and integral cross sections of the H+Li2(X1Σg+â†'Li+LiH(X1Σ+) reaction. Due to the barrierless and exothermic reaction, the energy dependence of integral cross section (ICS) shows a downward trend in the low energy region. The behaviour of the v-dependent ICSs with the increase of collision energy indicates that at low energies, the vibrational excitation of reactant Li2inhibits the reactivity, while it enhances the ICS at high energies. The effect of vibrational inhibition is attributed to the fact that relative to the spacings of vibrational levels for reactant Li, the ones for the product LiH are much larger. So, the collision (translation) energy is much easier to transfer to the vibrational energy of reactant Li2than to enhance the reactivity. Finally, the comparison of CC and CS reaction probabilities and ICSs reveals that the CC results are slightly lager than the CS ones.We presented the TDWP calculations for the S(3P)+D2reaction on the3A’ and3A" PESs. The v-dependent behavior of the ICSs on the two surfaces shows that the vibrational energy drives the reactivity more effective than the translational energy for this reaction. The comparison of the influences of vibrational excitation for different surfaces reveals that the vibrational energies of3A’ PES are more effective than that of3A" in enhancing ICSs. This difference is caused by the different characters of effective potentials on the two PESs.The energy barriers on3A’ PES decrease more quickly than those on3A" PES with the increase of reagent vibrational quantum number. Besides, the effects of vibration excitation of the S(3P)+HD on3A" PES is different between the two product channel of D+SH and H+SD.Based on the I2A’ PES of Liu, we investaged the effects of H2+vibrational excitation on the Ar+H2+â†'ArH++H reaction using the TDWP method. The results indicated that, due to the deep well of this PES, there are resonance structures in the reaction probabilities and ICSs cuvers. The present calculated ICSs are in good agreement with other calculated results and the experimental data. The behaviour of the v-dependent ICSs indicates the vibrational excitation of reagent H2+can not enhance the ICS, which can be attributed to the competitaion between chemical reaction and charge transfer in this reaction. In addition, the rotational excitation of reagent H2+also can not enhance ICS.The thesis is outlined as follows. The basic content of the molecular reaction dynamics and the development of TDWP method are introduced in chapter one. Chapter two gives a brief description of the TDWP method to calculate the reaction probabilities and ICSs. The results and discussion of the vibtational excitation effect on the H+Li2, S(3P)+D2, and Ar+H2+reactions are presented in chapter three, four and five, respectively. The conclusions are summarized in Chapter six.