Theoretical Study Of The Stereodynamics For The O+H₂⁺ Reaction

The ion-molecule and atom-molecular ion reactions have been extensively studied from both experimental and theoretical sides due to its importance in the upper atmospheric,electric discharges and combustion chemistry as well as to interest in its fundamental reaction dynamics.The reactions O⁺ + H₂ and O + H₂⁺ are important in dense interstellar clouds,where subsequent reactions of OH+ with H₂ lead to the formation of H₂O⁺ and H₃O⁺ molecular ions,and has a large interest in the Earth’s ionosphere.Unfortunately,being a typical insertion reaction,there are little studies reported on the dynamics of the O + H₂⁺ interesting system.In 2014,Paniagua et al.constructed the ground（12A"）and the first excited（12A’）PESs of O+H₂⁺ reaction system using the multireference configuration interaction（MRCI）method and the analytic fitting based on a many-body expansion.We found that there is a deep well of the PES with the contour map.We employ the QCT method to investigate the influences of collision energy,ro-vibrational excitation and isotopic on the stereo-dynamics properties of the O+H₂⁺ reaction.We study the stereo-dynamics of the reaction O + H₂⁺ at five collision energy Ecol= 0.2,0.4,0.6,0.8,1.0 eV using the QCT method.It has been found that the reaction probabilities and the reaction cross sections of the title reaction decrease monotonically with increasing the collision energy.Further,it is found that product OH+ exhibits a rather strong alignment perpendicular to the scattering z–x plane and a strong orientation pointing to the positive y-axis.The calculated polarization dependent differential cross sections（PDDCS）indicate that the products are mainly forward and backward scattering,and the product angular distributions are an-isotropic.In all cases,the title reaction is dominated by the direct reaction mechanism and the collision time becomes shorter with the increase of collision energy.In this work,the reaction O+H₂⁺（v=0-4,j=0-4）→OH⁺+H has been theoretically studied using quasi-classical trajectory（QCT）method at a collision energy of 0.2eV.Stereo-dynamics information was obtained for different initial rotational state ofreactant H₂⁺.The four normalized PDDCSs have been calculated and the results indicate the reaction mainly shows both forward and backward scattering.We can see that the product rotation angular momentum j’ is not only aligned but also oriented along the positive y-axis for the selected vibrational quantum number and rotation quantum number.Therefore we inferred that the reagent vibrational excitation has a positive influence on the polarization of the product rotational angular momentum,but rotation quantum number has the opposite effect.We have employed the quasi-classical trajectory method to study the vector correlation between the product and reagent for the three reactions of O+H₂⁺/ O+D₂⁺/ O+T₂⁺ on 12A’ PES constructed by Paniagua et al.The angle distribution functions、and four generalized polarization dependent differential cross sections（PDDCSs）are discussed in details.According to the results of the vector properties of the reactions,the pronounced isotopic effect is revealed.Isotopic effect has a negative influence on the polarization as is attributable to the different mass factors.