The Collision Dynamics Studies Of He-CO(X~1?~+) System At Cold And Ultracold Temperatures

Weak interaction system has been an important research object in astrophysics and physical chemistry.In 2015,Astrid Bergeat et al reported their collision studies at the quantum state level published in Nature Chemistry(2015,7:349).Using cross molecular beam technique,they studied the quantum dynamic resonance in the inelastic j=0?j=1collision between He atom and CO(j=0)molecule at 4K.Based on the above experimental background,we will theoretically calculate the cold collision dynamics of He atom with CO molecule.It mainly includes the following contents:(1)Adopt the CCSDT(Q)method of iterative calculation of coupled cluster single and double triple excitation,quadruple excitation for perturbation processing,and select d-aug-cc-p VXZ(X=T,Q,5)basis set containing double spread function,the interaction potential energy of He-CO system is calculated by extrapolation schemes.The high precision two-dimensional potential energy surfaces of He-CO(v=0)and He-CO(v=1)systems are constructed using the theory of reproducing kernel Hilbert space(RKHS).The results show that:He-CO(v=0)has a potential well and the equilibrium position is at R=6.42 ₀,?=70.14°and the potential well is-22.39cm^-1.He-CO(v=1)also has a potential well and the equilibrium position is at R=6.43 ₀,?=69.79°,the potential well is-22.37cm^-1.The two-dimensional potential energy surfaces of v=0 and v=1 show weak anisotropy.(2)Based on the high precision potential energy surface,the bound energy levels of⁴He-CO and ³He-CO systems are calculated when the monomer CO molecule is in the vibrational state v=0.The results show that:there are 14 bound states in ⁴He-CO(v=0)and10 bound states in³He-CO(v=0).We further calculated the infrared transition frequencies of ⁴He-CO and ³He-CO systems in the molecular ground vibrational state of monomer CO.The root mean square difference is only 0.01cm^-1.The theoretical results are in good agreement with the experimental results,which also shows that the potential energy surface constructed in this work is accurate enough.(3)The cold collision dynamics of He-CO system at low rotational state are studied using quantum scattering method.The results show that:the elastic cross section tends to be constant with the decrease of energy,the inelastic cross section conforms to the expected behavior of Wigner threshold rule,and there are multiple resonance structures in the integral cross section.There are five obvious resonance peaks in the rotational excitation cross section of He+CO(j=0?1),and the positions of the resonance peaks calculated by the theory are basically consistent with the experimental results of Astrid Bergat et al.