Intermolecular potential energy surface and rovibrational spectra of the He-N_2O complex from ab initio calculations

摘要

We report an ab initio intermolecular potential energy surface calculation on the He-N_2O complex with N_2O at its ground state using a supermolecular approach.The calculation was performed at the coupled-cluster [CCSD(T)] level,with the full counterpoise correction for the basis set superposition error and a large basis set including midpoint bond functions.The CCSD(T) potential is found to have two minima corresponding to the T-shaped and linear He-ONN structures.The T-shaped minimum is the global minimum.The two-dimensional discrete variable representation method was employed to calculate the rovibrational energy levels for ~4He-N_2O and ~3He-N_2O with N_2O at its ground and v_3 excited states.The results indicate that the CCSD(T) potential supports five and four vibrational bound states for the ~4He-N_2O and ~3He-N_2O,respectively.Moreover,the calculations on the line intensities of the rotational transitions in the v_3 region of N_2O for the ground vibrational state shows that the ~3He-N_2O spectrum is dominated by alpha-type transitions (DELTAK_(alpha)=0),while the ~4He-N_2O spectrum is contributed by both the alpha-type and b-type (DELTAK_(alpha)=+-l) transitions.The calculated transition frequencies and the intensities are in good agreement with the observed results.