Elastic scattering of two H(²S_g) and N(⁴S_u) atoms at low temperatures and accurate spectroscopic parameters of NH (X³\varSigma^-) radical

This paper reports that the interaction potential for the X³\varSigma^- state of NH radical is constructed at the CCSD(T)/ cc-PV6Z level of theory. Using this potential, this paper calculates the spectroscopic parameters (D_\rm e, R_\rm e, \omega_\rm e, \omega_\rm e\chi_\rm e, \alpha_\rm e and B_\rm e) and their values are of 3.578 eV, 0.10368 nm, 3286.833 cm^-1, 78.433 cm^-1, 0.6469 cm^-1 and 16.6735 cm^-1, respectively, which are in excellent agreement with the experiments. Then the total of 14 vibrational states has been found when J=0 by solving the radial Schrödinger equation of nuclear motion. For each vibrational state, the vibrational manifolds are reported for the first time. And last, the total cross sections, s-wave, p-wave and d-wave cross sections are computed for the elastic collisions between two ground-state atoms (hydrogen and nitrogen) at low temperatures. It finds that the total elastic cross sections are dominated by s-wave scattering when the collision energy is below 10^-6a.u. The pronounced shape resonance is found at energy of 6.1\times 10^-6a.u. Calculations have shown that the shape resonance comes from the p-wave contributions.