We report an ab initio intermolecular potential energy surface calculation on the He-N2O complex with N2O 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 He-4-N2O and He-3-N2O with N2O 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 He-4-N2O and He-3-N2O, respectively. Moreover, the calculations on the line intensities of the rotational transitions in the v(3) region of N2O for the ground vibrational state shows that the He-3-N2O spectrum is dominated by a-type transitions (DeltaK(a) = 0), while the He-4-N2O spectrum is contributed by both the a-type and b-type (DeltaK(a) = +/-1) transitions. The calculated transition frequencies and the intensities are in good agreement with the observed results. (C) 2004 American Institute of Physics.