The spectroscopic calculation can comprehensively validate the quality of PESs. Table and 2 display the bound states rotational energy levels of the corresponding inter-molecular ground states of para-and ortho-H 2 O-He, respectively, where the intramolecular vibration has been averaged to (v 1 , v 2 , v 3 ) = (0, 0, 0) state. The interaction between H 2 O and He is so weak that the high rotational excited states would close to the dissociation limit: 0.0 cm -1