This is the published version, also available here: http://dx.doi.org/10.1063/1.442929.The complex‐coordinate coupled‐channel (CCCC) formalism previously developed [J. Chem. Phys. 72, 4772 (1980)] is applied to the accurate determination of the level widths (lifetimes) and energies of rotationally predissociating metastable Ar⋅⋅⋅H2 van der Waals molecules. Calculations are performed using several realistic anisotropic potentials obtained recently by experiments, including Lennard‐Jones (LJ), Buckingham–Corner (BC) type potentials, as well as the semiempirical potential of Tang–Toennies (TT). New numerical methods are introduced here to deal with the complex rotations of piecewise inhomogeneous potentials such as those of BC and TT. It is found that the CCCC method is capable of providing reliable results for any given potential surface. Furthermore, the CCCC results are sensitive to the potential surfaces used. For example, the linewidths predicted for different LJ potential surfaces considered here vary by a factor as large as 4. However, the agreement among more recent potentials, namely, the BC potential of Zandee and Reuss and that of Le Roy and Carley as well as the potential of Tang and Toennies, is much closer: the resonance energies agree to within 1 cm−1 and the linewidths to within 30%
