Asymptotically vanishing PT-symmetric potentials and negative-mass Schroedinger equations

In paper I [M. Znojil and G. L'evai, Phys. Lett. A 271 (2000) 327] we introduced the Coulomb - Kratzer bound-state problem in its cryptohermitian, PT-symmetric version. An instability of the original model is revealed and its necessary stabilization is achieved, for almost all couplings, by an unusual, negative choice of the bare mass in Schroediner equation.