Non-optimized complex absorbing potentials for quantum resonances

Complex absorbing potentials represent a powerful tool for the investigation of quantum resonances. However, they have to be carefully chosen for each physical situation. The purpose of this Letter is to show that non-optimized complex potentials can be used within the general framework of perturbation theory. The procedure is widely independent of the particular form of the absorbing potential at the expense of dealing with higher-order perturbation expansions. Its efficiency is demonstrated on the multichannel vibronic predissociation of the LiH molecule.