J-Matrix approach for the exponential-cosine-screened Coulomb potential

The bound state energies for the exponential-cosine-screened Coulomb potential were calculated by using the Gauss quadrature method. The resonance energies were calculated using the complex rotation method and were then used as a seed for our J-matrix approach in order to achieve improved results. The calculated bound and resonance state energies are compared with the available numerical data in this paper. The trajectories of the resonance states in the complex E-plane are also shown. New data, for both bound and resonance state energies close to the crossover region of the transition from bound to resonance, have been reported for guiding future studies.