The role of resonant states in the process of merging bound states into continuum

The main properties of resonant states in continuum such as conditions of the appearance, the jump of the phase of wave function, the contribution of resonances to the density of states and dependence of the density of resonant states over the potential parameters are considered. It was demonstrated that in the region of the electron transition from discrete spectrum to continuum the contribution of resonance in the density of states is similar to the contribution on of corresponding bound level. It results in a conclusion about smooth behavior of thermodynamic quantities during pressure ionization.