An earlier work of Dolmatov et al. [Phys. Rev. A 73, 013201 (2006)] on Ne inside a charged fullerene ($\mathrm{Ne}@{\mathrm{C}}_{60}^{\mathrm{q}=-3,-5}$) has revealed the presence of two unusually large confinement resonances termed Coulomb confinement resonances (CCRs); the first CCR is narrow and the second one is broad and their origins are attributed to the presence of charge on the fullerene surface. The present work extends this study to other subshells and also to other systems such as $\mathrm{Ar}@{\mathrm{C}}_{60}^{\mathrm{q}}$ and $\mathrm{Xe}@{\mathrm{C}}_{60}^{\mathrm{q}}$ using relativistic random phase approximation, but with an aim to investigate the genesis of the CCRs. Further, a detailed analysis of these resonances within a single active electron approximation unearths an interesting difference associated with the origin of these two CCRs. The photoionized electron is temporally trapped in the ${\mathrm{C}}_{60}$ confinement well for the case of narrow resonance and in the atomic well region for the case of broad resonance. Also, the present work shows that the broad resonance can occur even for the case of $q=0$ and is demonstrated for $\mathrm{Xe}@{\mathrm{C}}_{60}^{\mathrm{q}}$ as a test case.

• Received 6 July 2020
• Revised 16 October 2020
• Accepted 2 December 2020

DOI:https://doi.org/10.1103/PhysRevA.102.062826