Investigation of spectroscopic characteristics and photoelectron angular distributions for photoionization of H@ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg" display="inline" id="d1e1594"> <mml:msub> <mml:mrow> <mml:mi>C<

This manuscript presents a comprehensive study on the spectral properties and photoionization dynamics of atoms encapsulated by fullerene cages, specifically focusing on a hydrogen atom encapsulated in a C 36 fullerene. For this objective, we use a comprehensive relativistic methodology, leveraging the Dirac–Coulomb Hamiltonian in a relativistic configuration interaction scheme, incorporating a power-exponential potential to simulate the fullerene cage’s confining effect. By incorporating the Gaussian potential, the Dirac equation is modified to provide solutions covering both continuous and bound state wave functions. As a case study, thorough investigations are performed on the changes in energies, transition rates, wave functions, photoionization cross sections, and photoelectron angular distribution parameters for the hydrogen atom inside a C 36 fullerene cage. We perform a detailed analysis, compare our results with other available data, and find good agreement. This study is not only important in the field of atomic physics and quantum chemistry but also offers insights into the design of nanocomposite materials and the development of optical materials and photonic devices. • The photoionization of H@C36 is studied. • The method within the relativistic Dirac–Coulomb scheme is suggested. • This work offers insights into the design of nanocomposite materials.