Carbonberylliumlike

Carbonberylliumlike refers to atomic species that are isoelectronic with either carbon or beryllium, i.e., they have the same number of electrons as those neutral atoms: six for carbon-like and four for beryllium-like sequences. In practice, this means considering all ions and atoms that share the same electron configuration after accounting for the filled inner shells. The carbon-like sequence comprises ions with six electrons, typically described by a ground-state configuration close to [He] 2s2 2p2, while the Be-like sequence comprises ions with four electrons, near [He] 2s2. As the nuclear charge increases along either sequence, relativistic and quantum-electrodynamic effects become more pronounced, altering energy levels and transition probabilities.

Electronic structure and spectroscopy: In light systems, LS coupling provides a useful framework, with term symbols and level patterns resembling neutral carbon or beryllium. At higher atomic numbers, jj coupling and relativistic corrections become important, shifting energy levels and fine structure. The two sequences share similar valence-electron dynamics, which allows coordinated study of transitions, line strengths, and ionization behavior across a wide range of elements.

Applications: Carbon-like and Be-like ions are central in high-precision atomic spectroscopy, astrophysical plasma diagnostics, and fusion research. Their line spectra serve as benchmarks for atomic structure calculations and as probes of physical conditions such as temperature and density in plasmas.

Methods: Theoretical approaches include multiconfiguration Dirac-Hartree-Fock, relativistic configuration-interaction, and many-body perturbation theory. Experimentally, measurements often employ electron-beam ion traps, beam-foil spectroscopy, and x-ray or ultraviolet spectroscopy of highly charged ions.

In summary, carbonberylliumlike encompasses the isoelectronic families with six and four electrons, providing a structured framework for studying atomic structure and spectra across the periodic table.