Nonhydrogenic

Nonhydrogenic refers to atomic systems that are not hydrogenic. A hydrogenic atom or ion consists of a nucleus and a single electron. Examples include the neutral hydrogen atom (one proton, one electron) and ions like helium ion (He+) (a helium nucleus, two protons, and one electron) or lithium ion (Li2+) (a lithium nucleus, three protons, and one electron).

In contrast, nonhydrogenic systems involve atoms or ions with multiple electrons orbiting the nucleus. These systems are significantly more complex to model and understand due to electron-electron interactions. These interactions, often referred to as electron correlation, lead to deviations from the simple, analytical solutions possible for hydrogenic systems.

The electronic structure of nonhydrogenic atoms is typically studied using computational quantum chemistry methods. These methods approximate solutions to the Schrödinger equation for systems with more than one electron. Concepts like orbitals, energy levels, and spectral lines are still relevant, but their precise values and behaviors are modified by the presence of other electrons. Understanding nonhydrogenic systems is crucial in various fields, including atomic physics, spectroscopy, and astrophysics, where such systems are abundant.