isolatedatom
An isolated atom is a single atom that experiences negligible interactions with other atoms, molecules, or solid surfaces. In practice this condition is approximated when an atom is in the gas phase at low density, inside an ultrahigh vacuum, or confined in a trap or lattice where external perturbations are minimized. The term is often used in contrast to atoms that participate in chemical bonds in molecules or solids.
The physics of an isolated atom is governed by the electronic Hamiltonian of a single nucleus and
Isolated atoms are produced and studied in a variety of ways: effusive atomic beams, ovens, laser cooling
However, truly isolated atoms are an idealization. In practice, residual gas collisions, electromagnetic fields (Stark, Zeeman),