energyforbidden

Energyforbidden is a term used in some theoretical and educational discussions to refer to energy states or transitions that are not allowed under a given set of constraints. It is not a standardized scientific term with a fixed definition, and its exact meaning depends on the context in which it appears. In this sense, energyforbidden often serves as a shorthand for situations in which a particular energy change cannot occur through the dominant interaction or obey the primary selection rules.

In quantum mechanics, energyforbidden describes transitions that are prohibited by selection rules for a specific coupling, such as electric dipole transitions. When a transition is energyforbidden under the primary interaction, it can sometimes proceed via higher-order processes (for example, magnetic dipole or electric quadrupole interactions) but with greatly reduced probability. As a result, such transitions produce weak spectral lines and long-lived excited states, helping explain why certain energy changes are rare or effectively absent under ordinary conditions.

Beyond physics, energyforbidden may be used as a descriptive label in discussions of energy policy, security, or fictional narratives to indicate configurations, usages, or paths of energy that are restricted by rules, regulations, or design constraints. Because it is not a fixed term, practitioners typically define energyforbidden explicitly within their specific context to avoid ambiguity.