An element can produce laser when it is in which state?

An element can produce laser light when it is in the metastable state. In this state, atoms are able to maintain their energy levels for a longer duration compared to other states. This extended lifetime of the excited state is crucial for the process of stimulated emission, which is the fundamental mechanism behind laser operation.

When an atom is excited, it absorbs energy and moves to a higher energy level. If this excited state quickly transitions back to a lower energy level, the process will not effectively contribute to laser action. In the metastable state, the atoms can accumulate a certain population of excited particles because they do not return to their ground state immediately. This population inversion is essential for creating the necessary conditions for laser action, as it allows for more stimulated emissions than spontaneous emissions to occur, leading to the amplification of light.

When discussing other states, the stable state typically refers to configurations where atoms do not have enough energy for laser activity, while the ground state means the atoms are at their lowest energy level, so laser production is not possible. Therefore, only the metastable state allows for the effective buildup of excited particles needed to achieve the necessary conditions for laser emission.