<Li> Quadratic Stark broadening occurs via the quadratic Stark effect, which results from the interaction of an emitter with an electric field, causing a shift in energy that is quadratic in the field strength . (Δ E ∼ 1 / r 4) (\ displaystyle (\ Delta E \ sim 1 / r ^ (4))) </Li> <Li> Van der Waals broadening occurs when the emitting particle is being perturbed by van der Waals forces . For the quasistatic case, a van der Waals profile is often useful in describing the profile . The energy shift as a function of distance is given in the wings by e.g. the Lennard - Jones potential . (Δ E ∼ 1 / r 6) (\ displaystyle (\ Delta E \ sim 1 / r ^ (6))) </Li> <P> Inhomogeneous broadening is a general term for broadening because some emitting particles are in a different local environment from others, and therefore emit at a different frequency . This term is used especially for solids, where surfaces, grain boundaries, and stoichiometry variations can create a variety of local environments for a given atom to occupy . In liquids, the effects of inhomogeneous broadening is sometimes reduced by a process called motional narrowing . </P> <P> Certain types of broadening are the result of conditions over a large region of space rather than simply upon conditions that are local to the emitting particle . </P>

When are dark absorption lines produced from a star