Hydrogen is the most abundant element. When a neutral hydrogen atom gets blasted with energy, its electron can be boosted to a larger orbit with a higher energy level. Then the electron can jump from one orbit level to another, which produces a photon. When the electron moves to the inner-most orbit from the orbit directly adjacent, it emits a photon with a particular wavelength in the ultraviolet spectrum, called Lyman-alpha emission. Since Lyman-alpha...
