Spectroscopy. Atoms and Light. Atomic electron energy levels are a source of discrete photon energies. Change from a high to low energy state produces a photon. Atoms can also absorb a photon to excite an electron. Discrete Spectrum. Each atom has its own set of energy levels.
Energy states in molecules contribute to stellar spectra.
Internuclear distances are quantized in discrete states.
Angular momentum for the molecule is quantized.
Atoms and molecules can reemit absorbed energy.
Fluorescence typically involves three steps.
Excitation to higher energy state.
Loss of energy through change in vibrational state
Emission of fluorescent photon.