Ionisation & Excitation
- Ionisation of an atom is:
The removal of an electron from an atom, from the electron's ground state
- Excitation of electrons is:
When an electron is given enough energy to move up an energy level, but not enough to leave the atom
Fluorescent Tube
- Fluorescence occurs when an electron in an atomic orbital absorbs energy from an interaction with a photon or a collision with another atom
- Fluorescent tubes are partially evacuated glass tubes filled with low-pressure mercury vapour with a phosphor coating on the glass
- When a high voltage is applied across the vapour, the electrons in mercury are excited and move to a higher energy level
- This high energy level state is unstable and so the electron moves back to its original state, or de-excites
- As it de-excites, the electron releases some of that energy in the form of a UV photon
- This UV light then excites the electrons in the phosphor coating
- As a result, visible light photons are released when the electrons return to their original energy state, which provides the fluorescent glow
Fluorescent tubes operate on the basis of excitation and de-excitation of electrons leading to the emission of visible light
