Electron Excitation by Collisions

When gas particles collide with electrons if there is not enough energy for ionisation at certain energies excitation occurs.If no excitation, then the particles are deflected with no loss of kinetic energy.The excitation energy is the energy at which an atom absorbs energy e.g. mercury absorbs photons of 4.9 eV and 6.7 eVThe electron moves from an inner shell to a higher energy outer shell. The lowest energy state is called the ground state.Electrons absorb energy and move to a higher energy shell.The atom is in an excited state.