Why LiCl acquires pink colour when heated in Li vapours?

Explanation

The `Cl^(-)` ions diffuse to the surface and form LiCl with `Li^(+)` ions. An electron is released `(Li to Li^(+) +e^(-))` which diffuses into the crystal and occupies the anionic site. Such anionic sites occupied with electrons are called F-centres. These impart pink colour to the crystal. The colour results by the excitation of the electrons on absorbing energy from visible light falling on the crystals.