The red glow is caused by the formation and decay of singlet O 2 .
Singlet oxygen is an excited form of oxygen.
Oxygen normally has two unpaired electrons in its outermost orbital. Upon receiving this exitation, the two electrons occupy a single molecular orbital. Two singlet oxygens go to the ground state by a two molecule, one photon transition. This is actually a form of radioactive decay, and it causes the red glow.