Phosphorus molecule , excited, from

Additionally, Figure 6.4 shows the variation in the energy of the occupied 5d orbitals when the P-Au-P angle varies from 180° (linear coordination) to 120°. Thus, while the dzi orbital stabilizes slightly, the dxz destabilizes as a consequence of the interaction of this orbital with the 3px and 3pz orbitals of phosphorus. The main consequence is that, below 168°, the former HOMO (dz2 in linear molecules) is replaced by the dxz orbital, which displays a higher energy and, consequently, a lower energy is needed to reach the excited state. 

The emission of fight observed by Brand was actually chemiluminescence. The fight arises from PO2 molecules in an excited state. This excited state of PO2 is brought about by the reaction between PO and ozone, which are both intermediates in the fundamental reaction between oxygen in air and P4 vapor evaporating from the solid white phosphorus. It is unfortunate that the chemiluminescent glow of phosphorus gave rise to the term... 

Diphosphorus P2 molecules are the primary species evaporating from red phosphorus, but are stable only at high temperatures or low pressures (Chapter 4.1). Various unstable ion fragments P2 P3 P4 P8 P P4 P P2 etc. are obtained by electron bombardment of red phosphorus in a mass spectrometer. Positive ion fragments are also obtained by arc or spaik excitation of red phosphorus. 

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