Oxygen excited helium with

Chemiluminescent Reactions of Excited Helium with Nitrogen and Oxygen... 

Table I. Rate Constants and Diffusion Coefficients for the Reactions of Excited Helium with Nitrogen and Oxygen...

The analogy is even closer when the situation in oxygen is compared with that in excited configurations of the helium atom summarized in Equations (7.28) and (7.29). According to the Pauli principle for electrons the total wave function must be antisymmetric to electron exchange. 

The rate constant for the reaction of ethyl radicals and oxygen increases with the increasing concentration of inert helium [57]. This indicates the possible participation of the molecules in the process of stabilization of peroxy radicals formed. The excited alkyl peroxy radicals do not fragmentate only to original reactants but rearrange to products through separate pathways [58]. 

The presence of oxygen is critical because the interaction of oxygen with the sample can cause serious errors, and its ability to quench not only the fluorescence but also phosphorescence makes deaeration necessary. Also, the photoluminescence intensity usually decreases when the temperature of the sample is increased this is attributed to the higher probability for other nonradiative deactivations in the excited state of the molecule. Therefore, to minimize such temperature effects, the photoluminescence spectra are often measured at liquid-nitrogen temperature and even liquid-helium temperature (33, 34, 36-38, 49-53). 

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