How can electrical discharge through a low-pressure gas produce free radicals?

Electrical discharge through a low-pressure gas is a recognized method for generating free radicals, which are highly reactive atoms or groups of atoms containing one or more unpaired electrons.12

When an electric discharge is passed through a gas at low pressure, the energy provided by the discharge is sufficient to disrupt the chemical bonds within the gas molecules. This process causes the dissociation of molecules into smaller, highly reactive fragments—the free radicals.2

This technique is one of several established methods for producing unstable species in the gas phase, alongside photochemical decomposition and specific chemical reactions, such as those between sodium vapour and alkyl halides. Because these radicals are transient and short-lived, they are often studied by observing the specific chemical reactions they undergo, such as their ability to react with metal mirrors or participate in chain reactions.2