Oxygen molecule (dioxygen), O2, in an excited @S05699@. The @G02704@ of O2 is a triplet (\(^{3}\mathit{\Sigma} _{g}^{-}\)). The two @M03872@ singlet states derived from the ground-state configuration are \(^{1}\Delta _{g}\) and \(^{1}\mathit{\Sigma} _{g}^{+}\) (the latter with the higher energy).
  1. Use of the term singlet oxygen alone, without mention of the chemical species is discouraged since it can also refer to an oxygen atom in a \(^{1}\text{S}\) or \(^{1}\text{D}\) @E02257@. The oxygen atom @G02704@ is a triplet \(^{3}\text{P}\) state and the \(^{1}\text{S}\) and \(^{1}\text{D}\) states are also derived from the ground-state configuration.
  2. @T06503-1@ @Q05007@ by triplet dioxygen (i.e., a process of @P04652@) is the most common procedure for the production of singlet molecular dioxygen in solution. For many chemical species, the efficiency with which the @T06503-2@ is quenched by triplet dioxygen and, independently, the efficiency with singlet molecular dioxygen is produced, is controlled by the spin-@R05175@.
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 420 [Terms] [Paper]