https://doi.org/10.1351/goldbook.S05695
Oxygen molecule (dioxygen), O2, in an excited @[email protected] The @[email protected] of O2 is a triplet (\(^{3}\mathit{\Sigma} _{g}^{-}\)). The two @[email protected] singlet states derived from the ground-state configuration are \(^{1}\Delta _{g}\) and \(^{1}\mathit{\Sigma} _{g}^{+}\) (the latter with the higher energy).
Notes:
  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 \(^{1}\text{D}\) @[email protected] The oxygen atom @[email protected] 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. @[email protected] @[email protected] by triplet dioxygen (i.e., a process of @[email protected]) is the most common procedure for the production of singlet molecular dioxygen in solution. For many chemical species, the efficiency with which the @[email protected] is quenched by triplet dioxygen and, independently, the efficiency with singlet molecular dioxygen is produced, is controlled by the [email protected]@.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 420 [Terms] [Paper]