Product of the @[email protected] by the @[email protected], \(\sigma \ \varPhi \). SI unit is \(\text{m}^{2}\); commonly expressed in \(\text{cm}^{2}\).
Source: PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 318 [Terms] [Paper]