frequency, ν,ω in photochemistry

https://dx.doi.org/10.1351/goldbook.FT07383
The number of waveperiods per time interval. The linear frequency, ν, is the number of cycles per time interval. SI unit Hz = s −1.
Note:
For the angular frequency the symbol ω (= 2 π ν) is used with rad s −1 as the SI unit.
See also: a more general definition of frequency
Source:
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 345