Referred to @A00087@ based on spectrophotometric measurements, \(S_{\text{ac}}\left(\lambda \right)=\varPhi \left(\lambda \right)\ \varepsilon\left(\lambda _{\text{obs}}\right)=\text{sensitivity or actinometric factor}\). \(\varPhi \left(\lambda \right)\) is the @Q04991@ of the @A00087@ at the excitation @W06659@ and \(\lambda _{\text{obs}}\) is the observation @W06659@, which may be the same as or differ from the former.