https://doi.org/10.1351/goldbook.14039
Ratio of the number of photoadsorbed entities \(\ce{B}\) (molecules, atoms, or ions) on a surface to the number of photons of ultraviolet, visible, or infrared radiation (at a given wavelength \(\lambda\)) absorbed by the system (typically by the adsorbent) during the initial stage of irradiation.
Note: Mathematical expression: \(\mathit{\Phi}_{\rm{ads}} = \frac{{\rm{d}}N_{\ce{B}}/{\rm{d}}t}{{\rm{d}}N_{\rm{p},\lambda}/{\rm{d}}t}\), for \(t \to 0\), i.e., the ratio of the initial rates of photoadsorption and monochromatic photons absorbed, with \(N_{\ce{B}}\) the number of entities adsorbed and \(N_{\rm{p},\lambda}\) the number of photons of wavelength \(\lambda\) absorbed. The photoadsorption quantum yield has been called \(K_{\rm{a}}\).