Talk:Wouthuysen–Field coupling

Coupling mechanism, 2nd paragraph
"'The coupling between Lyman-alpha photons and the hyperfine states depends not on the intensity of the Lyman-alpha radiation, but on the shape of the spectrum in the vicinity of the Lyman-alpha transition.'"

Surely this should be, "The coupling... depends not only on the intensity..." For example, Furlanetto, Peng and Briggs (2006) state that, "'The Wouthuysen-Field coupling must depend on the total rate (per atom) at which Lyα photons are scattered within the gas, $P_\alpha = 4\pi \chi_\alpha \int d\nu J_\nu(\nu) \phi_\alpha(\nu)$ where $\sigma_\nu = \chi_\alpha \phi_\alpha(\nu)$ is the local absorption cross section, $\chi_\alpha = (\pi e^2 / m_e c) f_\alpha$, $f_\alpha = 0.4162$ is the oscillator strength of the Lyα transition, $\phi_\alpha(\nu)$ is the Lyα absorption proﬁle, and $J_\nu$ is the angle-averaged speciﬁc intensity of the background radiation ﬁeld (by number, not energy)'"

This direct dependence on the specific intensity (spectral radiance if you like) seems to contradict the line above.--92.28.198.33 (talk) 23:10, 12 April 2017 (UTC)