Constant ALPHA_RHO

pub const ALPHA_RHO: f64 = _; // 0.37020884510871604f64

α_ρ = G₂/G₃ — ratio of photon number to energy spectral integrals.

This constant determines the critical frequency x₀ = 4/(3α_ρ) at which photon injection produces zero μ-distortion. Below x₀, injection produces negative μ; above x₀, positive μ.

Reference: Chluba (2015), arXiv:1506.06582, Eq. 30