Oh-Production

Tropospheric OH radical production from O₃ photolysis — Seinfeld & Pandis (2006) Ch. 6 §6.1 Eqs. 6.1, 6.3, 6.4, pp. 204-207. The dominant source of OH in the troposphere is O₃ photolysis below 320 nm producing electronically excited O(¹D), which either reacts with H₂O to yield two OH radicals or is collisionally quenched back to ground-state O(³P) by N₂/O₂. Implements three algebraic relations: (Eq. 6.1) O(¹D) steady-state concentration [O(¹D)] = j_O₃·[O₃] / (k₃[M] + k₄[H₂O]), (Eq. 6.4) OH yield ε_OH = 2·k₄[H₂O] / (k₃[M] + k₄[H₂O]) as the fraction of O(¹D) producing OH (the factor of 2 accounts for the 2 OH produced per O(¹D)+H₂O encounter — ε_OH ranges 0..2), (Eq. 6.3) OH production rate P_OH = j_O₃·[O₃]·ε_OH. The effective quenching rate k₃_eff = f_N₂·k₃,N₂ + f_O₂·k₃,O₂ is the air-composition-weighted average of the N₂ and O₂ quenching channels. Observed-only algebraic system (no time derivatives): six variables (three inputs O₃/H₂O/M as parameters, three outputs O₁D/ε_OH/P_OH as state) plus six rate-parameter inputs (j_O₃, k₃_N₂, k₃_O₂, k₄, f_N₂, f_O₂) and one stoichiometric constant (two=2). Migrated from GasChem.jl@8c12c048 src/oh_production.jl:88 (`OHProduction` @component).