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Understanding the processes that can destroy H$_2$ and H$^-$ species isquintessential in governing the formation of the first stars, black holes andgalaxies. In this study we compute the reaction rate coefficients for H$_2$photo--dissociation by Lyman--Werner photons ($11.2 - 13.6$ eV), and H$^-$photo--detachment by 0.76 eV photons emanating from self-consistent stellarpopulations that we model using publicly available stellar synthesis codes. Sofar studies that include chemical networks for the formation of molecularhydrogen take these processes into account by assuming that the source spectracan be approximated by a power-law dependency or a black-body spectrum at10$^4$ or $10^5$ K. We show that using spectra generated from realistic stellarpopulation models can alter the reaction rates for photo-dissociation, $\rmk_{\rm{di}}$, and photo-detachment, $\rm k_{\rm{de}}$, significantly. Inparticular, $\rm k_{\rm{de}}$ can be up to $\sim 2-4$ orders of magnitude lowerin the case of realistic stellar spectra suggesting that previous calculationshave over-estimated the impact that radiation has on lowering H$_2$ abundances.In contrast to burst modes of star formation, we find that models withcontinuous star formation predict increasing $\rm k_{\rm{de}}$ and $\rmk_{\rm{di}}$, which makes it necessary to include the star formation history ofsources to derive self-consistent reaction rates, and that it is not enough tojust calculate J$_{21}$ for the background. For models with constant starformation rate the change in shape of the spectral energy distribution leads toa non-negligible late-time contribution to $\rm k_{\rm{de}}$ and $\rmk_{\rm{di}}$, and we present self-consistently derived cosmological reactionrates based on star formation rates consistent with observations of the highredshift Universe.

Revised rate coefficients for H$_2$ and H$^-$ destruction by realistic stellar spectra