& $1.71\times 10^{-10}$\
50 & $1.67\times 10^{-10}$ & $1.72\times 10^{-10}$\
100 & $1.70\times 10^{-10}$ & $1.74\times 10^{-10}$\
1000 & $1.79\times 10^{-10}$ & $1.87\times 10^{-10}$\
\
\
\
$T_{\rm bb}$(K) & & $\mathrm{{}^{14}N{}^{15}N}$\
\
4000 &$2.35\times 10^{-16}$ & $2.44\times 10^{-16}$\
6000 &$1.04\times 10^{-13}$ & $1.07\times 10^{-13}$\
8000 &$1.95\times 10^{-12}$ & $2.01\times 10^{-12}$\
10000 &$1.05\times 10^{-11}$ & $1.08\times 10^{-11}$\
20000 &$1.98\times 10^{-10}$ & $2.02\times 10^{-10}$\

The term $\exp\left( -\gamma_\mathrm{dust} A_V \right)$ in Eq. (\[eq:def shielding function\]) describes shielding of the UV flux by dust grains, where the visual (5500Å) extinction is assumed proportional to the column density of hydrogen nuclei, $N_\mathrm{H}$, according to $A_V = N_\mathrm{H}/1.6\times 10^{21}$ [@savage1977]. In principle, this is a wavelength dependent quantity which depends on the distribution of dust grain sizes, their composition, and their geometries. The use of a simple parameterisation of declining intensity with increasing visual extinction is warranted by the significant uncertainties in these parameters. Radiative transfer calculations considering the destruction and scattering of photons by a realistic distribution of interstellar dust grains were made by @roberge1981 [@roberge1991]. The ultraviolet extinction relevant to various molecules was parameterised by @van_dishoeck2006 as a decaying exponential like that in Eq. (\[eq:def shielding function\]) using the the dust optical 