Astronomy & Astrophysics

$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig1.eps}\end{figure}$ Figure 1: Steady-state abundances of major ions and electrons in the standard model ( $a_{\rm g}$ = 0.1 $\mu$ m, T = 10 K, $\zeta = 3$ $\times$ 10^-17 s^-1) as functions of the density of molecular hydrogen.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig2.eps}\end{figure}$ Figure 2: Steady-state values of the para/ortho D₂ and D₂H⁺ ratios and the meta/ortho D₃⁺ ratio, as functions of the molecular hydrogen density ( $a_{\rm g}$ = 0.1 $\mu$ m, T = 10 K, $\zeta = 3$ $\times$ 10^-17 s^-1).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig3.eps}\end{figure}$ Figure 3: Steady-state fractional abundances of HD and D₂, as functions of the molecular hydrogen density. The fractional abundances of atomic H and D are also plotted ( $a_{\rm g}$ = 0.1 $\mu$ m, T = 10 K, $\zeta = 3$ $\times$ 10^-17 s^-1).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig4.eps}\end{figure}$ Figure 4: The ratio n(H₂D⁺)/n(H₃⁺), computed for $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3 and $a_{\rm g} = 0.1$ $\mu$ m, as a function of the gas kinetic temperature, T. The value of the ratio in LTE is also plotted.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1464fig5.eps}\end{figure}$ Figure 5: The the para/ortho D₂H⁺ and meta/ortho D₃⁺ ratios, computed for $n({\rm H_2}) = 10^6$ cm^-3 and $a_{\rm g} = 0.1$ $\mu$ m, as functions of the gas kinetic temperature, T. The values of the ratios in LTE are also plotted.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1464fig6.eps}\end{figure}$ Figure 6: The the ortho/para H₃⁺ and H₂D⁺ ratios, computed for $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3 and $a_{\rm g} = 0.1$ $\mu$ m, as functions of the gas kinetic temperature, T. The values of the ratios in LTE are also plotted.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig7.eps}\end{figure}$ Figure 7: The ratio n(para-D₂H⁺)/n(ortho-H₂D⁺), computed for $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3 and $a_{\rm g} = 0.1$ $\mu$ m, as a function of the gas kinetic temperature, T. (Vastel et al. (2004) have reported a value of 0.75 for this ratio in the prestellar core 16293E (see text, Sect. 3.2).)
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig8.eps}\end{figure}$ Figure 8: The fractional abundances of the major ions and the free electron abundance plotted against the grain radius, $a_{\rm g}$ , for a density of $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3, T = 10 K, and $\zeta = 3$ $\times$ 10^-17 s^-1.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig9.eps}\end{figure}$ Figure 9: The ortho/meta ratio of D₃⁺ and the ortho/para ratios of D₂H⁺ and D₂ plotted against the grain radius, $a_{\rm g}$ , for a density of $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3, T = 10 K, and $\zeta = 3$ $\times$ 10^-17 s^-1.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig1.eps}\end{figure}$	Figure 1: Steady-state abundances of major ions and electrons in the standard model ( $a_{\rm g}$ = 0.1 $\mu$ m, T = 10 K, $\zeta = 3$ $\times$ 10^-17 s^-1) as functions of the density of molecular hydrogen.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig2.eps}\end{figure}$	Figure 2: Steady-state values of the para/ortho D₂ and D₂H⁺ ratios and the meta/ortho D₃⁺ ratio, as functions of the molecular hydrogen density ( $a_{\rm g}$ = 0.1 $\mu$ m, T = 10 K, $\zeta = 3$ $\times$ 10^-17 s^-1).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig3.eps}\end{figure}$	Figure 3: Steady-state fractional abundances of HD and D₂, as functions of the molecular hydrogen density. The fractional abundances of atomic H and D are also plotted ( $a_{\rm g}$ = 0.1 $\mu$ m, T = 10 K, $\zeta = 3$ $\times$ 10^-17 s^-1).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig4.eps}\end{figure}$	Figure 4: The ratio n(H₂D⁺)/n(H₃⁺), computed for $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3 and $a_{\rm g} = 0.1$ $\mu$ m, as a function of the gas kinetic temperature, T. The value of the ratio in LTE is also plotted.
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1464fig5.eps}\end{figure}$	Figure 5: The the para/ortho D₂H⁺ and meta/ortho D₃⁺ ratios, computed for $n({\rm H_2}) = 10^6$ cm^-3 and $a_{\rm g} = 0.1$ $\mu$ m, as functions of the gas kinetic temperature, T. The values of the ratios in LTE are also plotted.
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1464fig6.eps}\end{figure}$	Figure 6: The the ortho/para H₃⁺ and H₂D⁺ ratios, computed for $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3 and $a_{\rm g} = 0.1$ $\mu$ m, as functions of the gas kinetic temperature, T. The values of the ratios in LTE are also plotted.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig7.eps}\end{figure}$	Figure 7: The ratio n(para-D₂H⁺)/n(ortho-H₂D⁺), computed for $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3 and $a_{\rm g} = 0.1$ $\mu$ m, as a function of the gas kinetic temperature, T. (Vastel et al. (2004) have reported a value of 0.75 for this ratio in the prestellar core 16293E (see text, Sect. 3.2).)
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig8.eps}\end{figure}$	Figure 8: The fractional abundances of the major ions and the free electron abundance plotted against the grain radius, $a_{\rm g}$ , for a density of $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3, T = 10 K, and $\zeta = 3$ $\times$ 10^-17 s^-1.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1464fig9.eps}\end{figure}$	Figure 9: The ortho/meta ratio of D₃⁺ and the ortho/para ratios of D₂H⁺ and D₂ plotted against the grain radius, $a_{\rm g}$ , for a density of $n_{\rm H} = 2$ $\times$ 10⁶ cm^-3, T = 10 K, and $\zeta = 3$ $\times$ 10^-17 s^-1.
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