describes the disk parameters, such as the flux, $Q^-_{\rm rad}$, viscous heating, $Q^+_{\rm vis}$ (or $W$), disk height, $H$, central (mid-plane) density, $\rho_{\rm c}$, and optical depth, $\tau$.

[1]{} [20pc]{} [Opacities from Alexander et al. (1993), Cox and Stewart (1970), and Cox and Tabor (1976) for $\log\rho = -6.0$ to $-8.0$ at intervals of $\Delta\log\rho$ = 0.5.]{}

We have taken the opacity from Alexander et al. (1983) for low temperatures ($\log T_{\rm c}$ $\lta$ 4.0), and Cox and Stewart (1970) and Cox and Tabor (1976) for high temperatures ($\log T_{\rm c}$ $\gta$ 4.0) with mass fractions $X_{\rm H}$ = 0.71 and $X_{\rm He}$ = 0.27. The opacity for the intermediate temperature region is interpolated. The resultant opacity in the low-density region appropriate to our models in the outer disk is presented in figure 1, where the dominant effects are designated. We plot the opacity for $\log\rho_{\rm c}$ = $-$6 to $-$8. The disk regions in which we are interested have a density distribution of $\log {\rho}_{\rm c}$ = $-$6.2 to $-$7.7. The range, $\log T_{\rm c}$ $\sim$ 3.25–3.55, is the region dominated by molecular opacity. As shown in figure 1, the effect of molecules diminishes at $\log T_{\rm c}$ $\gta$ 