Homogeneous cloud water models for different dust properties. Top left: R_gd = 100 and T_dust = T_kin∕2. Top right: R_gd = 100 and T_dust = 3T_kin∕2. Bottom left: R_gd = 50 and T_dust = T_kin∕2. Bottom right: R_gd = 200 and T_dust = T_kin∕2. Scales and contours are as in Fig. 13. In the 22 GHz maser case, intensity ratios, I₂₂ ∕I₅₅₇, are sometimes in excess of 10⁵ (central white areas). The strongest 22 GHz maser in these four cases occurs in the bottom left panel for T_kin = 700 K and n(H₂) = 10¹⁰ cm⁻³. Here the integrated intensity ratio is about 10⁷.