Same cloud as Fig. 17, with formation parameter R_f for the LH mechanism, comparing standard (dashed black) and coupled (solid black) models. The insets show the effect of fluctuations on a 1 nm grain at the two positions in the cloud marked by the arrows. Blue: temperature PDF, red: equilibrium temperature, dashed green: equilibrium efficiency, and solid green: conditional efficiency with fluctuations. See the text for more details.