For reaction (5.18) it has been shown from a crossed molecular beam experiment that the main process is CH2OH + H, and the process of CH3O + H is not important (Lin et al., 1998). Also for the physical deactivation pathway (5.20), Wine and Ravishankara (1982) and Takahashi et al. (1996) reported that the ratio is less than a few%, while the recent high precision experiment of Vranckx et al. (2008b) by using the chemiluminescence method showed that it is 0.20.3% and that it is negligible as an atmospheric reaction.