Energy loss for electrons in water vapor at 300 K for electron energies between 0.2 and 20 eV. Panel a: energy loss function. Panel b: electron energy as function of column density from the starting point for various initial energies. Panel c: electron energy as function of distance for electrons starting at the nucleus with various initial energies for three values of the production rate Q. Rotationalloss is approximated by Eq. (6). Vibrational loss is calculated from Eq. (11) of Cravens & Körösmezey (1986) with cross sections from Table 9 of Itikawa & Mason (2005). The vibrational loss reaches zeroat the lowest threshold energy of 0.198 eV.