Parameters from NH₃ analysis: (1,1) line width and rotational temperature as a function of NH₃ and N₂H⁺ deuterium fractionation. The legend is the same as in Fig. 5. The square marks denote the stronger component, the circle the weaker component of the source. For NH₃ deuteration, we see no correlation between the parameters. For N₂H⁺ deuteration, we see a correlation between the evolutionary phase of the sources and the rotational temperature.