Rotation diagram for CH₃OH lines in comet C/2004 Q2 (Machholz) including 1-σ uncertainties. The column density of the upper level divided by its degeneracy in logarithmic scale is plotted against the energy of the upper level. Filled (blue) circles are A and A-CH₃OH lines, empty (red) circles denote E-CH₃OH transitions and the empty (red) triangle indicates the 3-σ upper limit on the J = 7₄–6₄E transition at 338.530 GHz. The solid line shows the best linear fit with a derived rotational temperature of 85±7 K. The dashed line shows the best linear fit excluding the J = 13₁–13₀A transition at 342.730 GHz (energy of the upper state of  ~228 K relative to the ground state) with a derived rotational temperature of 40 ± 3 K.