Rotational diagrams toward the MF3 peak based only on data observed with a beam of 1.79″  ×  0.79″ (top) and a beam of 3.63″  ×  2.26″ (bottom). Dots and squares with error bars mark detected and partially blended lines in the fundamental and first excited states v_t = 0 and v_t = 1, respectively. Filled triangles mark undetected lines and open triangles blended lines. The red line is the fit according to the method described in Sect. 4. The derived rotational temperatures are 85  ±  3 K and 103  ±  3 K, respectively.