Expected line intensities for the two strongest series of hyperfine lines for a cold prestellar core with a column density N(CH₂OH) = 10¹² cm^-2, full line width at half power Δv = 1 km s^-1, and T_K = 12 K. The predictions have been obtained with the MADEX code (Cernicharo 2012). The upper panel corresponds to the fundamental R-branch transition 1₁₁−0₀₀ around 220.5 GHz and the lower one to the Q-branch transition 1₁₀−1₀₁ near 168.6 GHz. Quantum numbers for the selected hyperfine components can be found in Table 6. We have assumed that the source fills the main beam of the telescope.