R Hya spectra of the F′ − F″ = 13−13 and 14−14 hyperfine transitions of OH in the υ = 0, J = 27/2 rotational transition (lines 1 and 2 in Table 3) extracted from combined high and mid spatial resolution data for an aperture diameter of 0.″08, 0.″16 and 0.″40. The spectra are converted from the observed frequency to the LSR frame using the line 2 rest frequency as the “reference” frequency. The black dotted vertical line (line 2) is at the adopted new systemic velocity (see Table 1). The green dotted vertical line is displaced by ~24.3 km s⁻¹ compared to line 2 as expected from the υ = 0, J = 27/2 Λ-doublet frequency separation; it corresponds to line 1.