Resulting spectrum for different ALMA baseline selections, vertically offset for clarity, with, from top to bottom: all data and > 20 m, > 33 m, and > 50 m baselines. These limits correspond to minima in the visibility amplitudes. Only the spectrum based on the > 33 m limit exhibits a central dip at an S/N of ∼2, implying that this chosen limit has maximised any potential PH₃ signal.