Section of the millimeter-wave spectrum of n-C₄H₉CN displaying features caused by all three conformers investigated in the present analysis. The quantum numbers for the J = 38−37 transitions of the AA conformer are given in blue (the K_c quantum numbers have been omitted because the asymmetry splitting was not resolved for these transitions). Transitions of the GA and AG conformers have been marked with triangles pointing upward (green) and downward (red), respectively. Triangles in parentheses are used for overlapped lines or lines with bad line shape. The AG lines have J = 34−33, and K_a = 27, 4, and 28 from left to right; K_c = J − K_a + 1 for the K_a = 4 line. The GA lines belong to b-type Q-branch transitions with quantum numbers J_Ka,Kc = 40_9,31−40_8,32, 69_7,62−69_6,63, and 95_11,84−95_10,85 from left to right. The lines are presented as second derivatives of a Gaussian line shape because of the 2f-modulation.