C18O
C¹⁸O ground state rotational frequencies calculated and published in 2003 ApJ 592, L95 by G. Cazzoli, C. Puzzarini, and A. V. Lapinov.
J_up J_low Freq_cal(MHz) sig(m/s) 1 - 0 109782.17580(15) 0.40 2 - 1 219560.35782(26) 0.36 3 - 2 329330.55237(33) 0.30 4 - 3 439088.76600(34) 0.24 5 - 4 548831.00557(40) 0.22 6 - 5 658553.27839(64) 0.29 7 - 6 768251.5923(11) 0.42 8 - 7 877921.9559(17) 0.58 9 - 8 987560.3783(24) 0.73 10 - 9 1097162.8698(32) 0.88 11 - 10 1206725.4415(41) 1.01 12 - 11 1316244.1056(48) 1.10 13 - 12 1425714.8755(55) 1.16 14 - 13 1535133.7661(60) 1.18 15 - 14 1644496.7934(64) 1.17 16 - 15 1753799.9752(69) 1.18 17 - 16 1863039.3309(81) 1.30 18 - 17 1972210.881(11) 1.62 19 - 18 2081310.650(15) 2.21 20 - 19 2190334.661(22) 3.06 21 - 20 2299278.942(32) 4.19 22 - 21 2408139.523(45) 5.60 23 - 22 2516912.433(61) 7.31 24 - 23 2625593.708(82) 9.35 25 - 24 2734179.384(107) 11.74