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IAU list of important spectral lines

Astrophysics (I)

At the XXIst General Assembly of the International Astronomical Union, IAU, (Buenos Aires, 23 July - 1 August 1991) the astrophysically most important spectral lines have been carefully reviewed.

IAU listed the revision of these spectral lines as reproduced below and expressed the need to protect these frequency bands from in-band, band-edge and harmonic emissions, especially from space-borne transmitters.

To read : Molecules in Space, U.Koln, 2019

List of interstellar and circumstellar molecules, Wikipedia

Astrophysically most important spectral lines

Substance

Rest Frequency

Suggested

minimum bandwidth

Notes

Deuterium (DI)

 327.384 MHz 327.0 - 327.7 MHz 

Hydrogen (HI)

 1420.406 MHz 1370.0 - 1427 MHz 2),3) 

Hydroxyl radical (OH)

 1612.231 MHz 1606.8 - 1613.8 MHz 3),4) 

Hydroxyl radical (OH)

 1665.402 MHz 1659.8 - 1667.1 MHz 4) 

Hydroxyl radical (OH)

 1667.359 MHz 1661.8 - 1669 MHz 4) 

Hydroxyl radical (OH)

 1720.53 MHz 1714.8 - 1722.2 MHz 3),4) 

Methyladyne (CH)

 3263.794 MHz 3252.9 - 3267.1 MHz 3),4) 

Methyladyne (CH)

 3335.481 MHz 3324.4 - 3338.8 MHz 3),4) 

Methyladyne (CH)

 3349.193 MHz 3338.0 - 3352.5 MHz 3),4) 

Formaldehyde (HCHO)

 4829.66 MHz 4813.6 - 4834.5 MHz 3),4) 

Methanol (CH2OH)

 6668.518 MHz 6661.8 - 6675.2 MHz 3),6) 

Ionized Helium Isotope (3HeII)

 8665.65 MHz 8660.0 - 8670 MHz 

Methanol (CH3OH)

 12.178 GHz 12.17 - 12.19 GHz 3),6) 

Formaldehyde (HCHO)

 14.488 GHz 14.44 - 14.5 GHz 3),4) 

Cyclopropenylidene (C3H2)

 18.343 GHz 18.28 - 18.36 GHz 3),4),6)

Water Vapour (H2O)

 22.235 GHz 22.16 - 22.26 GHz 3),4) 

Ammonia (NH3)

 23.694 GHz 23.61 - 23.71 GHz 4) 

Ammonia (NH3)

 23.723 GHz 23.64 - 23.74 GHz 4) 

Ammonia (NH3)

 23.87 GHz 23.79 - 23.89 GHz 4) 

Silicon monoxide (SiO)

 42.821 GHz 42.77 - 42.86 GHz 

Silicon monoxide (SiO)

 43.122 GHz 43.07 - 43.17 GHz 

Carbon monosulphide (CS)

 48.991 GHz 48.94 - 49.04 GHz 

Deuterated formylium (DCO+)

 72.039 GHz 71.96 - 72.11 GHz 3) 

Silicon monoxide (SiO)

 86.243 GHz 86.16 -  86.33 GHz 

Formylium (H13CO+)

 86.754 GHz 86.66 - 86.84 GHz 

Silicon monoxide (SiO)

 86.847 GHz 86.76 - 86.93 GHz 

Ethynyl radical (C2H)

 87.3 GHz 87.21 - 87.39 GHz 5) 

Hydrogen cyanide (HCN)

 88.632 GHz 88.34 - 88.72 GHz 4) 

Formylium (HCO+)

 89.189 GHz 88.89 - 89.28 GHz 4) 

Hydrogen isocyanide (HNC)

 90.664 GHz 90.57 - 90.76 GHz 

Diazenylium (N2H)

 93.174 GHz 93.07 - 93.27 GHz 

Carbon monosulphide (CS)

 97.981 GHz 97.65 - 98.08 GHz 4) 

Carbon monoxide (C18O)

 109.782 GHz 109.67 - 109.89 GHz 

Carbon monoxide (13CO)

 110.201 GHz 109.83 - 110.31 GHz 4) 

Carbon monoxide (C17O)

 112.359 GHz 112.25 - 112.47 GHz 6) 

Carbon monoxide (CO)

 115.271 GHz 114.88 - 115.39 GHz 4) 

Formaldehyde (HCHO)

 137.45 GHz 137.31 - 137.59 GHz 3),6) 

Formaldehyde (HCHO)

 140.84 GHz 140.69 - 140.98 GHz 

Carbon monosulphide (CS)

 146.969 GHz 146.82 - 147.12 GHz 

Water vapour (H2O)

 183.31 GHz 183.12 - 183.5 GHz 

Carbon monoxide (C18O)

 219.56 GHz 219.34 - 219.78 GHz 

Carbon monoxide (13CO)

 220.399 GHz 219.67 - 220.62 GHz 4) 

Carbon monoxide (CO)

 230.538 GHz 229.77- 230.77 GHz 4) 

Carbon monosulphide (CS)

 244.953 GHz 244.72 - 245.2 GHz 6) 

Hydrogen cyanide (HCN)

 265.886 GHz 265.62 - 266.15 GHz 

Formylium (HCO+)

 267.557 GHz 267.29 - 267.83 GHz 

Hydrogen isocyanide (HNC)

 271.981 GHz 271.71 - 272.25 GHz 

Dyazenulium (N2H+)

 279.511 GHz 279.23 - 279.79 GHz 

Carbon monoxide (C18O)

 312.33 GHz 329.00 - 329.66 GHz 

Carbon monoxide (13CO)

 330.587 GHz 330.25 - 330.92 GHz 

Carbon monosulphide (CS)

 342.883 GHz 342.54 - 343.23 GHz 

Carbon monoxide (CO)

 345.796 GHz 345.45 - 346.14 GHz 

Hydrogen cyanide (HCN)

 354.484 GHz 354.13 - 354.84 GHz 

Formylium (HCO+)

 356.734 GHz 356.37 - 357.09 GHz 

Dyazenulium (N2H+)

 372.672 GHz 372.30 - 373.05 GHz 

Water vapour (H2O)

 380.197 GHz 379.81 - 380.58 GHz 

Carbon monoxide (C18O)

 439.088 GHz 438.64 - 439.53 GHz 

Carbon monoxide (13CO)

 440.765 GHz 440.32 - 441.21 GHz 

Carbon monoxide (CO)

 461.041 GHz 460.57 - 461.51 GHz 

Heavy water (HDO)

 464.925 GHz 464.46 - 465.39 GHz 

Carbon (CI)

 492.162 GHz 491.66 - 492.66 GHz 

Water vapour (H218O)

 547.676 GHz 547.13 - 548.22 GHz 

Water vapour (H2O)

 556.936 GHz 556.37 - 557.5 GHz 

Ammonia (15NH3)

 572.113 GHz 571.54 - 572.69 GHz 

Ammonia (NH3)

 572.498 GHz 571.92 - 573.07 GHz 

Carbon monoxide (CO)

 691.473 GHz 690.78 - 692.17 GHz 

Hydrogen cyanide (HCN)

 797.433 GHz 796.64 - 789.23 GHz 

Formylium (HCO+)

 802.653 GHz 801.85 - 803.85 GHz 

Carbon monoxide (CO)

 806.652 GHz 805.85 - 807.46 GHz 

Carbon (CI)

 809.35 GHz 808.54 - 810.16 GHz 

1): If Note 4) or Note 2) are not listed, the band limits are Doppler-shifted frequencies corresponding to radial velocities of +/- 300 km/s (consistent with line radiation occurring in our galaxy). 
2): An extension to lower frequencies of the allocation of 1400-1427 MHz is required to allow for the Doppler shifts for HI observed in distant galaxies. 
3): The current international allocation is not primary and/or does not meet bandwidth requirements. See: ITU-R Radio Regulations for more detailed information. 
4): Because these line frequencies are also being used for observing other galaxies, the listed bandwidths include Doppler shifts corresponding to radial velocities of up to 1000 km/s. It should be noted that HI has been observed at frequencies redshifted to 500 MHz, while some lines of the most abundant molecules have been detected in galaxies with velocities up to 50000 km/s, corresponding to a frequency reduction of up to 17%.
5): There are six closely spaced lines associated with this molecule at this frequency. The listed band is wide enough to permit observations of all six lines. 
6): This line is not mentioned in Article 8 of the ITU-R Radio Regulations. 

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