Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition (2015)

Chapter: Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz

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Suggested Citation: "Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz." National Academies of Sciences, Engineering, and Medicine. 2015. Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/21774.
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C

International Astronomical Union Spectral Lines of Most Importance Below 300 GHz

At each triennial meeting of the General Assembly, the International Astronomical Union (IAU) reviews carefully the list of astrophysically most important spectral lines that it maintains. The IAU expresses the need to protect these frequency bands from in-band, band-edge, and harmonic emissions, especially from spaceborne transmitters.

In preparation for World Radiocommunication Conference 2000, which revised the allocations above 71 GHz, a millimeter-wavelength working group of the Scientific Committee on Frequency Allocations for Radio Astronomy and Space Science (IUCAF) examined all then-known transitions in the millimeter and submillimeter wavebands. The working group selected a limited number of the astrophysically most important spectral lines to supplement the earlier lists, such as those produced by the IAU, to be used in allocating frequency bands to the Radio Astronomy Service. Spectral lines below 300 GHz are listed in Table C.1. Unless otherwise noted, the suggested minimum band limits are Doppler-shifted frequencies corresponding to radial velocities of ±300 km/s, consistent with line radiation occurring in our Milky Way galaxy. Spectral lines with primary (P), secondary (S), or footnote (F) protection status are noted in Table C.1.

Page 238 Cite
Suggested Citation: "Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz." National Academies of Sciences, Engineering, and Medicine. 2015. Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/21774.
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TABLE C.1 The Most Important Spectral Lines Below 300 GHz

Species Formula Frequency (GHz) Suggested Minimum Band (GHz) Band Allocation Status Notes (1)
Deuterium Di 0.327384 0.327-0.3277 P  
Hydrogen Hi 1.420406 1.370-1.427 S 1.33-1.40 2, 3
P 1.40-1.427
Hydroxyl radical OH 1.612231 1.6068-1.6138 P 1.6106-1.6138 4
1.665402 1.6598-1.6671 P 1.66-1.67 4
1.667359 1.6618-1.6690   4
Hydroxyl radical OH 1.720530 1.7148-1.7222 S 1.7188-1.7222 3, 4
Methyladyne CH 3.263794 3.2424-3.2671 S 3.260-3.267 3, 4
3.335481 3.3244-3.3388 S 3.332-3.339 3, 4
3.349193 3.3380-3.3525 S 3.3458-3.3525 3, 4
Formaldehyde H2CO 4.829660 4.8136-4.8345 S 4.8-4.9 3, 4
Methanol CH3OH 6.668518 6.6618-6.6752 S 6.650-6.6752 3
Helium 3He+ 8.665650 8.6570-8.6743   3, 6
Methanol CH3OH 12.178 12.17-12.19   3, 6
Formaldehyde H2CO 14.488 14.44-14.50 S 14.47-14.50 3, 4
Cyclopropenylidene C3H2 18.343 18.28-18.36   3, 4, 6
Water vapor H2O 22.235 22.16-22.26 F 22.01-22.21 3, 4
      P 22.21-22.50  
Ammonia NH3 23.694 23.61-23.71 P 23.60-24.00 4
23.723 23.64-23.74   4
23.870 23.79-23.89   4
Sulphur monoxide SO 30.002 29.97-30.03   6
Methanol CH3OH 36.169 36.13-36.21 P 36-37 6
Silicon monoxide SiO 42.519 42.47-42.57 F 42.77-42.87 6, 8
42.821 42.78-42.86 F 43.07-43.17  
43.122 43.08-43.17 F 43.37-43.47  
43.424 43.38-43.47    
Dicarbon monosulphide CCS 45.379 45.33-45.42   6
Carbon monosulphide CS 48.991 48.94-49.04 P 48.94-49.04  
Oxygen O2 61.1 56.21-63.06 P 58.2-59.0 5, 6, 7
Deuterated water HDO 80.578 80.50-80.66    
Cyclopropenylidene C3H2 85.339 85.05-85.42    
Silicon monoxide SiO 86.243 86.16-86.33 P  
Formylium H13CO+ 86.754 86.67-86.84 P  
Silicon monoxide SiO 86.847 86.76-86.93 P  
Ethynyl radical C2H 87.300 87.21-87.39 P 5
Hydrogen cyanide HCN 88.632 88.34-88.72 P 4
Formylium HCO++ 89.189 88.89-89.28 P 4
Hydrogen isocyanide HNC 90.664 90.57-90.75 P  
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Suggested Citation: "Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz." National Academies of Sciences, Engineering, and Medicine. 2015. Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/21774.
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Species Formula Frequency (GHz) Suggested Minimum Band (GHz) Band Allocation Status Notes (1)
Diazenylium N2H+ 93.174 93.08-93.27    
Carbon monosulphide CS 97.981 97.65-98.08   4
Sulfur monoxide SO 99.300 99.20-99.40    
Methyl acetylene CH3CCH 102.5 102.39-102.60   5
Methanol CH3OH 107.014 106.91-107.12    
Carbon monoxide C18O 109.782 109.67-109.89 P  
Carbon monoxide 13CO 110.201 110.83-110.31 P 4
Carbon monoxide C17O 112.359 112.25-112.47 P 6
Cyano radical CN 113.500 113.39-113.61 P 5
Carbon monoxide CO 115.271 114.88-115.39 P 4
Oxygen O2 118.750 118.63-118.87 P 116-126 7
Formaldehyde H213CO 137.450 137.31-137.59   6
Formaldehyde H2CO 140.840 140.69-140.98 P  
Carbon monosulphide CS 146.969 146.48-147.12 P 146.82-147.12  
Nitric oxide NO 150.4 149.95-150.85 S 150-151 5
Methanol CH3OH 156.602 156.45-156.76    
Water vapor H2O 183.310 183.13-183.49    
Carbon monoxide C18O 219.560 219.34-219.78 P  
Carbon monoxide 13CO 220.399 219.67-220.62 P 4
Cyano radical CN 226.600 226.37-226.83 P 5
Cyano radical CN 226.800 226.57-227.03 P 5
Carbon monoxide CO 230.538 229.77-230.77 P 4
Carbon monosulphide CS 244.953 244.14-245.20   6
Nitric oxide NO 250.6 250.35-250.85 P 5
Ethynyl radical C2H 262.000 261.74-262.26   5
Hydrogen cyanide HCN 265.886 265.00-266.15    
Formylium HCO++ 267.557 266.66-267.82    
Hydrogen isocyanide HNC 271.981 271.71-272.25    
Diazenylium N2H+ 279.511 279.23-279.79    
Carbon monosulphide CS 293.912 292.93-294.21    

NOTES:

1. If Notes 2 or 4 are not listed, then the band limits are the Doppler-shifted frequencies corresponding to radial velocities of ± 300 km/s (consistent with line radiation occurring in our Milky Way galaxy).

2. An extension to lower frequency of the allocation of 1 400-1 427 MHz is required to allow for the higher Doppler shifts for HI observed in distant galaxies.

3. The current international allocation is not primary and/or does not meet bandwidth requirements. See the Radio Regulations (RR) for more detailed information.

Page 240 Cite
Suggested Citation: "Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz." National Academies of Sciences, Engineering, and Medicine. 2015. Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/21774.
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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 1,000 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 50,000 km/s, corresponding to a frequency reduction of up to 17%.

5. There are several closely spaced lines associated with these molecules. The listed bands are wide enough to permit observations of all lines.

6. This line frequency is not mentioned in RR Article 5.

7. These lines are observable only outside the atmosphere.

8. A portion of the “suggested minimum band” for this line extends outside the band allocated to the radio astronomy service. Protection for observations conducted in this portion of the band may not be practicable.

SOURCE: Data and further information can be found in the International Telecommunication Union, RA 314 Series: Preferred Frequency Bands for Radio Astronomical Measurements, June 2003, http://www.itu.int/dms_pubrec/itu-r/rec/ra/R-REC-RA.314-10-200306-I!!PDF-E.pdf.

Page 237 Cite
Suggested Citation: "Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz." National Academies of Sciences, Engineering, and Medicine. 2015. Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/21774.
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Page 238 Cite
Suggested Citation: "Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz." National Academies of Sciences, Engineering, and Medicine. 2015. Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/21774.
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Page 239 Cite
Suggested Citation: "Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz." National Academies of Sciences, Engineering, and Medicine. 2015. Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/21774.
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Page 240 Cite
Suggested Citation: "Appendix C: International Astronomical Union Spectral Lines of Most Importance Below 300 GHz." National Academies of Sciences, Engineering, and Medicine. 2015. Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/21774.
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Page 240
Next Chapter: Appendix D: International Astronomical Union Spectral Lines of Most Importance Between 300 and 1000 GHz
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