Interstellar Molecules Frank J. Lovas and Lewis E. Snyder A number of molecules have been detected in the interstellar References medium, in circumstellar envelopes around evolved stars, and co- mae and tails of comets through observation of their microwave, 1 . Lovas, F . J ., Recommended Rest Frequencies for Observed Interstellar infrared, or optical spectra . The following list gives the molecules Molecule Microwave Transitions — 2002 Revision, J. Phys. Chem. Ref. and the particular isotopic species that have been reported so far . Data 33, 177–355 (2004); and update appearing at http://physics .nist . gov/PhysRefData/micro/html/contents .html Molecules are listed by molecular formula in the Hill order . All 2 . Snyder, L . E ., Cometary Molecules, Internat . Astron . Union species not footnoted otherwise are observed in interstellar clouds, Symposium No . 150, Astrochemistry of Cosmic Phenomena, ed . P . D . while some are also found in comets and circumstellar clouds . The Singh, Kluwer Academic Publishers, Dordrecht, The Netherlands, pp . list was last updated in October 2008 and lists 162 molecules (298 427–434 (1992) . isotopic forms) .
Molecular Molecular formula Name Isotopic species formula Name Isotopic species AlCl Aluminum monochloride Al35Cla HCOOD Al37Cla DCOOH a AlF Aluminum monofluoride AlF CH2S Thioformaldehyde H2CS a 13 CAlN Aluminum isocyanide AlNC H2 CS + + 34 CF Fluoromethylidynium ion CF H2C S CH Methylidyne CH HDCS + + CH Methyliumylidene CH D2CS a CHN Hydrogen cyanide HCN CH3 Methyl CH3 13 H CN CH3N Methanimine CH2NH 15 13 HC N CH2NH
DCN CH3NO Formamide NH2CHO 13 CHN Hydrogen isocyanide HNC NH2 CHO 15 + + H NC CH3O Hydroxymethylium ion H2COH 13 HN C CH4 Methane CH4
DNC CH4O Methanol CH3OH 15 13 D NC CH3OH 18 CHNO Isocyanic acid HNCO CH3 OH
DNCO CH2DOH
CHNO Hydroxyl cyanide HOCN CH3OD
CHNS Isothiocyanic acid HNCS CHD2OH
CHO Oxomethyl HCO CD3OH + + CHO Oxomethylium HCO CH4S Methanethiol CH3SH 13 + H CO CH5N Methylamine CH3NH2 HC17O+ CMgN Magnesium cyanide MgCNa HC18O+ CMgN Magnesium isocyanide 24MgNCa DCO+ 25MgNCa D13CO+ 26MgNCa CHO+ Hydroxymethylidyne HOC+ CN Cyanide radical CN + + 13 CHO2 Hydroxyoxomethylium HOCO CN CHP Phosphaethyne HCPa C15N CHS+ Thiooxomethylium HCS+ CN+ Cyanide radical ion CN+ b a CH2 Methylene CH2 CNNa Sodium cyanide NaCN + + a CH2N Iminomethylium HCNH CNSi Silicon cyanide SiCN a CH2N Methylene amidogen CH2N CNSi Silicon isocyanide SiNC b CH2N2 Cyanamide NH2CN CN2 Cyanoimidogen NCN
CH2O Formaldehyde H2CO CO Carbon monoxide CO 13 13 H2 CO CO 18 17 H2C O C O HDCO C18O 13 17 D2CO C O 13 18 CH2O2 Formic acid HCOOH C O H13COOH 14CO
14-7 14-8 Interstellar Molecules
Molecular Molecular formula Name Isotopic species formula Name Isotopic species + + CO Carbon monoxide ion CO C3 Tricarbon C3
COS Carbon oxysulfide OCS C3H Cyclopropenylidyne c-C3H OC34S c-CC13CH 13 O CS C3H Propenylidyne l-C3H 18 OCS C3HN Cyanoacetylene HCCCN 13 CO2 Carbon dioxide CO2 H CCCN + + b 13 CO2 Carbon dioxide ion CO2 HC CCN CP Carbon phosphide CPa HCC13CN CS Carbon monosulfide CS HCCC15N C33S DCCCN 34 C S C3HN Isocyanoacetylene HCCNC 36 C S C3HN 3-Imino-1,2-propadienylidene HNCCC 13 CS C3H2 Cyclopropenylidene c-C3H2 13C34S c-H13CCCH CSi Silicon carbide SiCa c-HC13CCH
C2 Dicarbon C2 c-C3HD
C2H Ethynyl C2H C3H2 Propadienylidene l-H2CCC 13 + + CCH C3H2N Protonated cyanoacetylene HCCCNH 13 C CH C3H2O 2-Propynal HCCCHO
C2D C3H2O Cyclopropenone c-C3H2O
C2HN Cyanomethylene HCCN C3H3N Acrylonitrile (vinyl cyanide) CH2CHCN 13 C2HNO Cyanoformaldehyde CNCHO CH2CHCN 13 C2H2 Acetylene HCCH CH2 CHCN
C2H2N Cyanomethyl CH2CN C3H4 Propyne CH3CCH 13 C2H2O Ketene H2CCO CH3C CH 13 C2H3N Acetonitrile CH3CN CH3CCH 13 CH3CN CH2DCCH 13 CH3 CN CH3CCD 15 CH3C N C3H4O Propenal CH2CHCHO
CH2DCN C3H5N Propanenitrile (ethyl cyanide) CH3CH2CN 13 C2H3N Isocyanomethane CH3NC CH3CH2CN 13 C2H3N Keteneimine CH2CNH CH3 CH2CN 13 C2H4 Ethylene H2CCH2 CH3CH2 CN
C2H4N2 Aminoacetonitrile NH2CH2CN C3H6 Propylene CH2CHCH3
C2H4O Acetaldehyde CH3CHO C3H6O Acetone (CH3)2CO
C2H4O Ethylene oxide c-C2H4O C3H6O Propanal CH3CH2CHO
C2H4O anti-Ethenol a-CH2CHOH C3N Cyanoethynyl CCCN 13 C2H4O syn-Ethenol s-CH2CHOH CCCN 13 C2H4O2 Methyl formate CH3OCHO C CCN 13 C2H4O2 Acetic acid CH3COOH CC CN - - C2H4O2 Glycolaldehyde CH2OHCHO C3N Cyanoethynyl anion CCCN
C2H5NO Acetamide CH3CONH2 C3O 1,2-Propadienylidene, 3-oxo CCCO b C2H6 Ethane CH3CH3 C3S 1,2-Propadienylidene, 3-thioxo CCCS 34 C2H6O trans-Ethanol t-CH3CH2OH CCC S 13 C2H6O gauche-Ethanol g-CH3CH2OH C CCS
C2H6O Dimethyl ether CH3OCH3 C3Si Silicon tricarbon SiC3
C2H6O2 Ethylene glycol HOCH2CH2OH C4H 1,3-Butadiynyl radical HCCCC 13 C2O Oxoethenylidene CCO H CCCC a 13 C2P Phosphaethenylidene CCP HC CCC 13 C2S Thioxoethenylidene CCS HCC CC CC34S HCCC13C 13CCS DCCCC 13 - - C CS C4H 1,3-Butadiynyl anion HCCCC
C2Si Silicon dicarbide c-SiC2 C4HN 3-Cyano-1,2-propadienylidene HCCCCN 29 c- SiC2 C4H2 Butatrienylidene H2CCCC 30 a c- SiC2 C4H2 1,3-Butadiyne HCCCCH 13 c-Si CC C4H3N 2-Butynenitrile CH3CCCN Interstellar Molecules 14-9
Molecular Molecular formula Name Isotopic species formula Name Isotopic species
C4H3N Cyanoallene CH2CCHCN H2O Water H2O a 18 C4Si Silicon tetracarbide SiC4 H2 O SiCCC13C HDO a C5 Pentacarbon C5 D2O + + b C5H 2,4-Pentadiynylidyne HCCCCC H2O Oxoniumyl H2O
C5HN 2,4-Pentadiynenitrile HCCCCCN H2S Hydrogen sulfide H2S 13 34 H CCCCCN H2 S HC13CCCCN HDS 13 HCC CCCN D2S 13 + + HCCC CCN H3 Trihydrogen ion H3 13 + HCCCC CN H2D + DCCCCCN D2H
C5H4 1,3-Pentadiyne CH3C4H H3N Ammonia NH3 15 C5N 1,3-Butadiynylium, 4-cyano C5N NH3
C6H 1,3,5-Hexatriynyl HCCCCCC NH2D - - C6H 1,3,5-Hexatriynyl anion HCCCCCC NHD2 a C6H2 1,3,5-Hexatriyne HCCCCCCH ND3 + + C6H2 1,2,3,4,5-Hexapentaenylidene H2CCCCCC H3O Oxonium hydride H3O a C6H3N Methylcyanodiacetylene CH3C4CN H4Si Silane SiH4
C6H6 Benzene C6H6 NO Nitric oxide NO
C7H 2,4,6-Heptatriynylidyne HCCCCCCC NP Phosphorous nitride PN
C7HN 2,4,6-Heptatriynenitrile HC7N NS Nitrogen sulfide NS 34 C7H4 Methyltriacetylene CH3C6H N S
C8H 1,3,5,7-Octatetraynyl HC8 NSi Silicon nitride SiN - - C8H 1,3,5,7-Octatetraynyl anion HC8 N2 Nitrogen N2 + + b C9HN 2,4,6,8-Nonatetraynenitrile HC9N N2 Nitrogen ion N2
C11HN 2,4,6,8,10-Undecapentaynenitrile HC11N N2O Nitrous oxide N2O ClH Hydrogen chloride H35Cl OP Phosphorus monoxide POa H37Cl OS Sulfur monoxide SO ClK Potassium chloride K35Cla 34SO K37Cla 33SO ClNa Sodium chloride Na35Cla S18O Na37Cla OS+ Sulfur monoxide ion SO+ FH Hydrogen fluoride HF OSi Silicon monoxide SiO FeO Iron monoxide FeO Si18O HLi Lithium hydride 7LiH 29SiO HN Imidogen HN 30SiO
HNO Nitrosyl hydride HNO O2 Oxygen O2 + + HN2 Hydrodinitrogen(1+) N2H O2S Sulfur dioxide SO2 15 + 33 NNH SO2 15 + 34 N NH SO2 + 17 N2D OS O HO Hydroxyl OH OS18O 17OH SSi Silicon monosulfide SiS 18OH Si33S HO+ Oxoniumylidene OH+ b Si34S HS Mercapto SH 29SiS 29 34 H2 Hydrogen H2 Si S 30 H2N Amidogen NH2 SiS 30Si34S b S2 Sulfur S2 l- before the isotopic species indicates a linear configuration, while c- indicates a cyclic molecule . a Reported only in circumstellar clouds . b Reported only in comets .