Table 2. Other species observed in comet, circumstellar, and interstallar sources at IR and UV wavelengths, but not included in Table 4.

Empirical Formula	Name	Isotopic Species	Spectral Region	CA Number	Reference
Interstellar and Circumstellar Species
CH3	Methyl	CH3	IR	[2229-07-7]	Feu00
CH4	Methane	CH4	IR	[74-82-8]	Lac91
CO2	Carbon dioxide	CO2	IR	[124-38-9]	Jus96
C2	Carbon molecule	C2	UV	[12070-15-4]	Cha80
C2H2	Ethyne (acetylene)	HCCH	IR	[74-86-2]	Lac89
C2H4	Ethylene	H2CCH2	IR	[74-85-11]	Cer01a
C2H6	Ethane	CH3CH3	IR	[74-84-0]	Wea99
C4H2	1,3-Butadiyne	HCCCCH	IR	[460-12-8]	Cer01a
C5	Pentacarbon molecule	C5	IR	[12595-82-3]	Ber89
C6H2	1,3,5-Hexatriyne	HCCCCCCH	IR	[3161-99-7]	Cer01a
C6H6	Benzene	C6H6	IR	[71-43-2]	Cer01
HN	Imidogen	HN	UV	[13774-92-0]	Mey91, Swi41
HS	Mercapto (thiohydroxyl)	SH	IR	[13940-21-1]	Yam00
H2	Hydrogen	H2	UV	[1333-74-0]	Car70
H4Si	Silane	SiH4	IR	[7803-62-5]	Kea93
Species Observed Only in Comets.
CN+	Cyanogen ion	CN+	UV	[12539-57-0]	Val92
CN2	Cyano imidogen	NCN	UV	[1884-64-6]	Val92
CO2+	Carbon dioxide ion	CO2+	UV	[12181-61-2]	Swi50
HO+	Oxoniumylidene	OH+	UV	[12259-29-9]	Val92
H2O+	Oxoniumyl	H2O+	UV	[56583-62-1]	Weh74
N2+	Nitrogen ion	N2+	UV	[13966-04-6]	Lut93
S2	Sulfur	S2	UV	[23550-45-0]	A'H83

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