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RGA Spectra AMU Guide

AMU # Chemical Symbol Sources
1 H Water F or hydrogen F
2 H2, D Hydrogen, deuterium (2H)
3 HD, 3H Hydrogen-deuterium, tritium (3H)
4 He Helium
5 No known elements
6 C DI 12C (rare)
7 N DI 14N (rare)
8 O DI 16O (rare)
9 No known elements
10 Ne, 10B DI 20Ne (rare), BF3, BCl3
11 Ne, 11B DI 22Ne (rare), 11BF3, 11BCl3
12 C Carbon, carbon monoxide F, carbon dioxide F
13 C, 13C Methane F, carbon isotope
14 N, CH2 Nitrogen, methane F or Note 1
15 CH3 Methane F or Note 1
16 O, CH4, NH2 Oxygen, carbon monoxide F, ammonia
17 OH, NH3 Water F, ammonia F
18 H2O Water
19 F Fluorine, freon F
20 Ar2+, Ne, HF DI argon, neon, hydrofluoric acid
21 No known elements
22 22Ne, CO2 Neon, DI CO2
23 No known elements
24 C2 See Note 1
25 C2H See Note 1
26 C2H2, CN See Note 1, hydrogen cyanide F
27 C2H3, Al, HCN See Note 1, aluminum, hydrogen cyanide
28 N2, CO, C2H4, Si Nitrogen, carbon monoxide, ethylene P, silicon
29 CH3CH2 Ethane F, ethanol F, isopropyl alcohol
30 C2H6, NO Ethane P, nitric oxide
31 P, CH2O Oxygen, methanol F
32 O2, S Oxygen, sulfur, methanol P
33 HS Hydrogen sulfide F
34 H2S, 34S, O2 Hydrogen sulfide P, sulfur isotope, oxygen isotope
35 Cl Chlorine isotope, See Note 2
36 HCl, 36Ar, C3 Hydrochloric acid, argon isotope, hydrocarbons
37 37Cl, C3H Chlorine isotope, See Note 2, hydrocarbons
38 37HCl, C3H2 Hydrochloric acid, See Note 2, hydrocarbons
39 C3H3 See Note 3, hydrocarbons
40 Ar, C3H4 Argon, See Note 1, hydrocarbons
41 C3H5 See Note 1, hydrocarbons
42 C3H6 See Note 1, hydrocarbons
43 C3H7, CH3CO See Note 1, acetone F, methyl ethyl ketone F
44 CO2, C3H8 Carbon dioxide, See Note 3
45 CH3CH2O Ethanol F, isopropyl alcohol F
46 CH3CH2OH Ethanol P
47 C35Cl See Note 2
48 HC35Cl, SO See Note 2, sulfur dioxide F
49 C37Cl See Note 2
50 C37Cl, CF2, C4H2 See Note 2, freon F, See Note 3


  1. Fragments of several hydrocarbons, such as mechanical pump oil, diffusion pump oil, vacuum grease, cutting oil, or organic solvents.
  2. Fragments of several chlorinated ydrocarbons, such s carbon tetrachloride, trichloroethylene, and many freons.
  3. Fragments from both straight chained hydrocarbons and benzene ring hydrocarbons.
  4. F = Fragment Ion, P = Parent Ion, DI = Doubly Ionized
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