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