Average atomic weight: 39.948(1) u
| Isotope | Fraction | Atomic weight/u |
| 36 | 0.003336(21) | 35.967545105(28) |
| 38 | 0.000629(7) | 37.96273211(21) |
| 40 | 0.996035(25) | 39.9623831237(24) |
Atomic weights and isotopic compositions were obtained from NIST Database 144
Ar I (Ar-like): 449 levels, 26251 lines (E1: 23658 IC: 2590 M1: 1 E2: 1 M2: 1), transition probabilities for 428 lines
Ar II (Cl-like): 334 levels, 9452 lines (E1: 6738 IC: 2712 M1: 1 E2: 1), transition probabilities for 2145 lines
Ar III (S -like): 125 levels, 1890 lines (E1: 859 IC: 1019 M1: 5 E2: 7), transition probabilities for 1442 lines
Ar IV (P -like): 70 levels, 819 lines (E1: 386 IC: 415 M1: 9 E2: 9), transition probabilities for 719 lines
Ar V (Si-like): 25 levels, 79 lines (E1: 39 IC: 28 M1: 5 E2: 7), transition probabilities for 79 lines
Ar VI (Al-like): 43 levels, 332 lines (E1: 178 IC: 146 M1: 3 E2: 4 M2: 1), transition probabilities for 294 lines
Ar VII (Mg-like): 60 levels, 485 lines (E1: 291 IC: 189 M1: 2 E2: 2 M2: 1), transition probabilities for 377 lines
Ar VIII (Na-like): 61 levels, 486 lines (E1: 486), transition probabilities for 486 lines
Ar IX (Ne-like): 97 levels, 1270 lines (E1: 687 IC: 579 M1: 2 E2: 1 M2: 1), transition probabilities for 753 lines
Ar X (F -like): 67 levels, 725 lines (E1: 354 IC: 369 M1: 1 E2: 1), transition probabilities for 654 lines
Ar XI (O -like): 21 levels, 64 lines (E1: 31 IC: 21 M1: 5 E2: 7), transition probabilities for 61 lines
Ar XII (N -like): 28 levels, 113 lines (E1: 48 IC: 46 M1: 9 E2: 10), transition probabilities for 107 lines
Ar XIII (C -like): 25 levels, 116 lines (E1: 58 IC: 46 M1: 5 E2: 7), transition probabilities for 116 lines
Ar XIV (B -like): 15 levels, 35 lines (E1: 28 IC: 1 M1: 3 E2: 3), transition probabilities for 35 lines
Ar XV (Be-like): 10 levels, 21 lines (E1: 9 IC: 7 M1: 2 E2: 2 M2: 1), transition probabilities for 21 lines
Ar XVI (Li-like): 29 levels, 158 lines (E1: 108 IC: 50), transition probabilities for 62 lines
Ar XVII (He-like): 44 levels, 314 lines (E1: 193 IC: 121), transition probabilities for 123 lines
Ar XVIII (H -like): 225 levels, 3086 lines (E1: 3086), transition probabilities for 3086 lines
(Atomic Line List v3.00b5)
