Average atomic weight: 35.446–35.457 u
| Isotope | Fraction | Atomic weight/u |
| 35 | 0.7576(10) | 34.968852682(37) |
| 37 | 0.2424(10) | 36.965902602(55) |
Atomic weights and isotopic compositions were obtained from NIST Database 144
Cl I (Cl-like): 430 levels, 17351 lines (E1: 14743 IC: 2603 M1: 3 E2: 1 M2: 1), transition probabilities for 284 lines
Cl II (S -like): 274 levels, 9037 lines (E1: 3576 IC: 5449 M1: 5 E2: 7), transition probabilities for 922 lines
Cl III (P -like): 78 levels, 931 lines (E1: 405 IC: 507 M1: 9 E2: 10), transition probabilities for 619 lines
Cl IV (Si-like): 44 levels, 290 lines (E1: 203 IC: 75 M1: 5 E2: 7), transition probabilities for 171 lines
Cl V (Al-like): 32 levels, 93 lines (E1: 84 IC: 2 M1: 3 E2: 4), transition probabilities for 73 lines
Cl VI (Mg-like): 46 levels, 175 lines (E1: 161 IC: 10 M1: 2 E2: 2), transition probabilities for 128 lines
Cl VII (Na-like): 46 levels, 177 lines (E1: 177), transition probabilities for 177 lines
Cl VIII (Ne-like): 28 levels, 35 lines (E1: 34 IC: 1), transition probabilities for 5 lines
Cl IX (F -like): 54 levels, 457 lines (E1: 226 IC: 229 M1: 1 E2: 1), transition probabilities for 457 lines
Cl X (O -like): 58 levels, 91 lines (E1: 70 IC: 16 M1: 2 E2: 3), transition probabilities for 88 lines
Cl XI (N -like): 47 levels, 128 lines (E1: 105 IC: 12 M1: 5 E2: 6), transition probabilities for 128 lines
Cl XII (C -like): 33 levels, 90 lines (E1: 62 IC: 23 M1: 2 E2: 3), transition probabilities for 85 lines
Cl XIII (B -like): 30 levels, 105 lines (E1: 97 IC: 4 M1: 3 E2: 1), transition probabilities for 3 lines
Cl XIV (Be-like): 53 levels, 353 lines (E1: 349 M1: 2 E2: 2), transition probabilities for 46 lines
Cl XV (Li-like): 47 levels, 409 lines (E1: 335 IC: 74), transition probabilities for 124 lines
Cl XVI (He-like): 29 levels, 136 lines (E1: 85 IC: 51), transition probabilities for 80 lines
Cl XVII (H -like): 225 levels, 3076 lines (E1: 3076), transition probabilities for 3076 lines
(Atomic Line List v3.00b5)
