Table VII. Electronic-structure contributions to the 2 p$_{1}$$_{/}$$_{2}$ − 2 s and 2 p$_{3}$$_{/}$$_{2}$ − 2 s transition energies in Li-like ions, in eV. The nuclear-charge rms radii 〈 r $^{2}$〉1 / 2 (in fm) are taken from Refs. [16, 56]. The uncertainty given is due to the higher-order interelectronic interaction only. The first one is caused by the numerical procedure while the second one is due to the Breit approximation. a Reference [55]. b Reference [48]. 20 Z 〈 r $^{2}$〉1 / 2 Transition Dirac 1ph 2ph ⩾ 3ph Total Total Ref. [13] 3 2.431 2 p$_{1}$$_{/}$$_{2}$ − 2 s 0.00000 5.77750 -3.28214 -0.6484 1.8470(20)(0) 1.8466(105) 1 . 84812 a 1 . 8486 b 3 2.431 2 p$_{3}$$_{/}$$_{2}$ − 2 s 0.00367 5.76900 -3.27566 -0.6499 1.8471(20)(0) 1.8466(105) 1 . 84816 a 1 . 8486 b 5 2.406 2 p$_{1}$$_{/}$$_{2}$ − 2 s 0.00000 9.64178 -3.29242 -0.3522 5.9972(15)(0) 5.9963(32) 5 . 9986(3) b 5 2.406 2 p$_{3}$$_{/}$$_{2}$ − 2 s 0.02832 9.60222 -3.27437 -0.3548 6.0014(15)(0) 6.0004(32) 6 . 0027(3) b 7 2.558 2 p$_{1}$$_{/}$$_{2}$ − 2 s -0.00001 13.52503 -3.30788 -0.2354 9.9817(10)(0) 9.9814(21) 9 . 9823(3) b 7 2.558 2 p$_{3}$$_{/}$$_{2}$ − 2 s 0.10889 13.41639 -3.27242 -0.2391 10.0138(10)(0) 10.0133(21) 10 . 0144(3) b 10 3.005 2 p$_{1}$$_{/}$$_{2}$ − 2 s -0.00008 19.40227 -3.34105 -0.1545 15.9067(6)(0) 15.9064(10) 15 . 9068(3) b 10 3.005 2 p$_{3}$$_{/}$$_{2}$ − 2 s 0.45426 19.08472 -3.26835 -0.1598 16.1108(6)(0) 16.1105(10) 16 . 1111(3) b 15 3.189 2 p$_{1}$$_{/}$$_{2}$ − 2 s -0.00046 29.40265 -3.42321 -0.0942 25.8848(3)(0) 25.8851(5) 25 . 8848(3) b 15 3.189 2 p$_{3}$$_{/}$$_{2}$ − 2 s 2.30928 28.32447 -3.25801 -0.1025 27.2732(3)(0) 27.2734(5) 27 . 2735(3) b