Table I. Individual contributions to the mass shift coefficient K (GHz · amu) for the 2 p$_{1}$$_{/}$$_{2}$ − 2 s and 2 p$_{3}$$_{/}$$_{2}$ − 2 s transitions in lithium (Z=3). ∗ The experimental values include also terms of higher orders in m/M . like systems. Most accurate results for lithium are presently obtained utilizing variational solutions of the three-body Schr¨ odinger problem and accounting for the relativistic and QED corrections within the αZ expansion [43, 44]. We use these results to estimate the residual correlation effects in our calculations. Analyzing the convergence of the calculated atomic properties as a function of the configuration basis set, the difference between the results obtained by two alternative methods described above, and the deviation of our nonrelativistic 7 Subset 2 p$_{1}$$_{/}$$_{2}$ − 2 s 2 p$_{3}$$_{/}$$_{2}$ − 2 s Ref. MS operator -443.81(20) -443.82(20) -443.86 nr -443.86 nr -2534.48 hyd -2535.12 hyd NMS -245.48 -245.49 SMS -198.78 -198.77 -198.73 nr -198.73 nr -198.920(2) nr -198.920(2) nr [39–41] -198.8 nr -198.8 nr [42] RNMS 0.33 0.38 RSMS 0.12 0.06 QED -0.08(3) -0.08(3) 1-el QED -0.08 -0.08 2-el QED 0.00 0.00 Total theory -443.9(2) -443.9(2) -444.086 -444.103 [43, 44] -447(12) -447(12) [35] Experiment ∗ -444.09(3) [45] -444.04(4) -444.06(4) [46]