Ground state of the carbon atom in strong magnetic fields

The ground and a few excited states of the carbon atom in external uniform magnetic fields are calculated by means of our two-dimensional mesh Hartree-Fock method for field strengths ranging from zero up to 2.35 x 10(9) T. With increasing field strength the ground state undergoes six transitions involving seven different electronic configurations which belong to three groups with different spin projections S-z=-1,-2,-3. For weak fields the ground-state configuration arises from the field-free 1s(2)s(2)2p(0)2p(-1), S-z = -1 configuration. With increasing field strength the ground state involves the four S-z = -2 configurations 1 s(2)s(2)2p(0)2p(-1)2p(+1), 1s(2)s2p(0)2p(-1)3d(-2). 1s(2)2p(0)2p(-1)3d(-2)4f(-3), and 1s(2)2p(-1)3d(-2)4f(-3)5g(-4), followed by the two fully spin-polarized S-z=-3 configurations 1s2p(0)2p(-1)3d(-2)4f(-3)5g(-4) and 1s2p(-1)3d(-2)4f(-3)5g(-4),6h(-5). The last configuration forms the ground state of the carbon atom in the high-field regime gamma>18.664. The above series of ground-state configurations is extracted from the results of numerical calculations for more than 20 electronic configurations selected due to some general energetic arguments. [S1050-2947(99)05310-4].