Abstract
The excitation of (3p)54s and (3p)54p levels of Ar is investigated by use of the Born approximation and a four-state calculation including 1S0(3p)6, 1S0(3p)54p and P1(3p)54s (M=0,1). HF-type wavefunctions are used. The spin-orbit coupling is treated in a rather semiempirical way.