Internal spin-orbit coupling and electron exchange in the excitation of np(5)(n+1)p states of neon, krypton and xenon atoms by polarized electrons

Excitation of np(5)(n + 1)p states by polarized electrons has been studied for target atoms of neon, krypton and xenon. The integrated state multipole s have been determined from the measurement of the integrated Stokes parame ters of the corresponding decay photons from the excited states of np(5)(n + 1)p [5/2](3), np(5) (n + 1)p' [3/2](2) and np(5)(n + 1)p' [3/2](1) (n = 3 , 5 and 6 for Ne, ICI and Xe, respectively) within 2.5 eV of threshold. It is found that the combined effects of electron exchange with the internal s pin-orbit interaction play a significant role in the excitations of the abo ve J = 2 and 1 states. Negative angular momentum transfer is observed in th e excitation of these J = 2 and 1 stares of Kr and Xe atoms, and it is attr ibuted to internal spin-orbit interactions. Pure electron exchange is the m echanism for the excitation of all the J = 3 LS-coupled states, since they show no experimental evidence of spin-orbit interaction. Although the gener al behaviour of the deduced state multipoles is in agreement with predictio ns from semi-relativistic R-matrix (close-coupling) calculations, there rem ain differences of detail that are most notable for the T(J)(20) multipole of the J = 1 states of all of these atoms.