STRONG ALIGNMENT OBSERVED FOR THE TIME-REVERSED PHOTOIONIZATION PROCESS STUDIED IN RELATIVISTIC COLLISIONS WITH BARE URANIUM IONS

In high-energy atomic collisions between bare high-Z projectiles and l ow-Z target atoms, an electron may be captured radiatively into an exc ited projectile state which subsequently decays by x-ray emission. Thi s process is the inverse of two-photon-one-electron ionization, in whi ch the first photon resonantly excites an electron from the hydrogenic 1s(1/2) ground state and a second photon ionizes the excited electron . We present an experimental and theoretical study of the angular dist ribution of the Ly-alpha(1) (2p(3/2) --> 1s(1/2)) x rays following rad iative electron capture. From the observed anisotropic emission patter n a significant alignment of the intermediate 2p(3/2) state is deduced .