Final state selection in the 4p photoemission of Rb by combining laser spectroscopy with soft-x-ray photoionization

Fine structure resolved 4p photoemission studies have been performed on free rubidium atoms in the ground state and after excitation into the [Kr]5p ²P_1∕2 and ²P_3∕2 states. The 4p⁵5p final states have been excited in the 4p⁶5s→4p⁵5p conjugate shakeup process from ground state atoms as well as by direct photoemission from laser excited atoms. The relative intensities differ considerably in these three excitation schemes. The differences in the laser excited spectra could be described well using calculations based on the pure jK-coupling scheme. Thereby it was possible to specify the character of the various final states. Furthermore it has been possible to resolve two of the final states whose energy separation is smaller than the experimental resolution by selectively exciting them in a two step scheme, where the laser selects the spin-orbit coupling in the intermediate state and determines the final state coupling after x-ray photoemission.