Multielectron spectroscopy: energy levels of K n+ and Rb n+ ions (n = 2, 3, 4)

A magnetic bottle time-of-flight spectrometer has been used to perform spectroscopy of Kn+ and Rbn+ states with ionization degrees n of 2, 3 and 4. Energy levels are directly measured by detecting in coincidence the n electrons that are emitted as a result of single photon absorption. Experimental results are compared with the energies from the NIST atomic database and ab initio multiconfiguration Dirac-Fock calculations. Previously unidentified 3p(4)(P-3)3d(1) D-4 energy levels of K2+ are assigned.