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

A magnetic bottle time-of-flight spectrometer has been used to perform spectroscopy of K n⁺ and Rb n⁺ 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(³P)3d ¹ ⁴D energy levels of K²⁺ are assigned.