A study of and satellite states observed by `threshold photoelectrons coincidence' spectroscopy

Abstract

The Ar 2+ and Ne 2+ spectra have been studied from their respective thresholds up to their respective triple ionization potentials by threshold photoelectrons coincidence (TPEsCO) spectroscopy. The np 4 , nsnp 5 and ns 0 np 6 (n = 2, 3 in Ne and Ar, respectively) states of the dications as well as the np 3 n l satellite states, where two electrons are ejected and one is promoted into an unfilled orbital, have been observed. This study is the first extensive observation of the satellite states of dications by electron emission spectroscopy and extends the previous observations by optical emission spectroscopy to the region of the triple ionization threshold. New features have been discerned in the spectra and an assignment is proposed based on previous results from optical spectroscopy and on calculations with an atomic multiconfigurational Dirac-Fock code.

Strong configuration interaction in the double ionization spectra of noble gases studied by the relativistic propagator method

“…4). By using the threshold photoelectrons coincidence (TPEsCO) method, Avaldi et al [9] could resolve for the first time the 2s 2 2p 4 ( 3 P 2,1,0 ) multiplet of Ne 2+ with spacings of 80 and 35 meV. The corresponding calculated splittings amount to 80.3 and 37.8 meV and thus are in very good agreement to the experimental values.…”

“…However, this spectrum differs dramatically from the experimental spectrum (see, for example, Refs. [9,13]), which shows the pronounced intensity decrease when going from outer-valence to inner-valence spectral regions. The intensity of the 2s 0 2p 6 ( 1 S 0 ) state is particularly weak.…”

“…Except for some anomalies in the intensity distributions [8,9,13,15], the main states in the low-energy spectral regions of these ions describing the removal of the two outermost p electrons are well understood, which makes this class of dications excellent candidates for testing and calibration of new methods. The situation is more complex in deeper energy regions, where at least one of the emitted electrons belongs to the outermost s shell.…”

Experimental observation of initial-state effects in photo-double-ionization of Ne2s

“…The symmetries of both the residual ion and electron pair in the final state, 1 S e and 1 P o , respectively, as well as the kinetic energy of the ejected electrons are the same. The double-ionization potential of the Ne 2+ ͑2s −2 2p 6 ͒ state, 121.9 eV [21][22][23], is lower than the binding energy of the 4 S ground state of the Ne 3+ ion [23]. Thus decay to the triple continuum is not allowed.…”

Complete double valence photoionization study of the electron spectra of krypton

“…So far, neon has been thoroughly explored and the cross section for the formation of states related to the 2s 1 2p 5 and 2s 0 2p 6 configurations has been determined by both optical spectroscopy [5] and electron-electron coincidence spectroscopy [6]. Threshold photoelectron coincidence (TPEsCO) [7] studies have been carried out for photon energies covering the entire region below the core levels in neon and argon [8], as well as in xenon [9].…”