Post-collision interaction after inner-shell ionization by electron impact: the shape of Auger lines

The energy shift of lines arising from the decay of the (np5(n + 1)s2)2P3/2 autoionizing states in Na (n = 2) and Cs (n = 5) atoms has been studied for the first time in ejected-electron spectra measured over the excess energy range −0.1 to 5.4 eV. In Na spectra, the energy dependence of the shift possesses a clear oscillatory-like character. In particular, the shift becomes of negative or positive sign depending on the presence or absence of a negative-ion resonance structure in the excitation function of the (2p53s2)2P3/2 state. Earlier, we reported a similar behaviour of the line shift for the (3p54s2)2P3/2 autoionizing state in K atoms. Though in Cs atoms the strong negative-ion resonance is also present close to the excitation threshold of the (5p56s2)2P3/2 state, in contrast to Na and K data, the energy dependence of the line shift possesses a smooth asymptotic behaviour described well by the classical model of the post-collision effect. The comparative analysis of the spectroscopic classification of the resonance structure in the excitation of the (np5(n + 1)s2)2P3/2 autoionizing states in Na, K and Cs atoms has shown that the observed effect most probably reflects the complication of the compound character of resonances. In whole, the obtained data show that under the condition of the high polarizability of a resonantly excited target the relation between polarization attraction, centrifugal and Coulomb repulsion becomes a crucial factor which determines the final energy distribution of outgoing electrons.

“…These predictions were confirmed by numerous experimental investigations performed mainly with gaseous atoms and ions (e.g. see [7] and references therein).…”

Section: Introductionsupporting

confidence: 62%

The post-collision energy shift of the (np⁵(n+ 1)s²)²P_3/2lines in autoionizing spectra of sodium (n= 2) and caesium (n= 5) atoms excited by electron impact

Borovik¹,

Ogurtsov²

2010

“…[2,3] and references therein) predict similar line shift behaviour, which was confirmed also by numerous experimental investigations (e.g. see [4] and references therein). Note, however, that all of these works dealt mainly with the targets possessing small or moderate polarizability (noble gases or some simple molecules [5]) and for which the resonance excitation plays a minor role as compared to the total excitation efficiency of autoionizing states [6].…”

Section: Introductionsupporting

confidence: 82%

The post-collision interaction effect in autoionizing spectra of alkali atoms excited by electron impact

Borovik¹,

Roman²,

Ogurtsov³

2013

Ejected-electron energy spectra resulting from decay of the (4p55s2)2P3/2, 1/2 autoionizing states in rubidium atoms have been studied at electron impact energies up to 5 eV above the excitation thresholds. The energy shift of corresponding lines due to the post-collision interaction (PCI) involving the outgoing electrons and the residual ion have been observed for the first time. For both states the energy dependence of the shift possesses a smooth asymptotic behaviour which is satisfactorily described by the classical model of the PCI effect. Similar behaviour of the line shift was reported earlier also for the (5p56s2)2P3/2 autoionizing state in heavier Cs atoms. Both results contrast with the clear oscillatory-like character of the line shift for the (np5[n + 1]s2)2P3/2, 1/2 autoionizing states in the lighter Na (n = 2) and K (n = 3) atoms. The comparative analysis of the data on the PCI effect and excitation cross-sections of the (np5[n + 1]s2)2P3/2, 1/2 autoionizing states in Na (n = 2), K (n = 3), Rb (n = 4) and Cs (n = 5) atoms has shown that the high polarizability of the resonantly excited target and partial structure of resonances are the main factors which determine the dynamics of the PCI shift of lines in ejected-electron spectra of alkali atoms.

“…This effect manifests itself in the fact that the lines in the ejected-electron spectrum are shifted, broadened and take non-Gaussian shapes. To date numerous experimental investigations of the PCI in different collision processes have been performed mainly with gaseous atoms and ions (e.g., see [3] and references therein).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of post-collision interaction in the near-threshold electron excitation of the (3p⁵4s²)²P_3/2,1/2autoionizing states in potassium

Borovik

Ogurtsov

2009

The post-collision interaction (PCI) energy shift of lines corresponding to the decay of the (3p54s2)2P3/2,1/2 lowest autoionizing states in potassium atoms was studied by precisely measuring the ejected-electron spectra in the excess energy range between 0 and 3.5 eV. The energy dependence of the line shift for both states reveals a complicated character. In particular, instead of the smooth asymptotic behaviour predicted by available models of PCI, the shift can possess both positive and negative sign in an excess energy region between 0.2 and 1.3 eV. Comparison of these data with the near-threshold excitation cross sections of the (3p54s2)2P3/2,1/2 states showed that such behaviour is observed in the same energy regions where the negative-ion resonance structure is present in excitation functions. To explain the observed features, the effect of core-polarization on the final energy distribution of outgoing electrons is considered and the possibility of the negative line shift for the and states is shown by numerical evaluation.