Inner-shell vacancies, excited atom states

When the nuclear charge changes due to radioactive decay and/or an inner-shell vacancy is produced, the bound electrons in the same atom or molecule experience the sudden change in the central potential and have a small but finite probability to be excited to an unoccupied bound state (shakeup) or ejected to the continuum (shakeoff). We calculated the shakeup-plu.s-shakeoff probabilities accompanying PI and EC using the method of Carlson and Nestor [45]. 

The potential of the SW approach to systematize inneratomic properties and processes can be easily illustrated by reconsidering chemically induced nuclear lifetime variations which, among others, are of relevance to the calibration problem of Moessbauer isomer shifts. Highly excited atom states carrying single or multiple vacancies in inner shells form another promising subject of SW simulations. In the latter case the results of a DV-Xa study of the K-shell x-ray satellite intensities of metal fluorides can be used for a comparative assessment of both methods. 

Creation and decay of highly excited atom states carrying inner-shell vacancies... 

The Auger electrons and characteristic X-rays are emitted from initial states with one inner-shell vacancy or sometimes with several vacancies in inner-and outer-shells, where the initial states are formed by ionization and excitation of inner- and outer-shell electrons. In ionization of the isolated atom, constituents of all the atomic orbitals except for an ionized electron remain unchanged after... 

With AES, the sample is subjected to a high-energy (typically 2-20 KeV) electron beam that can cause ejection of a core electron from an atom to form an atomic inner shell vacancy. An outer-level electron will then fill the inner-level vacancy, which will induce an excited state. One of the ways that the atom can then relax is by emitting another electron to form a doubly ionized species. This electron is the Auger electron (named for Pierre Auger, who recognized the effect... 

In order to see in what range of atomic number Z the collapse of the 3d-orbital occurs for different inner-shell vacancy states we calculate the mixing coefficient b2 of the configuration 3d2(ls) into wave functions (6). The coefficients b are plotted against atomic number Z in Fig. 16. From this figure it can be seen that the collapse occurs in a rather small range of AZ and for a vacancy it occurs just for Z = 20, i.e. the Ca atom. From this we conclude that the unexpected strong excitation of excited 2p-vacancy states in Ca can be considered as an... 

The second step is the stabilization of the ionized atom. It corresponds to the re-emission of all, or part, of the energy acquired during excitation. Almost instantaneous (in 10 s), an electron from an outer orbit of the atom jumps in to occupy the vacancy. Since outer shell electrons are more energetic than inner shell electrons, the relocated electron has an excess of energy that is expended as an X-ray fluorescence photon. In this way, the atom returns to its ground state very quickly. 

The principle of both of these techniques is to excite the atoms of the substance to be analyzed by bombarding the sample with sufficiently energetic X-rays/y-rays or charged particles. The ionization (photoionization for XRF and ionization caused due to Coulomb-interaction in case of PIXE) of inner-shell electrons is produced by the photons and charged particles, respectively. When this interaction removes an electron from a specimen s atom, frequently an electron from an outer shell (or orbital) occupies the vacancy. The distribution of electrons in the ionized atom is then out of equilibrium and within an extremely short time s) returns to the normal state, by transitions... 

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