Z-dependences in the reorganization of inner-shell ionized atoms

Mohammedein, Adel M.; Reiche, Ina; Zschornack, G.

doi:10.1080/10420159308219732

Cited by 5 publications

(7 citation statements)

References 14 publications

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“…Data for noble gases show that shake-up and shake-off effects were of comparable magnitude (Svensson et al, 1988;Armen et al, 1985;Wark et al, 1991). Calculations on carbon, oxygen and nitrogen by Mohammedein et al, 1993 andEl-shemi &Hassan, 1997 show that photoemission accompanied by double Auger decay has nearly zero probability for these light elements. Such triple ionisations can thus be neglected in the ionisation dynamics of C, O, N compounds.…”

Section: Discussionmentioning

confidence: 97%

“…Sulfur, on the other hand, behaves differently, and the probability of multiple ionization (n > 2) after the ejection of a K‐shell photoelectron is larger. The average charge left in sulfur after a single K‐shell photoionization is estimated to be ∼4 (Mohammedein et al 1993). For instance, for S: P(2) ∼5%, P(4) ∼34%, P(6) ∼3% (Mohammedein et al 1993; El‐Shemi and Hassan 1997).…”

Section: Discussionmentioning

confidence: 99%

“…The average charge left in sulfur after a single K‐shell photoionization is estimated to be ∼4 (Mohammedein et al 1993). For instance, for S: P(2) ∼5%, P(4) ∼34%, P(6) ∼3% (Mohammedein et al 1993; El‐Shemi and Hassan 1997). This implies that for sulfur, multiple ionization mechanisms should be taken into consideration to obtain more accurate predictions for the ionization dynamics of proteins.…”

Section: Discussionmentioning

confidence: 99%

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Shake‐up and shake‐off excitations with associated electron losses in X‐ray studies of proteins

et al. 2001

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Photoionization of an atom by X-rays usually removes an inner shell electron from the atom, leaving behind a perturbed "hollow ion" whose relaxation may take different routes. In light elements, emission of an Auger electron is common. However, the energy and the total number of electrons released from the atom may be modulated by shake-up and shake-off effects. When the inner shell electron leaves, the outer shell electrons may find themselves in a state that is not an eigen-state of the atom in its surroundings. The resulting collective excitation is called shake-up. If this process also involves the release of low energy electrons from the outer shell, then the process is called shake-off. It is not clear how significant shake-up and shake-off contributions are to the overall ionization of biological materials like proteins. In particular, the interaction between the outgoing electron and the remaining system depends on the chemical environment of the atom, which can be studied by quantum chemical methods. Here we present calculations on model compounds to represent the most common chemical environments in proteins. The results show that the shake-up and shake-off processes affect ∼20% of all emissions from nitrogen, 30% from carbon, 40% from oxygen, and 23% from sulfur. Triple and higher ionizations are rare for carbon, nitrogen, and oxygen, but are frequent for sulfur. The findings are relevant to the design of biological experiments at emerging X-ray free-electron lasers.Keywords: X-rays; photoionization; shake-up; shake-off; Auger emission; radiation damage; peptides; proteins Computer simulations show that ultrashort and high-intensity X-ray pulses, as those expected from presently developed free-electron lasers (Winick 1995;Wiik 1997), may provide structural information from large protein molecules and assemblies before radiation damage destroys them. Estimation of radiation damage as a function of X-ray photon energy, pulse length, integrated pulse intensity, and sample size was obtained in the framework of a radiation damage model, where the effects of atom-photon and ion-ion interaction were taken into account. Photons of 1 Å wavelength, corresponding to a photon energy of ∼12 keV, interact with atoms mainly through the photoelectric effect (Dyson 1973) (for carbon the photoelectric crosssection is ∼10 times higher than the corresponding elastic cross-section at this wavelength; Hubbel et al. 1980), and thus the photoelectric effect is the main source of radiation damage with X-rays.Photoionization may proceed either through the ejection of an outer shell electron or through the ejection of an inner shell electron (Dyson 1973). Outer shell photo-events eject a single electron from the atom with an energy equivalent to the energy of the incoming photon minus the shell-binding

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Shake‐up and shake‐off excitations with associated electron losses in X‐ray studies of proteins

et al. 2001

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“…There have been extensive studies using the Monte Carlo procedure for decay pathways of an inner-shell vacancy produced by x-ray synchrotron or electron capture [32][33][34][35][36][37][38][39][40][41][42][43][44]. In particular, the inner-shell decay process for heavy atoms such as iodine and xenon [34,[36][37][38] has brought much interest because of their relevance for medical applications [38,45].…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo calculation of ion, electron, and photon spectra of xenon atoms in x-ray free-electron laser pulses

Son

Santra

2012

Phys. Rev. A

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When atoms and molecules are irradiated by an x-ray free-electron laser (XFEL), they are highly ionized via a sequence of one-photon ionization and relaxation processes. To describe the ionization dynamics during XFEL pulses, a rate equation model has been employed. Even though this model is straightforward for the case of light atoms, it generates a huge number of coupled rate equations for heavy atoms like xenon, which are not trivial to solve directly. Here, we employ the Monte Carlo method to address this problem and we investigate ionization dynamics of xenon atoms induced by XFEL pulses at a photon energy of 4500 eV. Charge state distributions, photo-/Auger electron spectra, and fluorescence spectra are presented for x-ray fluences of up to 10 13 photons/µm 2 . With the photon energy of 4500 eV, xenon atoms can be ionized up to +44 through multiphoton absorption characterized by sequential one-photon single-electron interactions.

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“…Up to now, a number of Monte Carlo simulations have been done on vacancy cascades in various rare gases and some other elements, in particular by Mukoyama [16], Mirakhmedov and Parilis [17], Opendak [18], Krause et al [19][20][21], Mohammedein et al [22] and Kochur et al [23,24].…”

Section: Introductionmentioning

confidence: 99%

Ion charge state distributions as a result of reorganization effects in inner-shell ionized atoms

El-Shemi

Lofty

Zschornack

1997

J. Phys. B: At. Mol. Opt. Phys.

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Ion charge state distributions due to vacancy cascades following K-, L 1 -, L 2 -and L 3 -shell ionization are calculated using a Monte Carlo technique. Probabilities P (q) that the de-excited ions become q-fold ionized after a single primary ionization are given as a function of the atomic number in the region Z = 10-60. The calculations are accomplished by tracing successive radiative and non-radiative transitions and electron shake-off as an additional effect. Thereby, radiative and non-radiative transition rates and shake-off probabilities have been calculated from relativistic wavefunctions.

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Z-dependences in the reorganization of inner-shell ionized atoms

Cited by 5 publications

References 14 publications

Shake‐up and shake‐off excitations with associated electron losses in X‐ray studies of proteins

Shake‐up and shake‐off excitations with associated electron losses in X‐ray studies of proteins

Monte Carlo calculation of ion, electron, and photon spectra of xenon atoms in x-ray free-electron laser pulses

Ion charge state distributions as a result of reorganization effects in inner-shell ionized atoms

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