Circular polarization of ion fluorescence completing the analysis of resonant Xe* 4d(-1)(5/2)6p Auger decay

The relative contributions of the partial electron waves emitted in the Auger decay of the Xe* 4d(-1)(5/2)6p(J(*)=1) resonance have been determined by fluorescence polarimetry after excitation with circularly polarized synchrotron radiation. The analysis of circularly polarized fluorescence of the photoion leads to an independent determination of the orientation parameters for all states of the Xe II 5p(4)6p multiplet. The present study provides, in combination with data on the angular distribution and spin polarization of the Auger electrons, complete quantum mechanical information on the resonant Auger decay, i.e., branching ratios and relative phases of the Auger decay amplitudes.     

Enhancement of double auger decay probability in xenon clusters irradiated with a soft-x-ray laser pulse

The interaction of large Xe clusters with a soft x-ray laser pulse having a wavelength of 13.9 nm and an intensity of up to 2x10(10) W/cm2 was investigated using a time-of-flight ion mass spectrometer. The corresponding laser photon energy was sufficiently high to photoionize Xe 4d innershell electrons. It was found that Xe3+ ions (which result from double Auger decay of 4d vacancies) became the dominant final ionic product with increasing cluster size and x-ray intensity. This is in contrast to the results of synchrotron radiation experiments involving free Xe atoms, in which Xe2+ is the dominant resultant ion species. Possible mechanisms responsible for the enhancement of the double Auger transition probability in x-ray laser and cluster interaction are discussed.     

Multielectron spectroscopy: the xenon 4d hole double auger decay

A magnetic bottle spectrometer of the type recently developed by Eland et al. [Phys. Rev. Lett. 90, 053003 (2003).] has been implemented for use with synchrotron radiation, allowing multidimensional electron spectroscopy. Its application to the Xe 4d double Auger decay reveals all the energy pathways involved. The dominant path is a cascade process with a rapid (6 fs) ejection of a first Auger electron followed by the slower (>23 fs) emission of a second Auger electron. Weaker processes implying 3 electron processes are also revealed, namely, direct double Auger and associated Rydberg series.     

Double photoionization into double core-hole states in Xe

Double photoionization (DPI) leading to double core-hole states of Xe2+ 4d(-2) has been studied using a magnetic bottle time-of-flight spectrometer. The assignments of the Xe2+ 4d(-2) states are confirmed by the Auger lines extracted from fourfold coincidences including two photoelectrons and two Auger electrons. It is estimated that the core-core DPI into Xe2+ 4d(-2) at a photon energy of 301.6 eV has a favored cross section of about 0.3 MB. The intense core-core DPI is due to mixing of the 4d(-2) continuum with the 4p single photoionization, which is manifested in the relative intensities of the Xe2+ 4d(-2) components.     

Energy and angular distributions of electrons emitted by direct double auger decay

We have observed the direct L(2,3)MMM double Auger transition after photoionization of the 2p shell of argon by angle-resolved electron-electron coincidence spectroscopy. The process is responsible for about 20% of the observed Auger electron intensity. In contrast to the normal Auger lines, the spectra in double Auger decay show a continuous intensity distribution. The energy and angular distributions of the emitted electrons allow one to obtain information on the electron correlations giving rise to the double Auger process as well as the symmetry of the associated two-electron continuum state.     

Photoionization of highly charged ions using an ECR ion source and undulator radiation

Photoionization of Xe4+ to Xe7+ ions was studied by combining an electron cyclotron resonance ion source with synchrotron radiation. Multiconfiguration Dirac-Fock calculations were performed to interpret the data. Many autoionization lines were measured and identified, resulting from excitation of a 4d electron into nf and np orbitals followed by Auger decay of the excited states. Continuum photoionization is negligible for the higher members of the isonuclear series.     

Anisotropic ultrafast dissociation probed by the Doppler effect in resonant photoemission from CF4

The resonant Auger spectrum from the decay of F 1s-excited CF4 is measured. Several lines exhibit a nondispersive kinetic energy as the exciting photon energy is tuned through the resonance region. The F 1s(-1) atomiclike Auger line is split into two components due to the emission of Auger electrons by a fragment in motion, when electron emission is observed along the polarization vector of the light. This Doppler splitting is direct evidence that the core excitation leads to T(d)-->C(3v) symmetry lowering, by elongation of a specific C-F bond preferentially aligned along the polarization vector of the incident photon.     

Multiple photoionization of atoms and small molecules by synchrotron radiation

Absorption of one VUV photon by an atom or a molecule can induce the ejection of several electrons through different processes. Such multiple ionization processes, studied by coincidence electron spectroscopy, provide a wealth of information on electron correlations. A magnetic bottle electron time of flight spectrometer implemented on synchrotron radiation centers has allowed the efficient detection in coincidence of two, three and up to five electrons with good energy resolution. The branching ratios of the different processes are easily extracted from the experimental spectra due to the constant transmission of the spectrometer. Multiple Auger decay was observed in rare gases atoms after inner-shell ionization, while core-valence and core-core initial double ionization followed by Auger decay are other pathways to multiple ionization. For molecules, Coulomb explosion with energy released in ionic fragments may occur after multiple ionization, nevertheless, coincidence electron spectroscopy can also provide a clear interpretation for peculiar decay channels in molecules.     

Unveiling residual molecular binding in triply charged hydrogen bromide

We present an experimental and theoretical study of triply charged hydrogen bromide ions formed by photoionization of the inner 3d shell of Br. The experimental results, obtained by detecting the 3d photoelectron in coincidence with the two subsequent Auger electrons, are analyzed using calculated potential energy curves of HBr3+. The competition between the short-range chemical binding potential and the Coulomb repulsion in the dissociative process is shown. Two different mechanisms are observed for double Auger decay: one, a direct process with simultaneous ejection of two Auger electrons to final HBr3+ ionic states and the other, a cascade process involving double Auger decay characterized by the autoionization of Br*+ ion subsequent to the HBr2+ fragmentation.     

Polarization and dichroism in atomic Auger spectroscopy following absorption of circularly polarized light

Spin resolved Auger current is shown to be different for the absorption of left and right circularly polarized light. This current is produced in non-radiative spontaneous decay of photoexcited atoms or of excited atomic photoions. Circular dichroism in such polarized Auger electrons exists even in the absence of spin-orbit interaction. Physical and geometrical conditions, necessary for the occurrence of dichroic effects in atomic Auger spectroscopy, have been obtained. Calculations for Ba and Xe show that the effect is substantially large and can be readily observed.     

Experimental evidence of interatomic coulombic decay from the auger final states in argon dimers

Interatomic Coulombic decay (ICD) from an Auger-final dicationic state is observed in the Ar dimer. A 2p inner-shell vacancy created by photoionization is replaced with 3s and 3p vacancies via intra-atomic Auger decay. The Auger-final dicationic state is subject to ICD in which one of the 3p electrons in the same Ar atom fills the 3s vacancy while one of the 3p electrons from the neighboring Ar atom is emitted as an ICD electron. This ICD process is unambiguously identified by electron-ion-ion coincidence spectroscopy in which the kinetic energy of the ICD electron and the kinetic energy release between Ar+ and Ar2+ are measured in coincidence.     

Cs Ⅳ离子4d内壳层激发态衰变过程的相对论理论研究

在相对论多组态Dirac-Fock理论方法基础上,通过系统考 虑电子关联效应和由于内壳层电子激发而导致的电子自旋-轨道波函数的弛豫效应,详细研究了Cs Ⅳ离子的4d内壳层电子激发组态4d95s25p5、辐射末态4d105s25p4及Auger末态4d105s25p3和4d105s15p4的能级结构及各种可能的辐射和Auger衰变过程.获得了与已有的实验结果和相关的半经 验准相对论组态相互作用计算结果相符的辐射跃迁能、振子强度以及线宽,预言了4d95s25p5态的以Auger衰变为主的 Auger电子谱的特 关键词： 内壳层激发态 辐射衰变 Auger衰变     

Multiple Auger Decay Following Xe~+(4p_(3/2)~(-1)) Ionization

The Auger decay for the many-electron Xe~+(4p_(3/2)~(-1)) state is studied in detail,using multistep approaches.It is found that the single Auger decay channels are primarily Coster-Kronig processes,which is in accord with other theoretical and experimental results.The double and triple Auger decays result primarily from cascade processes,i.e.,the sequential two-step and three-step Auger decay,and as such,the contributions from direct processes can be neglected.Level-to-level rates for single,double,and triple decays are obtained,based on which comprehensive Auger electron spectra and ion yields are obtained.Our decay paths and Auger electron spectra are in agreement with the experimental analysis [Hikosaka et al.,Phys.Rev.A 76(2007) 032708],and our ion yield ratios(Xe~(2+):Xe~(3+):Xe~(4+)=4.6:87.0:8.4) are also in line with their values(5.0:86.0:9.0).However,with respect to the ion yield ratios,a discrepancy still remains among the experimental and theoretical results.Taking into account the complexity of Xe's electronic structure,further,more detailed experiments are still required.     

Decay of cystalline order and equilibration during the solid-to-plasma transition induced by 20-fs microfocused 92-eV free-electron-laser pulses

We have studied a solid-to-plasma transition by irradiating Al foils with the FLASH free electron laser at intensities up to 10(16) W/cm(2). Intense XUV self-emission shows spectral features that are consistent with emission from regions of high density, which go beyond single inner-shell photoionization of solids. Characteristic features of intrashell transitions allowed us to identify Auger heating of the electrons in the conduction band occurring immediately after the absorption of the XUV laser energy as the dominant mechanism. A simple model of a multicharge state inverse Auger effect is proposed to explain the target emission when the conduction band at solid density becomes more atomiclike as energy is transferred from the electrons to the ions. This allows one to determine, independent of plasma simulations, the electron temperature and density just after the decay of crystalline order and to characterize the early time evolution.     

Multiple Auger Decay Following Xe+(4p3−1/2)Ionization

The Auger decay for the many-electron Xe+(4p3^?1/2)state is studied in detail,using multistep approaches.It is found that the single Auger decay channels are primarily Coster–Kronig processes,which is in accord with other theoretical and experimental results.The double and triple Auger decays result primarily from cascade processes,i.e.,the sequential two-step and three-step Auger decay,and as such,the contributions from direct processes can be neglected.Level-to-level rates for single,double,and triple decays are obtained,based on which comprehensive Auger electron spectra and ion yields are obtained.Our decay paths and Auger electron spectra are in agreement with the experimental analysis[Hikosaka et al.,Phys.Rev.A 76(2007)032708],and our ion yield ratios(Xe²⁺:Xe³⁺:Xe⁴⁺=4.6:87.0:8.4)are also in line with their values(5.0:86.0:9.0).However,with respect to the ion yield ratios,a discrepancy still remains among the experimental and theoretical results.Taking into account the complexity of Xe’s electronic structure,further,more detailed experiments are still required.     

Primary chemical reactions induced by radioactive nuclear transformations

A series of chemical reactions is suggested to describe primary chemical transformations induced by Auger electrons from radioactive nuclear decay in glassy and crystalline frozen aqueous media. The mechanism is based on Mössbauer emission spectroscopy data supplemented by data on reactions in the tracks of fast positrons and electrons in an aqueous medium. It is shown that variation of temperature, the degree of crystallinity, the concentration of electron acceptors, etc., results in correlated changes in the yields of the final reaction products—Fe²⁺, Fe³⁺ or Sn²⁺, Sn⁴⁺ ions, positronium atoms, and molecular radiolytic hydrogen. These correlations indicate the similarity of chemical processes in the nanometer vicinity of decayed ⁵⁷Co and ^119mSn nuclei and in the tracks of fast positrons and electrons. This similarity is caused by the same behavior of secondary intratrack electrons produced due to ionization losses of fast positrons, electrons, and Auger electrons.     

Xe(4d~(10))(e,2e)反应三重微分截面的理论研究

采用修正后的扭曲波玻恩近似理论,计算了共面不对称几何条件下Xe(4d~(10))(e,2e)反应的三重微分截面.散射电子能量为1000 eV,敲出电子能量为20 eV,散射电子角度分别固定在2°,4°和7.5°.理论计算与Avaldi等人的实验结果和扭曲波玻恩近似理论计算进行了比较,发现出射电子之间的后碰撞相互作用较弱,极化效应在反应过程中起着重要作用.     

Double Auger decay of A 3d vacancy in Krypton

All possible channels of double Auger decay of a 3d vacancy in a Kr atom are investigated using perturbation theory in a basis of Hartree-Fock wave functions. The energy spectrum of the Auger electrons and the total decay width are calculated. The role of model decay mechanisms is discussed, along with the importance of taking correlation interactions into account. Tomsk Polytechnic University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 54–63, October, 1998.     

Very fast hollow-atom decay processes in Xe30+-C60 collisions

In Xe30+-C60 collisions at low velocity (0.2 a.u.相似文献   

Auger electron spectroscopy studies of CO on Ni spectral line shapes and quantitative aspects

The true secondary electron peak of aluminium is observed during the cleaning process controlled by Auger spectroscopy. The features which appear are studied in relation with the electron energy loss spectrum. This observation confirms the hypothesis of emission of secondary electrons by the plasmon decay.