Excitation and decay dynamics of 1s2s inner-shell double-vacancy states of neon atoms

The photo-excitation and Auger decay processes of inner-shell double vacancy states 1s2s2p^6（1,3^S）3s3p of neutral neon atoms have been studied theoretically. Multi-configuration Dirac-Fock （MCDF） calculations have been carried out, with electron correlation effects taken into consideration. The relaxation of core and excited orbitals and configuration interaction are found to be crucial to creating the double vacancy states by single photo-absorption. The predominant decay paths for the double vacancy states turn out to be of the LLM Auger decay to 1s 2s^22p^53s（3p）, KLL Auger decay to 1s^22s2p^43s3p, and KLM Auger decay to 1s^22p^63s（3p）. They lead to further Auger decay, creating the neon ions of multiple charge states. For both double and single vacancy states the spectator type of Auger process is dominated in all the Auger decay processes. Theoretical Anger electron spectra are presented for further investigations, experimental and theoretical.     

Photoemission studies of core exciton decay in KI

The decay of K⁺ 3p-core excitons in KI was studied by using new methods for obtaining photoemission spectroscopy data with synchrotron radiation. The Auger and non-radiative direct-recombination decay processes are separately identified in the data and a measure for the Auger energy distribution is obtained.     

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.     

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.     

Stress dependent kinetics of electron-hole drops in uniaxially deformed silicon

The decay of electron-hole drops in silicon is studied as a function of uniaxial stress applied along the <111 > and <100 > crystallographic directions. For <111 > stress, the decay kinetics can be explained in terms of Auger recombination. In contrast, for <100 > stress, the experimental decay is consistent with a model of free exciton evaporation from droplets rather than Auger recombination.     

Energies, Auger and radiative probabilities of the doubly-excited 1s23l3l′ states for Be-like neon

Energy levels, Auger decay and radiative transition rates of the doubly-excited 1s ²3l3l′ states for Be-like neon are calculated using relativistic Multiconfiguration Dirac-Fock (MCDF) method. Electron correlation and relaxation effects are taken into account. The magnitude of Auger rates for the 35 doubly-excited states and their decay channels are discussed. Present calculated values are in agreement with the latest experimental electron spectra as well as other theoretical results.     

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.     

核衰变产生的X射线和俄歇电子数据计算

核衰变过程中,内转换电子发射和电子俘获能在原子电子壳层内留下空穴.其他原子电子壳层的电子将填补这些空穴,其原子电子位置将重排,并发射X射线和俄歇电子.X射线和俄歇电子的能量由原子电子结合能计算得到,X射线和俄歇电子的强度分别由内转换电子发射和电子俘获在原子电子壳层内留下的空穴数,X射线荧光产额,和空穴转移系数计算得到.本文简要介绍核衰变产生的X射线和俄歇电子数据的计算方法、计算程序与工作流程,并以核衰变为例说明其具体应用和简要讨论与总结.     

Laser-enabled Auger decay in rare-gas atoms

In rare-gas atoms, Auger decay in which an inner-valence shell ns hole is filled is not energetically allowed. However, in the presence of a strong laser field, a new laser-enabled Auger decay channel can open up to increase the double-ionization yield. This process is efficient at high laser intensities, where an ns hole can be filled within a few femtoseconds of its creation. This novel laser-enabled Auger decay process is of fundamental importance for controlling electron dynamics in atoms, molecules, and materials.     

Time-resolved Auger decay in CsBr using high harmonics

The temperature-dependent decay dynamics of innershell holes in CsBr was measured by using high harmonics. The measured lifetime was as short as 1.5 ps at 340 K due to increasing the Auger-allowed final state density in the Urbach exciton tail, whereas it is 1.1 ns at 10 K, determined by radiative recombination. The temperature-dependent Auger lifetime extrapolated to a high temperature corresponds to the fully energy-allowed Auger decay. In the model to be presented, this yields an interatomic Auger decay lifetime of 2.4+3.8/-1.5 fs, in line with a theoretical calculation for NaF.     

Dynamics and post-collision interaction effects in two electron decay from the Xenon 4d hole

Two Auger electrons, one very slow, one fast, have been detected in coincidence following near threshold 4d photoionization of the Xe atom. The distribution in the energy the two electrons share has been measured for the first time revealing the presence of post-collision interaction effects that provide unique information on the decay dynamics of the 4d hole. Analysis of the distorted line shapes indicates that the dominant process is decay of Xe+(4d(-1)) to Xe3+ through cascade emission of a zero kinetic energy Auger electron followed by a fast Auger electron. The widths of the intermediate Xe2+* states are estimated to be about 60 meV.     

高双激发Intershell共振态的辐射和Auger跃迁率

采用Conventional infiguration(简写为CI)方法计算了类氦Ar¹⁶⁺离子高双激发Intershell(n>N)共振态的辐射和Auger跃迁率,并利用超球坐标方法和新量子数_n(K,T)_N^A2s+1L^π来作系统分析。计算结果表明,对A=+1态,Auger过程是主要的,辐射过程仅仅是对给定的多重簇(manifold)中更高的态才有意义。对A=0,-1态,Auger宽度更小。对这些 关键词：     

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.     

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.     

Autoionization of triply excited rydberg series

The Auger rates of triply excited Rydberg series are shown to behave rather differently from doubly excited series. It is shown that in hollow atoms the Auger decay rates for Rydberg series of the type 2l2l(')nl(") with n>/=2 are expected to be nearly independent of n, while for doubly excited series of the type 2lnl(') the decay rate in general decreases with increasing n. In addition the ratio between the rates for 2l2l(')nl(") Rydberg series with different l(") values will be fixed and often the ratio will be equal to one.     

Auger transitions initiated from singly and doubly ionized states in Li metal

Major events in Auger spectra from Li surfaces containing both Na and K have been identified. Li Auger transitions initiated from both singly and doubly ionized K shells of Li have been observed. However, no higher energy satellite corresponding to the coupling of the energy of a plasmon decay with that of the Li K VV Auger electrons was detected.     

Quantum coherence in the time-resolved Auger measurement

We present a quantum mechanical model of the attosecond-XUV (extreme ultraviolet) pump and laser probe measurement of an Auger decay [Drescher et al., Nature (London) 419, 803 (2002)]] and investigate effects of quantum coherence. The time-dependent Schr?dinger equation is solved by numerical integration and in analytic form. We explain the transition from a quasiclassical energy shift of the spectrum to the formation of sidebands and the enhancement of high- and low-energy tails of the Auger spectrum due to quantum coherence between photoionization and Auger decay.     

Insulating properties of ultrathin KF layers on Cu(1 0 0): Resonant Auger spectroscopy

Solid-state effects in the creation and decay of K 2p core excitations in thin KF films on Cu(1 0 0) surface have been studied in resonant Auger spectra, excited using synchrotron radiation. The spectra of films of various thickness starting from a single monolayer were measured.The photoabsorption spectra reveal crystal field splitting already at film thickness of about 1 monolayer. The Auger decay spectra of the K 2p⁻¹3d core excitations in films of thickness up to 2 monolayers exhibit a band characteristic of the decay of core ionised states, showing that the excited electron delocalises into substrate before the core hole decays. In thicker films the coexistence of the decay of excited states in the bulk of the KF crystalline film and of ionised states at the KF-metal interface is observed, indicating that the charge transfer probability from the upper layers of the film into the metallic substrate is strongly reduced.     

Interlayer-exciton mediated three-hole-Auger-decay in the π⁎-band of highly oriented pyrolytic graphite

Resonant photoemission spectroscopy (resPES) is used to probe the occupied π- and unoccupied π^⁎-bands of carbon thin films with particular focus on the Auger decay. Highly Oriented Pyrolytic Graphite (HOPG) is studied at the C1s edge. We find strong resonant features at 285.5 eV and 292 eV in the resPES diagram. The normal two-hole Auger decay proceeds under constant kinetic energy (45°) only in the σ^⁎-region. In the π^⁎-region, however, it proceeds under 67.5° in terms of a E_bind(ħω) diagram. We attribute this to a multiple Auger decay with a net three hole final state. For this novel decay process we propose a model. We discuss the long lifetime of the first resonant excitation and conclude that it arises from the strong excitonic character of the first resonant state. We use HOPG as a reference system and suggest that this novel process is a tool to identify interlayer–substrate interaction of the carbon layers involved.     

Stability of ionically bonded surfaces in ionizing environments

We present criteria for the stability of ionic materials in ionizing environments, confining ourselves to cases where the core hole Auger decay mechanism of Knotek and Feibelman is applicable. The main result is that Auger induced decomposition will not occur unless the cation species in the solid is ionized down to a relatively deep filled shell. This shell must be sufficiently deep that an Auger decay starting from it will release the energy necessary for decomposition. The degree to which covalency in bonding affects stability is discussed. We show how these concepts can be applied by examination of the periodic table and a table of electron binding energies.