Electron impact excitation of highly charged sodium-like ions

Oscillator strengths, transition probabilities and collision strengths for transitions between n = 3 and n = 4 levels in Ca(X), Fe(XVI), Zn(XX), Kr(XXVI) and Mo(XXXII) have been calculated in a non-relativistic approximation. Wave functions of excited states have been obtained using a semi-empirical procedure. Collision strengths for electron-impact excitation have been calculated in a distorted wave approximation without exchange.Relative intensities of certain emission lines in the sodium isoelectronic sequence are density dependent. An example of this dependence is discussed in the text.     

Interference effects in alignment and orientation processes of atoms excited by polarized radiation

The dynamics of the processes of alignment and orientation of atoms subjected to the action of polarized radiation has been studied theoretically in the energy range of excitation of autoionization resonances. The alignment parameters A ₂₀ for the 4p ⁴5p states of Kr II populated through the excitation and autoionization decay of Kr I 3d ⁹ np resonances depend on energy due to the interference between different resonance channels and the channel of direct photoionization. It is predicted that the orientation parameter O ₁₀ of some Kr II 4p ⁴5p states and the parameter of the angular distribution of photoelectrons β_e1 strongly depend on energy. The absolute photoionization cross sections are calculated for the population of the Kr II 4p ⁴5p states in the case where the energy of excitation photons corresponds to the first four 3d ⁹ np resonances. A good agreement between the calculated and measured photoionization cross sections proves that it is important to take into account the interference between different resonance channels in order to appreciate the dynamics of the Auger decay of Kr I 3d ⁹ np resonances.     

Spectra of rubidium-like Pd X-Sn XIV ions

Palladium, silver, and cadmium spectra excited in a low-inductive vacuum spark have been recorded on a vacuum grazing-incidence spectrograph with a grating of 3600 lines/mm and 3 m in radius, in the range 120–350 Å. The 4p ⁶4d-(4p ⁶5p + 4p ⁶4f + 4p ⁵4d ²) transitions in rubidium-like Pd X-Cd XII spectra have been investigated. Twenty two new spectral lines have been identified from the Dirac-Fock and Hartree-Fock calculations and the known lines were measured with high accuracy. The fine-structure intervals for the 4p ⁶4d ² D ground state and the energies of six, seven, and ten energy levels of excited configurations in Pd X, Ag XI, and Cd XII, respectively, were determined. On the basis of the analysis of isoelectronic regularities in the position of the energy levels, the previous identifications for the In XIII and Sn XIV spectra were refined.     

Beam-foil lifetimes of highly ionized silicon

Electronically excited states of Si ions are created by passing a 20 MeV Si⁵⁺ beam through a thin carbon foil. The EUV-radiation (λ=13–61 nm) emitted by the beam is analyzed using a grazing-incidence spectrometer. From the decay curves, lifetimes of 24 low lying levels in Si VIII to Si XII and of the 4f and 5g levels of Si XI and Si XII are derived. Cascades from doubly excited states turn out to be an important contribution to the radiation observed. The lifetime values of this work are compared to theoretical data mainly of Wiese, Sinanoλu and Dankwort/Trefftz. Most experimental values agree with at least one of the theoretical values. The decay time 560 ps of the 2s2p ^{3 3} D ₃ ⁰ state of Si IX is clearly longer than the theoretical prediction (highest value 455 ps by Sinanoglu).     

Autoionizing and highly excited states in the spectrum of triply ionized tin Sn IV

Transitions from autoionizing states in the spectrum of Sn IV in the range 200–630 Å, occurring due to the excitation of electrons from the inner 4d ¹⁰ shell, are investigated with high resolution. The transitions from the 4d ⁹5p ², 4d ⁹5s6p, and 4d ⁹5snf (up to n = 9) configurations are identified and their autoionization widths are measured. Transitions from the highly excited 4d ¹⁰ ns (n = 8–10), 4d ¹⁰6p, and 4d ¹⁰7d configurations are also revealed and the ionization potential of Sn IV is refined. The data obtained are compared with the results of calculations by the Hartree-Fock and semiempirical methods.     

Spins and parities of low-lying states in 79Kr from the 78Kr(d,p)79Kr reaction

The structure of Kr has been investigated via the ⁷⁸Kr($\text{d}$, p)⁷⁹ Kr reaction using an isotopically enriched gas target and an 11.0 MeV vector-polarized deuteron beam. Differential cross sections, σ, and vector analyzing powers, A_y, have been measured from 25° to 95° for 10 proton groups below 2.5 MeV excitation energy. Comparisons of these distributions to DWBA calculations and empirical shapes were made to extract spectroscopic factors and values of spin and parity for these states.     

Instabilities of electron-hole plasma under impact ionization and microwave emission

The nonlinear stage of the evolution of electron—hole plasma instabilities in semiconductors under impact ionization (static differential conductivity σ_d > 0) is considered for the case of spatially uniform pertubations of density and electric field. If the differential mobility of carriers μ _d > 0, the instability arises only with allowance for the retardation of the process of impact ionization (linear theory of this effect was developed by M. Toda [4]). When μ _d < 0, the instability may appear in the absence of the retardation. Both these instabilities exhibit oscillating form and are due to h.f. negative dynamic differential conductivity. We determine time sweeps of the electric field under condition of fixed current for the case n-InSb at T = 77 K. The amplitude and the frequency (f>10¹⁰Hz) of the oscillations are evaluated and the conditions, when the shape of E(t)-oscillations is essentially non-harmonic, are determined. Microwave emission observed in semiconductors under impact ionization may have resulted from the instabilities at hand.     

Analysis of transitions from autoionization states of the Bi III, Bi IV, and Bi V ions

The spectra of transitions from the autoionization states of bismuth ions are studied in the wavelength region from 170 to 500 Å. More than twenty transitions from the levels of configurations accompanied by excitation of the inner 5d subshell in the Bi V, Bi IV, and Bi III ions are identified and their autoionization widths are measured. In addition, transitions from the highly excited 5d ¹⁰ np levels (n=8–11) in the Bi V ion are identified and the ionization potential is refined.     

Energy levels and probabilities of radiative transitions in the Kr IX ion

The energy levels of the 3d ⁹4l (l = 1–3) and 3p ⁵3d ¹⁰4l (l = 0, 1) configurations in the Kr IX ion and the probabilities of radiative transitions to the ground state from these excited states have been calculated within the relativistic perturbation theory using a zero-approximation model potential. The results are shown to be stable within this approximation. The well-known problem of anomalously low accuracy of the calculations of some higher lying singlet levels is considered.     

The vuv photoelectron spectra of atomic In and Tl

The photoelectron spectra of atomic indium and thallium have been obtained using a pseudo-atomic beam technique. Ionizations from the np, ns and (n ? 1)d shells (n = 5 for In and n = 6 for Tl) were observed using He(I) and HE(II) radiation. The (np)^?1 ionization results in a single ¹S₀ ionized state, whereas the (ns)^?1 and ((n ? 1)d)^?1 ionizations both result in states additional to those allowed for a one-electron ionization process. This is attributed to configuration interaction in the final ionized state.     

用于研究铝等离子体软X射线光谱的碰撞-辐射模型

我们建立了一个以AlXI和AlXII离子为主的碰撞一辐射模型,模型中考虑了碰撞电离和复合,碰撞激发和退激发,辐射复合和自发辐射跃迁等原子过程.本文还分析了该模型的计算结果,包括离子丰度分布,辐射损失,及诊断的特性.     

Testing of QED-Theory and Precise Measurements of the Rydberg Series for the He-Like Multicharged Ions

The wavelengths of the 1snp ¹ P ₁−1s ^{2 1} S ₀ transitions in He-like Mg XI, F VIII (n= 4–8) and Al XII (n=6,9) have been calculated in the framework of the 1/Z expansion method including relativistic effects and QED contributions. It is found that QED corrections to the ground-state ionization energy are significant at the present level of experimental accuracy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Excitation functions for the production of90Nb and88Y by irradiation of zirconium with deuterons

Excitation functions for reactions induced by deuterons on natural zirconium and⁹⁰Zr targets have been measured radiochemically with the stacked foil technique between ≈9 and 27 MeV. The observed reactions are Zr(d,xn)⁹⁰ Nb, Zr(d,axn)⁸⁸Y,⁹⁰Zr(d, 2n)⁹⁰Nb and⁹⁰Zr(d, α)⁸⁸Y. The excitation functions for the reactions⁹¹Zr(d, 3n)⁹⁰Nb and⁹¹Zr(d, αn)⁸⁸Y have been deduced from the results mentioned above. Calculations of the excitation function for the (d, 2n) reaction have been performed with two different treatments, each one taking into account two competitive mechanisms. The compound-statistical model plus Hittmair's stripping theory accounts quite well for the (d, 2n) cross sections observed. However, the agreement obtained with Peaslee-Otozai's theory is excellent and the set of parameters used more reasonable. It has been assumed that the stripping mechanism can have no contribution to the (d, α) reaction. Accordingly, calculations for this reaction have been done using the compound-statistical model and the entire absorption process followed by the evaporation of an α particle. No good agreement is obtained with either theory.     

Inner shell excitation and ionization of the monohalobenzenes

Energy loss (excitation) spectra of the gaseous monohalobenzenes, C ₆H ₅X (X = F, Cl, Br and I), were obtained by fast electron impact in the regions of the respective carbon 1 s, chlorine 2 p and 2 s, bromine 3 d and iodine 4 d edges. Gas phase X-ray PES measurements of the binding energies of these levels are also reported. Structure observed below the ionization limits has been interpreted with the aid of term values derived from the two sets of measurements.     

Pr3+ luminescence center in Lu2Si2O7 host

Pr³⁺‐doped Lu₂Si₂O₇ (LPS:Pr) microcrystalline phosphor was prepared by the sol–gel method. We study the LPS:Pr luminescence properties under UV and X‐ray excitation within 80–500 K. The emission spectrum is dominated by fast 5d–4f band peaking at 261 nm having 16 ns decay time. By purely optical contactless methods we determine the energy barrier of 300 meV for thermal ionization of the Pr³⁺ 5d₁ relaxed excited state in LPS host. The barrier is high enough to keep the room temperature quantum efficiency of the Pr³⁺ luminescence center close to unity. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quantum interference effects in field ionization: Application to the measurement of the fine structure splitting of highly excited Na2 D states

Quantum beats between the fine structure levels of highly excitedn ² D levels of sodium atoms have been measured by investigating the field electrons. The states were populated by stepwise excitation with two dye lasers and an electric field pulse was applied a certain time after the laser excitation. The quantum beat signal is observed when the time delay between excitation and ionization is varied. The fine structure splitting forn=21 to 31 has been measured.     

Low-temperature time-resolved VUV luminescence spectroscopy of SrF<Subscript>2</Subscript>: Er<Superscript>3+</Superscript> crystals

Time-resolved excitation and emission spectra of SrF₂: Er³⁺ upon selective excitation with synchrotron radiation in the VUV and ultrasoft x-ray ranges at T = 8 K were studied. The VUV luminescence of SrF₂: Er³⁺ derives from high-energy interconfiguration 4f¹⁰5d-4f¹¹ transitions in the Er³⁺ ion. The VUV emission spectrum revealed, in addition to the 164.5-nm band (millisecond-range kinetics), a band at 146.4 nm (with a decay time of less than 600 ps). The formation of excitation spectra for the f-f and f-d transitions in the Er³⁺ ion is discussed.     

Hybridization and electron interaction in nickel compounds

The bare Coulomb interaction, defined by the reaction 2dⁿ = d^n?1 + d^{n + 1} ? U is determined for some Ni compounds. It is found that U is larger than the 3d bandwidth even for metallic compounds. More relevant to the metal nonmetal transition is the optical gap energy E_G = U ? (E(3d^n?1) ? E(L)) where E(3d^n?1) and E(L) are the d-electron and ligand electron ionization potentials respectively.     

Interaction of trapped metastable excited He atoms with solid noble gases,Ne, Ar and Kr,investigated by EPR

Local metastable excited states are found in Ne, Ar and Kr cryocrystals as He gas-discharge products are trapped in the growing cryocrystals. These states are detected by EPR and are interpreted as being local metastable excitednp⁵(n+1)s³P₂ atomic-type states in Ne, Ar and Kr cryocrystals. Analysis of the results allows the following explanation of the observed effect to be given. For the Ne cryocrystal the effect is interpreted as a new phenomenon: quasi-resonance transfer of excitation energy from the metastable He 2³S₁ atom trapped in a growing neon cryocrystal to the exciton energy band of the neon crystal followed by the exciton self-trapping into the 2p⁵3p state and subsequent decay, ending in the 2p⁵3s³P₂ state recorded by EPR in our experiment. In the case of Ar and Kr cryocrystals the effect is explained as being due to an internal ionization of the cryocrystals by the excitation energy of trapped metastable He atoms, which implies the formation in the cryocrytal of a Rg⁺ ion and a free electron in the conduction band, whereupon the fast (of 10^?12 s) self-trapping reaction of a hole follows: Rg⁺+Rg→Rg ₂ ⁺ . Thereafter the dissociative recombination reaction Rg ₂ ⁺ +e→Rg ₂ ^** →Rg+Rg*(³P₂) could take place.     

Velocity dependence of total Penning ionization cross sections

The velocity dependence of the total Penning ionization cross sections,σ(v), is measured in the thermal relative velocity region, using a time of flight method.σ(v) curves are reported for the collision systems He(2¹ S)/Ar, Kr, Xe, N₂, Hg, He(2³ S)/Ar, Kr, Xe, N₂, Hg, Ne(³ P _{2, 0})/Kr, Hg, and Ar(³ P _{2, 0})/Hg. In a qualitative discussion it is shown that all features of the measuredσ(v) curves may be explained within the frame of the theory of Penning ionization, allowing to extract information on the physical quantities governing the process: on the interaction potentialV(R) and on the transition probabilityW(R). A theoretical calculation for the He(2³ S)/Ar system shows good agreement with our experimentalσ(v) curve. On the basis of the present results earlier data onσ(v), and on absolute cross sections and rate constants obtained at certain relative velocity distributions are discussed.