Valence band x-ray emission spectra of compressed germanium

We report measurements of the valence band width in compressed Ge determined from x-ray emission spectra below the Ge K edge. The width of the valence band does not show any pressure dependence in the semiconducting diamond-type structure of Ge below 10 GPa. On the other hand, in the metallic beta-Sn phase above 10 GPa the valence band width increases under compression. Density-functional calculations show an increasing valence band width under compression both in the semiconducting phase (contrary to experiment) and in the metallic beta-Sn phase of Ge (in agreement with observed pressure-induced broadening). The pressure-independent valence band width in the semiconducting phase of Ge appears to require theoretical advances beyond the density-functional theory or the GW approximation.     

The effect of the core hole on x-ray emission spectra in simple metals

We show that one-particle calculations of x-ray spectra with and without the core hole can give drastically different results, indicating a breakdown of one-particle theory. Only emission spectra obtained in the absence of the core hole consistently show a close resemblance to experiment. We show, that this fact can be explained by the many-body theory of Nozières and DeDominicis. We are then able to give the first interpretation of the L_2,3 satellite spectrum of sodium.     

相对标定电荷交换复合谱及束发射谱测量杂质浓度的方法研究

采用数值模拟方法计算了HL-2A装置上电荷交换复合谱和束发射谱的强度,并根据两种光谱的比值得到碳和氦杂质的浓度,与初始假设对比后验证了该方法理论上的可靠性。实验上采用一台三光栅光谱仪系统,利用同一视线、同时测量了碳(CⅥ)、氦(HeⅡ)的电荷交换复合谱及中性束发射谱,首次在HL-2A装置上同步获得了C6+、He2+离子的绝对浓度剖面。该方法采用了相对强度标定而非复杂的绝对强度标定,并且避免了中性束衰减计算。     

Intensity of high energy plasmon satellites band in soft x-ray emission spectra

Using Bohm and Pines theory of plasma oscillations in solids the relative intensities of the Mg K^V_β and Al K^VI_β satellites have been estimated as 0.89% and 0.61% respectively. These values are in close agreement with the experimental values reported by Kunzl.     

The electronic structure,x-ray photoelectron and emission spectra of YOF

The results of electronic structure calculations for YOF are presented, making use of Xα-DVM together with experimental X-ray photoelectron and emission spectra for this compound. Three versions of calculations have been performed, depending on the relation between oxygen and fluorine charges in the [YO₄F₄] cluster. The interpretation of experimental spectra is carried out on the basis of these calculations.     

Calculation of soft x-ray emission spectra of aluminium by APW method

In this paper an ab initio calculation of the shapes of emission bandsK andL _{2, 3} of aluminium is described, which is based on the band structure recently determined by the APW method [1]. The expression for the transition probability is derived under the assumption that wave functions of valence electrons are linear combinations of APW functions, whereas wave functions of core electrons are approximated by Bloch sums of atomic functions. A method analogous to that of Gilat and Raubenheimer is used to determine the shapes of spectra. The influence of transition probability and Auger effect are discussed, and the results of calculations are compared with experimental data.     

The electron structure and x-ray emission spectra of noble metal aluminides

A calculation of the electron structure of [Al₈Cu₄] and [Al₈Au₆]- clusters was performed by the XαSW SCF-method. The X-ray emission and photoelectron spectra for noble metal aluminides Al₂Cu and Al₂Au are interpreted on the base of these calculations. The question of the possible influence of d-states on the distribution of Al3s-states and the shape of the AlL_2,3-emission spectrum is discussed for Al₂Cu.     

On the origin of soft x-ray and microwave sources of emission in solar magnetic loops

One possible mechanism is proposed for the appearance of high-temperature sources of emission in solar magnetic loops visible sometimes in the microwave and soft x-ray bands in active regions, even out of flares. The main concept of this mechanism is as follows. Due to the existence of current in the magnetic loop, there is a component of the electric field E which is longitudinal to the magnetic field. In this case, at some heights the parameters of solar atmospheric plasma (density and temperature) appear to cause a certain number of electrons to be in a runaway regime. These electrons can be accelerated to energies of about 1–2 keV. This corresponds to the temperature of the observed microwave and x-ray source. Accelerated electrons satisfying the trapping condition will gradually fill the magnetic tube, and after a while a hot x-ray loop can occur. Similar mechanisms of the appearance of hightemperature sources of emissions in active regions probably take place in the simple loop flare for the class of thermal flares visible in the microwave and soft x-ray bands.Department of Astrophysics and Cosmic Plasma Physics, Applied Physics Institute, Russian Academy of Sciences, Nizhnii Norgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 7, pp. 836–850, July, 1994.     

Anisotropy of x-ray emission spectra and electronic structure of V2O5 single crystals

The results of investigation of x-rayVK- andVL-emission spectra orientation dependence for V₂O₅-single crystals are reported. The applicability of different options of electronic structure cluster calculations for the interpretation of x-rayVK-emission bands anisotropy in V₂O₅-single crystal is discussed.     

Relative intensities in x-ray photoelectron spectra

An experimental determination of the relative intensities of X-ray photoelectron lines corresponding to the inner levels of elements with Z ? 20, and calculations of the total photo-ionization cross-sections for all shells of these elements with the Hartree—Fock—Slater potential are reported. The experimental and theoretical values agree well for the 1s levels while marked discrepancies are revealed for the 2p levels. The theoretical values of the cross sections for the atomic valence levels are used to calculate the relative intensities of molecular levels in CF₄, BF₄^?, BeF₄^2?, LiF, NO₃^?, CO₃^2?, CO, N₂, CO₂, H₂O and C₄H₅N. The results of the calculations agree satisfactorily with experiment.     

On the possibility of investigating the dispersion of the energy bands of a crystal using resonant x-ray emission spectra

It is shown that, when the dispersion of the energy bands of crystals is investigated by resonant x-ray emission (RXE), an ambiguity can arise in the determination of k _tr — the transition point in k space — as a result of the characteristic features of the band structure and the value of the matrix elements. It is proposed that calculations of the distribution of partial contributions to interband optical transitions in the Brillouin zone (BZ) be used as a means of obtaining a simplified estimate of k _tr. The basic properties of this distribution are examined for lithium hydride, which is a convenient model object having a simple band structure and interband transitions which have been studied in detail. It is shown that the k points of the general position, which form a complex figure in the BZ, make the main contribution to the interband transitions. The contribution of high-symmetry points is much smaller mainly because of their small representativeness. This make it easier to understand the reason for the possible nonmonotonic variation of k _tr in RXE measurements of the dispersion of the energy bands of crystals or the sharp changes in the resonance-fluorescence intensity. Fiz. Tverd. Tela (St. Petersburg) 41, 1597–1601 (September 1999)     

Relative line intensities in the argon L x-ray emission spectra produced by 0.3 to 3 keV electron impact

This note presents the first measurement of the relative intensities of the radiative processes of the L shell of argon. The partial emission cross sections are deduced. Our data show that the radiative transitions within the excited ion are very sensitive to the incident electron energy.     

Some expected anomalies in the impurity vibronic spectra of ferroelectrics

The influence of the soft phonon branch on some characteristics of the impurity vibronic absorption spectra in ferroelectrics is qualitatively analyzed and illustrated using simple models. The following quantities are discussed: the intensity, the temperature shift and the half width of the no-phonon line, the one-phonon wing, the integral intensity of a parity forbidden band. It is shown that near the phase transition point (T > T_c) all these characteristics must show anomalous dependencies on temperature, if compare with usual matrix crystals. The observation of “plateaus” may be expected in these dependencies. Various aspects of obtaining information from measured impurity vibronic spectra of ferroelectrics are discussed.     

空心原子的K-x射线谱

报道了利用兰州重离子加速器国家实验室ECR离子源首次引出的全裸Ar离子和类氢、类氦、类锂Ar离子与Be固体表面相互作用形成的空心原子x射线实验测量结果.结果发现，同样条件下，由于K壳层电子的剥离，Ar的K-x射线单离子发射产额增加了5个量级，约为36×10-3每原子；而当L壳层存在电子时，Ar的K-x射线几乎观测不到. 关键词： 高电荷态离子 空心原子 x射线 单离子产额     

New screening doublets in x-ray satellite spectra

Recent scrutiny of the relevant data available at present on x-ray satellite spectra in theK, L andM regions revealed the existence of two new satellite pairsα″α′ andα″α′ ₃ ′ in theKα satellite group, three pairsα′ ₂ α″,α′ ₂ α^VI andα? α ^IV in theLα satellite group, twoLβ ₂ satellite groups; viz.,β ₂ ^(b) (β ₂ ^I ,β ₂ ^II β ₂ ^(c) ) andβ ₂ ^(c) (β ₂ ^I β ₂ ^II ), two pairsγ′₁ γ′₂ andγ′₁ γ′_2′ in theLγ satellite group and also a pairβ _II β _III in theMβ satellites, which are all found to be governed by the screening doublet relationship,Δ(v/R)^1/2=constant.