Negative-parity spectra for mass-18 nuclei in the dynamic-interaction propagator approach

The energy spectra and two-particle strengths of negative-parity states in mass-18 nuclei are calculated by using a Green-function formulation which includes energy-dependent two-particle interactions. The energy dependence is induced by the dynamic exchange of the octupole phonon which appears at 6.13 MeV in ¹⁶O. This state is described within a normal static particle-hole RPA. The two-body interaction parameters are chosen to provide the correct phonon energy and reasonable negative parity mass-17 and positive-parity mass-18 spectra. The negative-parity states are then calculated in a parameter-free way. In order to avoid redundant solutions or ghosts, the fermion lines must be dressed in a way consistent with the phonon exchange.     

Polarization entangled photons at x-ray energies

We show that polarization entangled photons at x-ray energies can be generated via spontaneous parametric down-conversion. Each of the four Bell states can be generated by choosing the angle of incidence and polarization of the pumping beam.     

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.     

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.     

Laser produced soft x-ray spectra of silver

Spectral lines corresponding to the transitions 3d¹⁰4s - 3d¹⁰np, 3d¹⁰4s² - 3d¹⁰4snp and 3d¹⁰4s²4p - 3d¹⁰4s²nd, 3d¹⁰4s²ns of Ag XIX - Ag XVII have been identified in a laser produced soft X-ray spectrum of silver by computing the transition energies with the help of a self-consistent field, Hartree-Fock-Slater code and by extrapolation of our previous observations regarding the state of ionization of the plasma in the cases of Mg, Al, Fe and Cu.     

First-principles calculations of K-shell x-ray absorption spectra for warm dense ammonia

The x-ray absorption spectroscopy is a powerful tool for the detection of thermodynamic conditions and atomic structures on warm dense matter. Here, we perform first-principles molecular dynamics and x-ray absorption spectrum calculations for warm dense ammonia, which is one of the major constituents of Uranus and Neptune. The nitrogen K-shell x-ray absorption spectrum(XAS) is determined along the Hugoniot curve, and it is found that the XAS is a good indicator of the prevailing thermodynamic conditions. The atomic structures at these conditions are ascertained. Results indicate that the ammonia could dissociate to NH_x(x = 0, 1, or 2) fragments and form nitrogen clusters, and the ratios of these products change with varying conditions. The contributions to the XAS from these products show quite different characteristics,inducing the significant change of XAS along the Hugoniot curve. Further model simulations imply that the distribution of the peak position of atomic XAS is the dominant factor affecting the total XAS.     

Polarization dependent absorption spectra in quantum wire structures

The band mixing effect in the valence band of quantum wire structures (QWS) was analyzed. The effective mass of the lowest subband in the wire-axis direction was found to be as small as 0.027 m₀ at the band edge for the first time. This reduced effective mass and the related nonparabolicity of the subband structure play a significant role in determining the exciton properties. The influence of the subband nonparabolicity is shown to be larger for the QWS with a larger cross section because of the reduction of the energy separations and the resultant interactions among the subbands. The dependence of the exciton matrix element on the polarization of the incident photon is discussed.     

Single-order soft x-ray spectra with spectroscopic photon sieve

A single-order diffraction transmission grating named spectroscopic photon sieve(SPS) for soft x-ray region is proposed and demonstrated in this paper. The SPS consists of many circular pinholes located randomly, and can realize both free-standing diffractions and the suppression of higher-order differations. In this paper, the basic concept, numerical simulations, and calibration results of a 1000-lines/mm SPS for soft x-ray synchrotron radiation are presented. As predicted by theoretical calculations, the calibration results of a 1000-lines/mm SPS verify that the higher-order diffractions can be significantly suppressed along the symmetry axis. With the current nanofabrication technique, the SPS can potentially have a higher line density, and can be widely used in synchrotron radiation, laser-induced plasma diagnostics, and astrophysics.     

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.     

Polarization dependence of the infrared spectra of TlSbS2

We report an investigation of the long wavelength phonons of TlSbS₂ performed by far-infrared Fourier transform spectroscopy. In close agreement with our previous Raman work, we find strongly polarized data. Significant differences appear between the two set of infra-red and Raman frequencies which correlate well with the centrosymmetric character of some of the linear units which couple to constitute the layer.