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[en] We have measured the polarization of the intercombination line 1s3p 3P1-1s21S0, the so called Kβ2 line, in helium-like V21+ using two Bragg crystal spectrometers. The ions were excited in the Lawrence Livermore National Laboratory electron beam ion trap. We find values which are not significantly different from theoretical predictions based on some admixing of the initial state by the hyperfine interaction. In this short paper we present our results
[en] The intensity of the polarized Ly-α1 (2p3/2 → 1s1/2) transition has been measured relative to that of the unpolarized Ly-α2 (2p1/2 → 1s1/2) transition in Fe25+. The measurements were made with the Livermore electron beam ion trap EBIT-II for beam energies from threshold to 2.5 times threshold. The results are compared to the corresponding intensity ratio predicted using excitation cross sections from distorted-wave calculations, which includes polarization, the M1(2s1/2 → 1s1/2) transition, and cascade contributions. Discrepancies are found that tend to confirm a recent report of a measurement of the Ly-α lines in Ti21+ performed on the Tokyo electron beam ion trap
[en] Fe XVII x-ray emission is present, in a multitude of sources, such as the corona of the Sun, Capella, and Procyon. Two of the strongest lines observed in these spectra are the resonance and intercombination lines located at 15.01 and 15.26 (angstrom), respectively. As part, of the laboratory astrophysics program at the electron beam ion traps EBIT-I and EBIT-II located at the Lawrence Livermore National Laboratory we have measured this line ratio for the case where the relative abundance of Fe XVI to Fe XVII is ∼ 1. Our results show that an Fe XVI innershell satellite line coincides with the intercombination line and can significantly reduce the relative intensity, R, of the resonance to intercombination line. The fact that the apparent, relative intensity of the resonance and intercombination line in Fe XVII is sensitive to the strength of an Fe XVI innershell satellite, and therefore, the relative abundance of Fe XVI to Fe XVII, makes the line ratio a diagnostic of temperature, and explains the anomalously low ratios observed in the solar and stellar coronae
[en] We have measured the collisional excitation cross sections for the 3d→4f and 3d→5f excitations in Au ions near the Ni-like charge state by using beam plasmas created in the Livermore electron beam ion trap EBIT-I. The cross sections have been experimentally determined at approximately 1, 2 and 3 keV above the threshold energy, ET, for the 3d→4f excitations (ET ~2.5 keV) and at approximately 0.1, 1 and 2 keV above the threshold energy for the 3d→5f excitations (ET ~3.3 keV). The cross section measurements were made possible by using the GSFC x-ray microcalorimeter at the Livermore EBIT facility. The absolute cross sections are determined from the ratio of the intensity of the collisionally excited bound-bound transitions to the intensity of the radiative recombination lines produced in EBIT-I plasmas. The effects of polarization and Auger decay channels are accounted for in the cross section determination. Measured cross sections are compared with those from HULLAC, DWS and FAC calculations. Finally, the measurements demonstrate that some errors exist in the calculated excitation cross sections.
[en] We have measured the polarization of the 2p3/2→1s1/2 Lyman-α1 x-ray line of hydrogenlike Ar17+ and Fe25+ at electron-impact energies ranging from 7 to 25 threshold units. The highly charged argon and iron ions were produced using the Lawrence Livermore National Laboratory SuperEBIT electron beam ion trap. A combination of two crystal spectrometers and a microcalorimeter were used to record the Lyman-α x-ray emission of Ar17+ and Fe25+ and to infer the polarization of the Lyman-α1 line. Our results show a systematic discrepancy with the predictions of distorted-wave calculations