Peak Of X-ray Emission Research Articles

Photoelectron and X-ray spectroscopy of minerals. Part 1.—Electronic structure of forsterite (magnesium orthosilicate)

X-ray emission (Si Kβ1,3, Si L2,3M, Mg Kβ1,3 and O Kα) and X-ray photoelectron spectra are presented for forsterite (Mg2SiO4) and aligned on a common energy scale using core ionisation energies. The energies and relative intensities of peaks in these spectra are discussed in terms of possible theoretical models for SiO4–4: ab initio, Xα etc. The magnesium Kβ X-ray emission peak profile and position relative to oxygen Kα shows that the O—Mg bond is more ionic than O—Si. The spatial position of magnesium ions relative to silicate anions would appear to facilitate σ—π mixing, i.e. the mixing of orbitals which to a first approximation could be regarded as either O—Si bonding or oxygen lone pairs.

Properties of flares observed in the Mg i b2 line at 5172 �

Observations of emission in the Mgi b2 line at 5172 A are presented for 13 flares. Also discussed are 3 flares which occurred in regions under observation but which showed no Mg emission. The Mg flare kernels resemble white-light flare kernels in their general morphology and location. Comparison of Mg filtergrams with magnetograms indicates that the Mg kernels occur at the feet of magnetic arches across neutral lines. Time-lapse Mg filtergram films indicate photospheric shearing motions near flare sites for several hours before flare onset. We have compared flare Mg emission with microwave and both hard and soft X-ray flare emissions. Examination at the time development of the 1981, July 27 flare shows that the microwave and X-ray bursts may be clearly related to the appearance of successive Mg flare kernels. We have also compared subjective, relative Mg flare importances with other flare emission measurements. For the full sample of flares, Mg importance is significantly correlated with hard and soft X-ray emission peaks, with X-ray ‘hardness’ (ratio of hard to soft peaks) and with the rise slope of soft X-ray bursts. The Mg importance does not correlate with the microwave peaks when the full sample of flares is used, but for the subset showing Mg emission there is significant correlation. No correlation with Hα importance was found. Our results suggest that Mg emission is associated with an impulsive component which may be absent from some flares. The San Fernando Observatory magnesium etalon filter system is described.

Resolution enhancement for a commercial X-ray fluorescence spectrometer

The construction of an additional collimator is described which removes asymmetric long wavelength tails from X-ray emission peaks. The resulting spectra can be subjected to deconvolution procedures, based on Fourier analysis, which reduce the broadening due to the primary collimator. The final spectra are very similar, in quality and resolution, to those obtained from double crystal spectrometers.

An X-ray map of SN 1006 from the Einstein Observatory

An X-ray map of the SN 1006 supernova remnant acquired by the imaging proportional counter of the Einstein Observatory in the energy range 0.1-4 keV is presented. The image obtained from the imaging proportional counter shows a limb-brightened nebula, almost circular in outline with enhanced emission in two quadrants. The hardness ratio map reveals a large range of temperatures over the object, with the highest values near the limbs of the enhanced emission regions. Consideration of a three-dimensional model of the object indicates the presence of a shell of electron temperature varying between 10 to the 6th and 10 to the 7th K and density varying between 0.3 and 6/cu cm surrounding a fairly uniform interior, of electron temperature 1.5 x 10 to the 6th K and density 1.0/cu cm. The optical filaments are observed to lie parallel with the faintest edge of the X-ray shell, about 1 arcmin from the peak of X-ray emission. Mass visible in the X-ray image of 5-15 solar masses suggests that the supernova may have been of type II. No evidence is obtained for a hot stellar remnant.

X-ray emission from supernova remnants near gamma-ray sources

view Abstract Citations (57) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-ray emission from supernova remnants near gamma-ray sources. Lamb, R. C. ; Markert, T. H. Abstract It is noted that the imaging proportional of the Einstein Observatory has been used to search for X-ray emission from eight radio supernova remnants which are near three of the Cos-B unidentified gamma-ray sources: 2CG 311-01, CG 327-0, and CG 333+0. Emissions are observed from three of the remnants and upper limits on the remainder which are consistent with the luminosity expected from a simple blast-wave heated plasma model of the process. Thus none of the remnants are superluminous as might be expected if the pattern of the Crab Nebula were followed. It is thought that the remnant RCW 103 may be Vela-like. It is noted that another of the remnants, Kes 27, has centrally peaked X-ray emission which is unlike the shell-like emission seen for many remnants and which does not correlate well with its asymmetric radio emission. Publication: The Astrophysical Journal Pub Date: February 1981 DOI: 10.1086/158688 Bibcode: 1981ApJ...244...94L Keywords: Gamma Ray Astronomy; Nebulae; Supernova Remnants; X Ray Sources; Neutron Stars; Point Sources; Proportional Counters; X Ray Telescopes; Astronomy full text sources ADS | data products SIMBAD (15)

Electronic structure of iron(II) and (III) fluorides using X-ray emission and X-ray photoelectron spectroscopies

Iron(II) and (III) fluorides have been studied using X-ray emission (XE) and photoelectron (XP) spectroscopies. XE data enable the XP peaks to be identified unequivocally; in the iron(III) compound the F 2p and Fe 3d orbitals were shown to have almost identical energy. The F Kα XE peak profile showed the Fe–F band to be more covalent in ferric than ferrous fluoride. Whilst the F 1s binding energy was the same for both compounds a peak shift of 3.0–3.5 eV to higher binding energies was found for all iron orbitals upon oxidation. The rapid reduction of iron(III) to iron(II) by argonion bombardment was observed.

The Ll and Lη X-ray emission spectra of some first-row transition metals and compounds

The Ll and L eta X-ray emission spectra for Mn, Fe, Ni and Cu elements and in simple compounds excited by secondary radiation, are presented and compared with corresponding spectra from Zn, ZnO and Ga2O3. Variations in the Ll:L eta intensity ratio, which is often found to be very much less than the theoretical value of 0.5, are ascribed to the intervention of the Auger process L2L3M4,5 which effectively converts L2 holes into L3 holes; it is assumed that a 3d spectator hole will not affect the energy of a 3s to 2p transition. Chemical factors considerably affect the probability of the L2L3M4,5 Auger process so that in the case of ferricyanide, for example, Ll:L eta =0.46. A comparison is made between the structure of L eta and Ll X-ray emission peaks and 3s and 2p peaks in X-ray photoelectron spectra.

The electronic structure of magnesium dialuminium tetraoxide (spinel) using X-ray emission and X-ray photoelectron spectroscopies

The Mg-Kβ1,3, O-Kα1,2, and Al-L2,3X-ray emission spectra and also the X-ray photoelectron spectrum of spinet, MgAl2O4, are reported. A model for the bonding is derived using simple molecular-orbital theory, which is adequate for a qualitative rationalisation of the observed spectra. The shape of particular X-ray emission peaks is shown to be strongly dependent on the bonding commitments and co-ordination of the emitting atoms.

Direct evidence for the quadruple metal–metal bond in the octachlorodimolybdenum(II) ion, [Mo2Cl8]4–, using X-ray emission spectroscopy

Analysis of the MoLβ2,15(d–2p)X-ray emission peak from [Mo2Cl8]4– shows the presence of three molecular orbital energy levels, contributing to the Mo–Mo quadruple bond, together with a peak at a higher binding energy which is attributed to Mo–Cl bonding orbitals.

X-Ray emission and photoelectron spectra from magnesium oxide: a discussion of the bonding based on the unit Mg4O4

A simple molecular-orbital model for the bonding in magnesium oxide is developed using Mg4O4(a cube with magnesium and oxygen atoms at alternate corners) as a basis. Extension to Mg32O32 indicates how the molecular-orbital description of Mg4O4 can be developed into the band structure for MgO. The qualitative predictions concerning the distribution of Mg 3p, Mg 3s, O 2p, and O 2s character amongst the various orbitals are checked by comparison with X-ray emission (Mg-Kβ1,3, Mg-L2,3 M, and O-Kα) and also X-ray photoelectron spectra. The Mg4O4 model provides an adequate rationalisation of the principal features of the spectra, particularly of the split magnesium X-ray emission peaks.

The detection of light elements by X-ray emission spectroscopy with use of low-energy satellite peaks

A method for the indirect detection of light elements, L(L C, N, O or F), by using X-ray emission spectroscopy is described. The technique relies upon the formation of certain low-energy satellite peaks to those X-ray emission peaks which originate from electronic transitions involving the valence shell of an element, A, when A—L bonds are made. The energy difference between the main peak and the satellite peak is characteristic of the ligand (F, 20 ± 1 eV; O, 14 ± 2 eV; N, 9 ± 2 eV; and C, about 5 eV). Applications to compounds that contain more than one type of ligand are described and experimental limitations are discussed.

鉄-クロム合金における介在物の生成挙動

It is necessary to analyse the fomation behaviour of tetragonal chromite from the crystallographical and technological viewpoints.Various physical means such as high temperature X-ray, Massbauer resonance and X-ray emission peak shift studies have been employed in this investigation.Results obtained were as follows:1) Mössebauer resonanse study indicate that all the tetragonal chromites have quadrupole splitting. The value becomes larger as the tetragonality of chromite increases. This tendency agrees with the Crka doublet shift study. It is also found that the existence of Cr2+, may disturb the cubic symmetry in the chromite crystal field.2) From the high temperature X-ray diffraction study, it was found that the experiment at lower temperature such as 100-200°C should be performed precisely to pursue whether Jahn-Teller effect contributes to tetragonal chromite.3) Chromium content in the inclusions extracted from the high-chromium alloys is over the stoichiometric composition of FeCr2O3. This fact agrees with the results obtained from the synthesis of the tetragonal chromite.

Observations of energetic X-rays and solar cosmic rays associated with the 23 May 1967 solar flare event

On 23 May 1967 energetic (10–50 keV) solar flare X-rays were observed by the OGO-III ion chamber during the period 1808–2100 UT. The time-intensity profile for the X-ray event showed three distinct peaks at ≈1810, 1841 and 1942 UT. The second peak, which is equivalent to ≈2.9 × 10−3 ergs cm−2sec−1 above 20 keV, is the largest X-ray burst observed so far by the OGO-I and OGO-III ion chambers. The soft (2–12 A) X-ray observations reported by Van Allen (1968) also show similar peaks, roughly proportional in magnitude to the energetic X-ray peaks. However, the intensity of energetic X-rays peaked in each case 5–10 min earlier than the soft X-ray intensity indicating a relatively hard photon energy spectrum near the peak of the energetic X-ray emission. The corresponding time-intensity profile for the solar radio emission also showed three peaks in the microwave region nearly coincident with the energetic X-ray peaks. The third radio peak was relatively rich in the metric emission. Beyond this peak both the energetic X-rays and the microwave emission decayed with a time constant of ≈8 min while the corresponding time constant for the soft X-rays was ≈43 min. In view of the earlier findings about the energetic X-rays it is indicated that the 23 May solar X-ray event was similar to those observed earlier. During the 23 May event the integral energy flux spectrum at the time of peak intensity is found to be consistent with the form ∼e −E/E 0, E 0 being about 3.4 and 3.7 keV for the peaks at 1841 and 1942 UT, respectively. Assumption of a similar spectrum during the decay phase indicates that the spectral index E 0 decreased nearly exponentially with time.