Energy Shift Of Lines Research Articles

Phase-resolved spectroscopy of a quasi-periodic oscillation in the black hole X-ray binary GRS 1915+105 with NICER and NuSTAR

ABSTRACT Quasi-periodic oscillations (QPOs) are often present in the X-ray flux from accreting stellar-mass black holes (BHs). If they are due to relativistic (Lense–Thirring) precession of an inner accretion flow which is misaligned with the disc, the iron emission line caused by irradiation of the disc by the inner flow will rock systematically between red and blue shifted during each QPO cycle. Here, we conduct phase-resolved spectroscopy of an ∼2.2 Hz type-C QPO from the BH X-ray binary GRS 1915+105, observed simultaneously with NICER and NuSTAR. We apply a tomographic model in order to constrain the QPO phase-dependent illumination profile of the disc. We detect the predicted QPO phase-dependent shifts of the iron line centroid energy, with our best fit featuring an asymmetric illumination profile (>2σ confidence). The observed line energy shifts can alternatively be explained by the spiral density waves of the accretion-ejection instability model. However, we additionally measure a significant (>3σ) modulation in reflection fraction, strongly favouring a geometric QPO origin. We infer that the disc is misaligned with previously observed jet ejections, which is consistent with the model of a truncated disc with an inner precessing hot flow. However, our inferred disc inner radius is small (rin ∼ 1.4 GM/c2). For this disc inner radius, Lense–Thirring precession cannot reproduce the observed QPO frequency. In fact, this disc inner radius is incompatible with the predictions of all well-studied QPO models in the literature.

Probing Extragalactic Planets Using Quasar Microlensing

Abstract Previously, planets have been detected only in the Milky Way galaxy. Here, we show that quasar microlensing provides a means to probe extragalactic planets in the lens galaxy, by studying the microlensing properties of emission close to the event horizon of the supermassive black hole of the background quasar, using the current generation telescopes. We show that a population of unbound planets between stars with masses ranging from Moon to Jupiter masses is needed to explain the frequent Fe Kα line energy shifts observed in the gravitationally lensed quasar RXJ 1131–1231 at a lens redshift of z = 0.295 or 3.8 billion lt-yr away. We constrain the planet mass-fraction to be larger than 0.0001 of the halo mass, which is equivalent to 2000 objects ranging from Moon to Jupiter mass per main-sequence star.

Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5–10 fs slow modulations. These features indicate the coexistence of two general processes of the light–matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. An intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.

GALACTIC Al 1.8 MeV GAMMA-RAY SURVEYS WITH INTEGRAL

26 Al is a long-life radioactive isotope with a half lifetime of near 1 Myr. The origin of Galactic 26 Al is dominated by massive stars and their core-collapse supernovae. Detections of 1809 keV emission from 26 Al provide direct evidence that nucleosynthesis is ongoing in the Galaxy. The gamma-ray line shapes reflect the dynamics of the ejected isotopes in the interstellar medium and then probe properties of ISM and Galactic rotation effect. Gamma-ray emissions of 26 Al in the Galaxy are studied with the high spectral resolution INTEGRAL spectrometer (SPI). We carry out the first spectral survey of 26 Al gamma-ray line emission along the Galactic plane. The 26 Al line energy shifts reflect the large-scale Galactic rotation. The 26 Al intensity is brighter in the 4th than in the 1st quadrant (ratio ~ 1.3); the 26 Al line toward the direction of the Aquila region appears somewhat broadened; a latitudinal scale height of [Formula: see text] pc for 26 Al in the inner Galaxy is determined. Strong 26 Al emission signal is detected in the nearby star-formation regions Sco-Cen and Cygnus. The 26 Al line shapes in star-formation regions provide a clue to constrain the kinematic properties of ISM. In addition, we derive the flux ratio of 60 Fe /26 Al ~ 15% which can be directly compared with theoretical predictions. More theoretical work on nuclear reactions, massive star evolution models deserves improvements.

Excitation dynamics and post-collision interaction for lowest autoionizing states in Li and Li2 excited by electron impact

The ejected-electron spectra in the region of the lowest autoionizing states in Li and have been studied at an observation angle of 54.7° over the electron-impact energy range 0–6 eV above the excitation threshold at 56.4 eV. The strong near-threshold resonance excitation has been revealed for the and (1s → 3σg)1Σ+g molecular transitions. For the atomic , and molecular states the post-collision interaction (PCI) energy shift of corresponding lines has been measured and compared with electron-impact excitation functions for these states. The general appearance of the PCI data for the and states reveals a close agreement with the classical and semi-classical predictions, showing a minimal correlation between resonance excitation of the subshell and the PCI. Meanwhile, in the energy region of 0–1 eV the energy shift of the line reveals an abrupt decrease to nearly zero values, similar to that observed earlier for the (np5(n+1)s2)2P3/2 lines in the ejected-electron spectra of Na (n = 2) and K (n = 3) atoms. The calculations show the possibility for extrema of the PCI shift to appear in those energy regions where the negative-ion resonances are present in the excitation function of the state.

The post-collision energy shift of the (np5(n + 1)s2)2P3/2 lines in autoionizing spectra of sodium (n = 2) and caesium (n = 5) atoms excited by electron impact

The energy shift of lines arising from the decay of the (np5(n + 1)s2)2P3/2 autoionizing states in Na (n = 2) and Cs (n = 5) atoms has been studied for the first time in ejected-electron spectra measured over the excess energy range −0.1 to 5.4 eV. In Na spectra, the energy dependence of the shift possesses a clear oscillatory-like character. In particular, the shift becomes of negative or positive sign depending on the presence or absence of a negative-ion resonance structure in the excitation function of the (2p53s2)2P3/2 state. Earlier, we reported a similar behaviour of the line shift for the (3p54s2)2P3/2 autoionizing state in K atoms. Though in Cs atoms the strong negative-ion resonance is also present close to the excitation threshold of the (5p56s2)2P3/2 state, in contrast to Na and K data, the energy dependence of the line shift possesses a smooth asymptotic behaviour described well by the classical model of the post-collision effect. The comparative analysis of the spectroscopic classification of the resonance structure in the excitation of the (np5(n + 1)s2)2P3/2 autoionizing states in Na, K and Cs atoms has shown that the observed effect most probably reflects the complication of the compound character of resonances. In whole, the obtained data show that under the condition of the high polarizability of a resonantly excited target the relation between polarization attraction, centrifugal and Coulomb repulsion becomes a crucial factor which determines the final energy distribution of outgoing electrons.

Post-collision interaction in electron impact excitation of the p6 outer subshell in Na, K, and Cs atoms

The post-collision interaction (PCI) energy shift of lines resulting from the decay of the np5(n+1)s22P3/2 lowest autoionizing states has been measured in the ejected-electron spectra of Na, K, and Cs atoms. The data reveal several new features in the energy dependences of the line shift. Particularly, contrary to the smooth asymptotic character predicted by the known models of the PCI, the oscillations of the shift are observed in Na and K atoms. The oscillations appear in those energy regions where the strong negative-ion resonances are present in excitation functions for the np5(n+1)s22P3/2 states. Despite the strong resonance excitation of the 5p56s22P3/2 state in Cs atoms, the respective PCI shift satisfies the classical description of the effect.

Dynamics of post-collision interaction in the near-threshold electron excitation of the (3p54s2)2P3/2,1/2 autoionizing states in potassium

The post-collision interaction (PCI) energy shift of lines corresponding to the decay of the (3p54s2)2P3/2,1/2 lowest autoionizing states in potassium atoms was studied by precisely measuring the ejected-electron spectra in the excess energy range between 0 and 3.5 eV. The energy dependence of the line shift for both states reveals a complicated character. In particular, instead of the smooth asymptotic behaviour predicted by available models of PCI, the shift can possess both positive and negative sign in an excess energy region between 0.2 and 1.3 eV. Comparison of these data with the near-threshold excitation cross sections of the (3p54s2)2P3/2,1/2 states showed that such behaviour is observed in the same energy regions where the negative-ion resonance structure is present in excitation functions. To explain the observed features, the effect of core-polarization on the final energy distribution of outgoing electrons is considered and the possibility of the negative line shift for the and states is shown by numerical evaluation.

Study of Long-lived Radioactive Sources in the Galaxy with INTEGRAL/SPI

The large-scale spectral characteristics of both 26Al and 60Fe in the Galaxy are studied with INTEGRAL/SPI. Both two lines are broadened slightly. The flux ratio of 60Fe to 26Al is 0.15. 26Al line energy shifts along Galactic longitudes are detected, which is consistent with expectation from Galactic rotation. 26Al emission signal toward high latitudes is detected, which would originate from local star-formation regions in the Gould Belt. Finally, 26Al spectra for three nearby star-formation regions, Cygnus, Vela and Sco-Cen, are obtained with SPI.

Relativistic calculation of Kα hypersatellite line energies and transition probabilities for selected atoms with 12 ⩽ Z ⩽ 80

The transition probabilities of Kα hypersatellite lines and energy shifts with respect to the corresponding diagram lines are computed using the Dirac–Fock model for several values of atomic number Z throughout the periodic table. The influence of the Breit interaction on the Kα1h/Kα2h line intensity ratio, Kα1h and Kα2h line energy shifts and Kα1h to Kα2h line energy splitting is evaluated. Double-K shell hole threshold values for selected elements with 23 ⩽Z⩽ 30, calculated within the same approach, are compared with available experimental results.

Post-collision effects in the beam direction in fast ion-atom collisions

Auger line shifts induced by post-collision interaction are studied for proton-atom (argon, neon) collisions. The energy shift is determined for Auger electrons emitted in the beam direction, in the Auger electron-projectile matching velocity region, for several acceptance angles for electron detection. For projectile velocities above the matching velocity, the Auger line energy shifts determined by the experiment agree with the values calculated by the existing theories, while for projectile velocities below the matching velocity, the measured and the calculated energy shifts show unambiguous disagreement. The advantage of the present work is the achievement of very small acceptance angles for electron detection (±0.2°, ±0.3°). For these acceptance angles, in the case when the projectile is slower than the Auger electron, the determined energy shift is negative, which is reported for the first time for fast-ion-atom collision processes.

L-shell ionization of Cd, Sb, Te, Ba, La, Eu, Tb and Yb by 16O ions in the energy range from 0.19 to 0.75 MeV u−1

Lα1,2, Lβ1,3,4, Lβ2,15, Lγ1(5) and Lγ2,3(4,4′) X-ray production cross-sections have been measured on selected medium-Z elements using 16O ions with energies from 0.19 to 0.75 MeV u−1. Calculated L-subshell ionization cross-sections were compared with the predictions of the direct ionization theories: the ECPSSR theory, the semiclassical approximation (SCA) in the united atom limit (SCA-UA) and SCA coupled-channel calculations (SCA-CC) involving a few lowest lying states. For the ECPSSR theory, large discrepancies were found for all three subshells. Better overall agreement between the experiment and theory was found for the SCA-UA theory. SCA-CC calculations improved the agreement between experiment and theory for the L2-subshell in the very adiabatic region. By measuring the Lα X-ray production cross-sections on W targets of different thickness, possible contribution of electron capture (EC) to the X-ray production cross-section was estimated to be less than 20%. The degree of multiple ionization of outer shells caused by heavy ion bombardment was estimated from the X-ray line energy shifts and by comparing the X-ray intensity ratios for heavy ions and protons.

Vanadium speciation by EDXRF

Elemental chemical speciation by measuring x-ray energy shifts has been carried out by various authors in the past, using tube excitation and wavelength detection. Among the most intense determined shifts are those of vanadium compounds; further, vanadium speciation determination seems to be even more important than total element analysis. In this work, the possibility of vanadium compound speciation by measuring K x-ray line energy shifts was studied by using radioactive source excitation and detection by an energy-dispersive Si(Li) detector of moderate resolution. The effect of the fitting parameters to the results was examined for the K–L2,3 and K–M2,3 lines, and the results are compared with previous data obtained by wavelength-dispersive x-ray fluorescence. © 1998 John Wiley & Sons, Ltd.

Vanadium speciation by EDXRF

Elemental chemical speciation by measuring x-ray energy shifts has been carried out by various authors in the past, using tube excitation and wavelength detection. Among the most intense determined shifts are those of vanadium compounds; further, vanadium speciation determination seems to be even more important than total element analysis. In this work, the possibility of vanadium compound speciation by measuring K x-ray line energy shifts was studied by using radioactive source excitation and detection by an energy-dispersive Si(Li) detector of moderate resolution. The effect of the fitting parameters to the results was examined for the K–L2,3 and K–M2,3 lines, and the results are compared with previous data obtained by wavelength-dispersive x-ray fluorescence. © 1998 John Wiley & Sons, Ltd.

The role of prompt electrons in the post-collision effect in fast ion - atom collisions

The influence of the post-collision Coulomb effect of direct-electrons on the Auger-line energy shift has been studied in fast proton - atom collisions. KLL and LMM Auger spectra of neon and krypton target have been measured and analysed with high precision. The semiclassical theory of the post-collision interaction (PCI) has been extended to include the effect of both the receeding projectile ion and the ejected prompt electron. Experimental and theoretical line-energy shifts exhibit a reasonable agreement in the entire angular range of the Auger emission. In a narrow cone around , the line-energy shift is influenced mainly by the PCI with the projectile ion, while at backward angles, it is predominantly governed by the ejected electron - Auger - electron interaction.

L-shell ionization of selected medium-Zelements by 0.22–0.83-MeV u−1carbon ions

Individual $L$-shell x-ray production cross sections were measured with ${}^{12}$C ions in the energy range 0.22-- 0.83 MeV u${}^{\ensuremath{-}1}$ on Cd, In, Sb, Te, Ba, Tb, and Yb targets. From these measurements the $L$-subshell ionization cross sections were extracted and compared with the predictions of the direct ionization theories, i.e., with perturbed stationary state theory with energy loss, Coulomb deflection and relativistic corrections, the semiclassical approximation (SCA) in the united-atom limit, and SCA coupled-channel calculations involving a few lowest lying states. Better overall agreement between experiment and theory was found for the SCA theory. Inclusion of the SCA coupled-channel calculations improved the agreement for the ${L}_{2}$-subshell in the very adiabatic region, but theory fails to describe ${L}_{1}$-ionization cross sections, especially in the 0.4 $<{\ensuremath{\xi}}_{{L}_{1}}<$ 0.7 region. The degree of multiple ionization of outer shells caused by C ion bombardment was estimated from the x-ray line energy shifts and by comparing the x-ray intensity ratios for carbon ions and protons.

Energy shift effect of exciting gamma line on perturbed angular distribution of resonantly scattered photons

The effect of the exciting gamma line energy shift on the resonant scattering of 129.4 FeV gamma rays of Ir-191 was observed. It was found that the rotation angle of the nuclear precession in the magnetic field depended on this shift. It manifested as a variation with the scattering angle of the shape of the carve, which describes the scattered photon intensity as a function of the shift.

Effect of theΣ(1460)on the analysis of kaonic-hydrogen x-ray deexcitation

The effect of a new $\ensuremath{\Sigma}$ state on the $2p\ensuremath{-}1s$ transition in kaonic hydrogen is discussed. It is shown that the new state can only account for a small fraction of the effect one observes in the line energy shift. This negative result provides indirect support for the need of some more sophisticated treatment of the Coulomb corrections in ${K}^{\ensuremath{-}}p$ scattering.

Inner-shell ionization created by fluorine ions in nearly symmetric collisions

We have measured projectile and target X-ray cross sections for F + Si, S, Ar and Kr collisions at projectile energies from 1 to 25 MeV. The experiments were performed under single collision conditions using a differentially pumped gas target. X-rays were measured by a Si(Li) detector and a proportional counter. The experimental cross sections are compared to predictions of theoretical models for direct and quasi-molecular ionization. Effects of multiple ionization that influence theK-shell fluorescence yields were examined using experimental information from line energy shifts and intensity ratios.

Anomalous auger shifts in chemisorption on tungsten

Substrate Auger line energy shifts for monolayer gas adsorption are readily detected. The observed shifts in tungsten are incompatible with predicted chemical-shift trends and hence relaxation effects must be considered. It is proposed that transition-metal s electrons play a decisive role in core-hole screening. The measurement of substrate Auger line energy shifts on gas adsorption may thus provide information on the contribution of these electrons to chemisorption.