Hydrogen-like Spectra Research Articles

Progress of x-ray imaging crystal spectrometer utilizing double crystal assembly on KSTAR.

The x-ray imaging crystal spectrometer (XICS) for Korea Superconducting Tokamak Advanced Research (KSTAR) has been upgraded to increase its performance including measurement capabilities and stable operation. A dual crystal assembly for simultaneous measurements of the helium-like and hydrogen-like Ar spectra is successfully installed for improving measurement capabilities. Using a safety viewing port with an illuminator and removing the XICS control system from the harsh KSTAR tokamak hall for a stable operation are newly performed. The experimental results from the improved XICS are investigated.

Magneto-excitons in Cu2O: theoretical model from weak to high magnetic fields

Recent experimental and theoretical work on hydrogen-like absorption spectra of excitons in external magnetic fields revealed new effects when the Coulomb interaction becomes comparable to the magnetic perturbation. We present a theoretical approach that allows for calculation of absorption spectra for any value of magnetic field. This approach opens the possibility to compute the optical functions i.e. reflectivity, transmission and absorption including the excitonic effects for various strength of external magnetic field.

Development of wavelength calibration techniques for high-resolution x-ray imaging crystal spectrometers on the EAST tokamak.

Newly developed large-area pixelated two-dimensional detector and two-crystal assemblies were deployed for the first time on tokamaks to enable time-resolved Bragg-diffracted x-ray imaging with good framing rate and water-cooling capabilities for in-vacuum long-pulse operations. High-quality helium-like (He-like) and hydrogen-like (H-like) argon spectra have been observed simultaneously for the first time on a single detector for a wide range of plasma parameters to infer both ion temperature and rotation profiles and support studies on spontaneous rotation, impurity transport, and RF physics. Since tokamak plasmas rotate in both the poloidal (θ) and toroidal (ϕ) directions, a reliable wavelength calibration is needed to account for the correct Doppler shift as well as to compute the spectrometer's instrumental function. Lyα lines emitted from Cd x-ray tubes are proposed to be used as "markers" to provide an in situ calibration of the EAST's X-ray imaging crystal spectrometer systems measuring He- and H-like argon spectra. The first lab test indicated that the X-ray tube can excite strong Lyα lines at 15 kV voltage and 1 mA current when the crystal is shined for 10 min. Other indirect calibration methods using locked-mode discharge scenarios were also studied as complementary methods.

Measurement of helium-like and hydrogen-like argon spectra using double-crystal X-ray spectrometers on EAST.

A two-crystal assembly was deployed on the tangential X-ray crystal spectrometer to measure both helium-like and hydrogen-like spectra on EAST. High-quality helium-like and hydrogen-like spectra were observed simultaneously for the first time on one detector for a wide range of plasma parameters. Profiles of line-integrated core ion temperatures inferred from two spectra were consistent. Since tungsten was adopted as the upper divertor material, one tungsten line (W XLIV at 4.017 Å) on the short-wavelength side of the Lyman-α line (Lα1) was identified for typical USN discharges, which was diffracted by a He-like crystal (2d = 4.913 Å). Another possible Fe XXV line (1.85 Å) was observed to be located on the long-wavelength side of resonance line (w), which was diffracted from a H-like crystal (2d = 4.5622 Å) on the second order. Be-like argon lines were also observable that fill the detector space between the He-like and H-like spectra.

Calculations of hyperfine splitting constants taking into account the volume distribution of the nuclear magnetic moment. I. Computational procedure as applied to hydrogen-like ions

A computational algorithm is developed for the magnetic-dipole constant of the hyperfine structure of atomic spectra, which takes into account the distribution of the magnetic moment in the nuclear volume both in the relativistic and in the nonrelativistic formulation. A significant difference between the nonrelativistic approximation, and the pointlike nucleus approximation is the presence of a nonzero contact hyperfine interaction for electrons with nonzero orbital angular momentum in the former case. The procedure is tested in the computation of the Bohr-Weisskopf correction for hydrogen-like spectra.

Parametrization of the Zeeman effect for hydrogen-like spectra in high-temperature plasmas

We present a method for parametrizing the Zeeman effect in hydrogen-like systems in high-temperature plasmas, where the fine-structure is completely unresolved. The method is based on the observation that the different polarization components behave collectively like separate entities, with simple relations. The entire Zeeman pattern can then be reduced to just three components, whose dependence on the magnetic field and the temperature can be described by only three numerical parameters. This makes it possible to include the influence of the Zeeman effect directly into ion temperature diagnostic procedures with minimal increase in the required computational effort and without the need for pre-calculated correction factors. We have tabulated such parametrizations—which are accurate for a wide range of fields and temperatures, even for cases when the total line-shape is no longer Gaussian—for 44 commonly studied hydrogen-like transitions. The effects of non-statistical population distribution in the upper sub-levels are briefly discussed, and we also note a temperature-dependent wavelength shift of the centre positions of the transitions.

X-ray spectra from highly ionized dense plasmas produced by ultrashort laser pulses

Hydrogen-like and helium-like X-ray spectra (between 7.1 and 8.2 A, i.e., 1500 to 17.50 eV, respectively) from solid aluminium targets irradiated with high intensity (up to 1017 W/cm2) subpicosecond (0.7 ps) laser pulses have been measured. The spectra show that the resonance lines are very broad and very asymmetric. Evidence for a Doppler-shifted reabsorption of the resonance line emission has been found. The spectra have been simulated by a computer code for the calculation of spectral-line intensities and linewidths. Electron densities exceeding the critical density have been estimated for different laser intensities by comparing the observed and simulated intensity ratio of different dielectronic satellite lines. From the X-ray spectra generated byp- ands-polarized radiation fat different laser intensities, the thresholds for the formation of hydrogen-like and helium-like ions have been determined.

Braid group related algebras, their representations and generalized hydrogenlike spectra

Representations of the n-braid group where generators are given by matrices whose elements belong to a noncommutative algebra are discussed. Representation of this algebra in a Hilbert space generalizes the Burau representation. Two algebras which are closely related and are physically indistinguishable provided that a particular eigenvalue is fine tuned are discussed. It is shown that the generalized oscillator system given by one of the algebras generates a hydrogenlike spectrum.

Observation of hydrogenlike and heliumlike krypton spectra

Hydrogenlike and heliumliken=2→n=1 lines in Kr have been produced and studied for the first time. HydrogenlikeL y α lines have been observed and the fine structure interval has been determined. The absolute energy of the1P1,3P2,3P1 lines of heliumlike Kr have been measured and compared to Multiconfigurational Dirac-Fock Calculations.

Early Observations of Highly Charged Ions

This paper gives an outline of the development of extreme ultraviolet spectroscopy with special emphasis on the phase that began in 1929 when a grazing-incidence spectrograph had been designed by Manne Siegbahn and was put in use at Uppsala. Among the initial results we note the recording of the resonance lines of helium- and hydrogen-like spectra of some light elements down to 40 Å. A second decisive step is then marked by taking in use in 1935 a 5 times larger spectrograph of the same type, also designed by Siegbahn. The speed and high resolving power of the new instrument opened up the region below about 200 Å for studies of the complex spectra of the heavier elements. Combined with a vacuum spark of optimized ionizing power it made possible the discovery of sodium-like spectra up to Cu XIX and of copper-like spectra to Sb XXIII as well as the resonance lines in the cobalt sequence up to Sn XXIV. Among the analyses achieved in this period we mention in particular those of Fe X and Fe XI which were to give the first clue to the interpretation of the spectrum of the solar corona.

Imploding argon plasma experiments

The Pithon pulsed electron beam accelerator was used to implode an argon plasma at 4 TW. The plasma was prepared by microwave preionization of an annular column of gas injected between the output electrodes of the pulser. The electrodynamic behavior implied that most of the gas was involved in the pinch. The plasma conditions were inferred from hydrogenlike and heliumlike x-ray emission spectra. Final pinch dimensions were determined from x-ray pinhole photographs and laser shadowgraphs.

Variational approach to bound states in scalar-gluon field theory

Two variational approaches are employed to attack the bound-state problem of a charged scalar field interacting with an Abelian gauge field. The resulting variational equations allow for a qualitative discussion of all possible physical situations. Boundary conditions play a crucial role in their interpretation. A specially developed perturbation scheme yields hydrogenlike spectra. "Self-trapping" solutions and configurations with complete screening of the long-range force are discussed and are shown not to be obtainable by perturbation for small coupling. Metastable states appear for strong coupling.

The Doublet Riddle and Atomic Physics circa 1924

* University of Rochester. original version of this paper was read at the annual meeting of the History of Science Society in San Francisco, 29 December 1965. A subsequent version was awarded the 1966 Henry Schuman Prize. For criticism and advice I am indebted to Jack Felman, John L. Heilbron, Martin J. Klein, and Thomas S. Kuhn; in particular, I profited from the text of a talk on The Crisis of the Old Quantum Theory, 1922-1925 given by Prof. Kuhn at the American Philosophical Society in April 1966. developments discussed in the present paper are touched upon in a number of recent retrospective accounts. R. Kronig, The Turning Point, in Theoretical Physics in the Twentieth Century, ed. M. Fierz and V. F. Weisskopf (New York: Wiley, 1960), pp. 539; F. Hund, G6ttingen, Kopenhagen, Leipzig im Riickblick, in Werner Heisenberg und die Physik unserer Zeit, ed. F. Bopp (Braunschweig: Vieweg, 1961), pp. 1-7; S. Goudsmit, Entdeckung des Elektronspins (Max-Planck-Medaille lecture), Physikalische Bliitter, 1965, 21 :445-453. 1 G. E. Uhlenbeck and S. Goudsmit, Ersetzung der Hypothese vom unmechanischen Zwang durch eine Forderung beziglich des inneren Verhaltens jedes einzelnen Elektrons, Die Naturwissenschaften, 1925, 13:953-954 (published 20 Nov. 1925; dated 17 Oct. 1925). 2 spectral lines (whether in the optical or X-ray region) emitted by an atom of a given element are described as possessing a series and a fine, or complex, or structure; the same is said of the energy levels, or spectroscopic terms, which characterize the stationary states of the atomthe spectral lines being emitted in transitions between stationary states. Series structure and structure refer quite directly to characteristic patterns on a spectrogram, i.e., a series of relatively widely separated lines, each such line being in fact often composed of several closely spaced components, constituting the fine (or complex) of the line. simplest of the omplex structures, both in the X-ray and the optical spectra, is the doublet, a closely spaced pair of spectral lines. Doublets, for example, are characteristic of the of the optical spectra of the alkali metals. By 1922 the term structure was rather carefully restricted to the X-ray spectra and to the optical spectra of atoms with but one electron, while the term complex structure was applied particularly to the optical spectra of atoms with more than one electron, but was also used generically. By 1924 the burden of the particular reference had largely been assumed by the term multiplet structure, while complex structure for a time held on as the generic term for groups of lines which, considered as units, formed a series. Until mid-1924 it was generally accepted that the use of the two expressions (series and complex, or fine, structure) in connection with both the optical spectra of higher atoms, on the one hand, and the X-ray and hydrogen-like spectra on the other hand, merely reflected superficial similarities of the patterns on the spectrograms. alteration of this view, and the consequent difficulties for the Bohr theory, are described below.

Infinite-Component Wave Equations with Hydrogenlike Mass Spectra

Continuing a previous work, various models of relativistic wave equations are considered which have an infinite number of components. By combining a unitary representation of $SO(4, 2)$ and the ordinary finite (Dirac) representation of the Lorentz group, it is possible to construct equations which produce hydrogenlike mass spectra. However, they are also accompanied by redundant, or unphysical, solutions. In the nonrelativistic limit, on the other hand, the equations obtained can be shown to be mathematically equivalent to the Schr\"odinger equation for the hydrogen atom. This suggests that the method of infinite-component wave equations may be a useful tool in exploring the physics of strong interactions. A general discussion is made about the principles and problems that will be relevant in pursuing such a program.

Measurement of Absolute Radiation Intensities in the Vacuum-Ultraviolet Region

A method for calibrating vacuum-ultraviolet monochromators for measurement of absolute radiation intensities is described. It is based on calculating the brightness of an optically thin spectral line in the far ultraviolet from the brightness of a visible line originating from the same upper level. A grazing incidence monochromator and a Seya–Namioka monochromator were calibrated at a number of wavelengths between 1640 and 231 A, using line pairs of hydrogen and ionized helium. Light sources used to obtain these lines are described. Problems of measurement and sources of error, particularly in the case of hydrogenlike spectra, are discussed.

Review of the experimental evidence for the law of variation of the electron mass with velocity

The paper reviews the actual experiments in which the dependence of electron mass on velocity is investigated. It is found that the most precise verification of the relativistic formula follows from the fine structure doublet separation of hydrogen-like spectra. Regarding the direct experiments on the behaviour of free electrons, the results do not contradict the relativistic formula, although the experimental error of the available measurements is rather high; i.e. it is in most cases comparable with the difference between theoretical formulae derived from different assumptions. Recent measurements on the velocity dependence of the mass of protons are also reviewed.

Hydrogen-like absorption spectra due to excitons in cadmium sulphide single crystals (Summary)

Hydrogen-like absorption spectra due to excitons in cadmium sulphide single crystals (Summary)

The Stark effect in hydrogen-like spectra

The theory is extended to the case in which levels with the same n and j are not degenerate. A formula is given for a Stark effect which is small compared with the separation between n S ½ and n P ½ .

Fine Structure of the He II Line λ = 4686 A.

ACCORDING to the Dirac theory of the energy states in hydrogen-like spectra, levels of the same principal quantum number n which have the same value of the quantum number of total angular momentum j should coincide. Lamb and Retherford1 have shown that in the second quantum state of the hydrogen atom the 2 2S1/2-level lies 0·03 cm.-1 above the 2 2P1/2, term. Bethe2 has tried to explain this discrepancy by an interaction of the electron with the radiation field. His preliminary calculations show complete agreement with experiment for the hydrogen atom. For the He II spectrum he predicts a shift of the 3 2S1/2-level with respect to the 3 2P1/2-level by 0·13 cm.-1.

Hydrogen-like Spectra of Lithium and Beryllium in the Extreme Ultra-violet

IN preceding communications (NATURE, NOV. 2, 1929, and Comptes rendus, Jan. 1930) we have given a brief account of the extension of the extreme ultraviolet down to 100 resp. 88 A. in the spectrum of doubly ionised beryllium (Be III). Using a vacuum-spark with a considerably increased capacity and ionisation power, it has now been possible to record the strongest radiations in the hydrogen-like spectra of completely ionised lithium (Li III) and beryllium (Be IV), thus extending optical spectra to 76 A.