Ion Beam Spectroscopy Research Articles

Low-energy state-selective charge transfer by multiply charged ions.

We present a combined rf-guided ion beam and photon emission spectroscopy method, which facilitates state-selective charge-transfer measurements at energies of direct relevance for astrophysics and fusion-plasma diagnostics and modeling. Ion energies have been varied from 1000 eV/amu down to energies as low as 5 eV/amu. Absolute state-selective cross sections have been obtained for He (2+) and N (5+) ions colliding on molecular hydrogen. Orders of magnitude differences are found between theory and the present results. This indicates clearly that such data are valuable as benchmarks for the necessary advancement of theoretical descriptions.

Characterization of transmission-type curved-crystal X-ray optics for fast ion-beam spectroscopy

The behavior of curved-crystal X-ray spectrometers in combination with fast moving sources is studied. A three-dimensional Monte-Carlo ray-tracing calculation is presented for cylindrically bent crystals used in transmission. The method allows an accurate calculation of two-dimensional line shapes and of geometrical aberrations. The geometrical formulae derived can be used for the design of spectrometers and for the analysis of experiments. For some limiting cases analytical expressions for the X-ray images are given and compared with the numerical calculations.

Characterization of 3C-SiC films grown on monocrystalline Si by reactive hydrogen plasma sputtering

Detailed characterization using x-ray diffractometry, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and Auger infrared and focused ion-beam spectroscopy, was carried out on cubic SiC films grown on single-crystal (100) Si substrates by reactive hydrogen plasma sputtering over a range of growth temperatures between 700 and 1000 °C. It was found that the first few deposited atomic layers were always amorphous. The subsequent SiC films showed well-defined (111) growth at the lowest temperatures, becoming randomly oriented by 1000 °C. The measured C:Si ratio was always >1, and varied with depth inside a film and also with temperature. At higher temperatures, the presence of “hollow voids” was observed, our data being consistent with their formation by outdiffusion of Si atoms from the substrate through the SiC layer. Associated with the hollow voids we observed the presence of a porous, highly C-rich region at the Si–SiC interface. We propose that this was due to diffusion of C from the SiC film into the voids themselves.

Isotope shifts of optical transitions in Ce II by collinear laser - ion-beam spectroscopy

Isotope shifts of seven optical transitions ( - 590.0 nm) in Ce II for stable isotopes have been measured by collinear laser - ion-beam spectroscopy. As an absolute frequency reference, polarization spectroscopy of was employed. The field shifts and the specific mass shifts were deduced from observed isotope shifts through the King-plot analysis for all spectral lines. The changes of mean-square charge radii for stable isotopes were determined from the field shifts. The results obtained and those of the previous works were in good agreement. According to the sharing rule, composition of the levels concerning this measurement was evaluated from the isotope shifts.

Atomic, molecular, & optical physics handbook

Partial Contents: Units and Constants. Mathematical Methods. Angular Momentum Theory. Group Theory for Atomic Shells. Dynamical Groups. Computational Techniques. Hydrogenic Wave Functions. Atoms. Atomic Spectroscopy. High Precision Calculations for Helium. Atomic Multipoles. Atoms in Strong Fields. Ion Beam Spectroscopy. Thomas- Fermi and Other Density-Functional Theories. Many-Body Theory of Atomic Structure and Processes. Photoionization of Atoms. Quantum Electrodynamics. Tests of Fundamental Physics. Parity Nonconserving Effects in Atoms Molecules. Molecular Structure. Radiative Transition Probabilities. Molecular Photodissociation. Time-Resolved Molecular Dynamics. Gas Phase Ionic Reactions. Clusters. Infrared Spectroscopy. Laser Spectroscopy in the Submillimeter and Far-Infrared Region. Spectroscopic Techniques: Lasers. Spectroscopic Techniques: Ultraviolet. Scattering Theory. Elastic Scattering: Classical, Quantal and Semiclassical. Orientation and Alignment in Atomic and Molecular Collisions. Positron Collisions. Adiabatic and Diabatic Collision Processes at Low Energies. Ion Atom Charge Transfer Reactions at Low Energies. Continuum Distorted Wave and Wannier Methods. Dielectronic

Hyperfine structure investigations and identification of new energy levels in the ionic spectrum of 147Pm

Hyperfine structure splittings have been measured for 75 lines of singly ionized promethium 147Pm II with a hollow cathode discharge and a Fabry-Perot interferometer. Magnetic dipole and electric quadrupole splitting factors A and B have been determined for 10 levels of the 4f56s configuration, 2 levels of 4f55d, and 57 upper undesignated levels. The A-factors are in general agreement with calculated values. With the aid of Hartree-Fock calculations and Zeeman-effect data, four new levels of the 4f5(6H)5d 7K term were located. The strong lines terminating on these 7K levels originate from levels of 4f5(6H)6p7I, which were already known, but had not been designated. An unidentified line at 556.17 nm previously observed with collinear laser ion-beam spectroscopy is now classified as 4f5(6H)5d7K6-4f5(6H)6P7I5.

Partial and total cross sections for single electron capture by Ar8+ from He in the 400-2400 eV energy range

Charge-exchange processes in 400-2400 eV Ar8+-He collisions are investigated: high energy resolution ion beam spectroscopy is performed with a recoil ion source (RIS) built in GANIL, total and partial cross sections for single-electron capture are measured using retarding field and energy gain techniques. Comparison with previous experimental results for total charge-exchange cross sections shows a rather good agreement and confirms the independence of these cross sections on the collision energy in the studied range. In contrast partial charge-exchange cross sections are shown to depend strongly on the collision energy. The experimental data are compared with theoretical results in the semi-classical impact parameter frame and with predictions made by other authors using the Landau-Zener model.

J-dependence of optical isotope shifts in Sm II

Isotope shift measurements in 18 optical transitions between 8 samarium isotopes ASm have been taken (A=144, 146, 147, 148, 149, 150, 152, 154) using collinear laser ion beam spectroscopy. For the even-A isotopes, a direct-measurement technique was developed. A multidimensional King plot served to evaluate the term-related isotope shifts in the fine-structure multiplet 4f6(7F)5d8HJ. These shifts should show a linear dependence on J(J+1) in accordance with a crossed second-order approximation. A closer correlation is found between the isotope shifts and the fine-structure energies. Field shift and mass shift can be separated in order to calculate changes of mean-square charge radii delta (r2).

Ion-beam spectroscopy of long-range complexes

Ion-beam techniques provide opportunities for extremely sensitive spectroscopic studies of molecular ions. Transitions involving the energy levels lying close to the dissociation limit may be detected through a range of indirect methods; electric field dissociation has proved to be particularly valuable. This review describes IR and microwave studies of a range of molecular ions, mostly diatomic; we compare the different detection methods and the molecular information each provides. These investigations have revealed the first electronic spectra of the H2+ and D2+ ions, leading to detailed characterisations of the long-range H⋯H+ and D⋯D+ charge–induced-dipole states, and also providing accurate data with which to test ab initio calculations. In the case of the HD+ ion the high spectroscopic resolution achieved enabled the nuclear hyperfine interactions to be measured; these revealed marked asymmetry in the electron distribution as the dissociation asymptote is approached. H3+, the only polyatomic molecule to be investigated in our laboratory so far, exhibits an extraordinarily rich and complex IR predissociation spectrum, which arises from metastable periodic states embedded in a chaotic sea of levels lying above the lowest dissociation limit. Other examples of predissociation spectra involving rotationally quasibound levels are described. In recent work the first 37 bound levels of the long-range He⋯Ar+ complex, counting from the dissociation limit downwards, have been identified and described theoretically. In this very weakly bound region the Born–Oppenheimer approximation collapses because of extremely strong coupling between the electronic and nuclear rotational motions. Finally, we describe new experiments using a combined neutral–ion beam source which has enabled the first state-to-state resonant spectra of the Ar2+ and Ne2+ molecular ions to be observed.

Measurements of total kinetic energy released to the n=2 dissociation limit of H 2. Evidence of the dissociation of very high vibrational Rydberg states of H 2 by doubly excited states

Measurements of total kinetic energy of H 2 released to H fragments connected to the n=2 dissociation limit are presented. These results were obtained with fast ion beam and laser optical translational spectroscopy. The observed data revealed over 2.8 eV of kinetic energy and confirmed the involvement of the first Q 1 doubly excited states having the H(1s) + H( n=2) diabatic limit, in the dissociation process of high vibrational excited Rydberg states.

Excited-level lifetimes and hyperfine-structure measurements on ions using collinear laser-ion-beam spectroscopy.

The mean lifetimes \ensuremath{\tau} of the Ca ii 4p $^{2}$${\mathit{P}}_{1/2}$ and 4p $^{2}$${\mathit{P}}_{3/2}$ levels, and the $^{35}\mathrm{Cl}$ ii 4p' $^{1}$${\mathit{F}}_{3}$ level, have been measured by a variant of the collinear laser--ion-beam lifetime technique applied previously to the Ar ii 4p' $^{2}$${\mathit{F}}_{7/2}^{\mathit{o}}$ level [Jian Jin and D. A. Church, Phys. Rev. A 47, 132 (1993)]. The present results are \ensuremath{\tau}(Ca ii, 4p $^{2}$${\mathit{P}}_{1/2}$)=7.098(0.020) ns, \ensuremath{\tau}(Ca ii, 4p $^{2}$${\mathit{P}}_{3/2}$)=6.924(0.019) ns, and \ensuremath{\tau}(Cl ii, 4p' $^{1}$${\mathit{F}}_{3}$) =11.17(0.06) ns. The experimental lifetimes of these, plus the Ar ii 4p' $^{2}$${\mathit{F}}_{7/2}$ level, are compared with available recent many-electron calculations. Typically 1%--3% differences between measurement and ab initio theory are found, while certain semiempirical calculations are in better agreement with experiment. Data for other precise lifetime measurements on alkali-metal systems are compared with recent ab initio and semiempirical calculations to provide perspective on the Ca II results. The hyperfine structure of the $^{35}\mathrm{Cl}$ II 3d' $^{1}$${\mathit{G}}_{4}$--4p' $^{1}$${\mathit{F}}_{3}$ transition was also measured and analyzed in the course of the measurements, with the resulting hyperfine-structure constants: A${(}^{1}$${\mathit{F}}_{3}$)=301.9(0.5) MHz, B${(}^{1}$${\mathit{F}}_{3}$)=-6.7(0.8) MHz, A${(}^{1}$${\mathit{G}}_{4}$)=205.1(0.5) MHz, and B${(}^{1}$${\mathit{G}}_{4}$)=-3.9(2.4) MHz.

Hydrogen Effects on the Fracture of Thin Tantalum Nitride Films

AbstractIn this study we used nanoindentation and continuous microscratch testing to determine the effect of hydrogen on the work of adhesion and fracture toughness of thin tantalum nitride films. These films were sputter-deposited on sapphire substrates to a thickness of 600 nm followed by the heating of some films in deuterium and some in vacuum at 300°C. Deuterium was used in this study because it is much easier to detect and measure than hydrogen. Ion beam spectroscopy showed that exposure to deuterium produced a uniform internal deuterium concentration of 2000 appm. Nanoindentation showed that exposure to deuterium at 300°C and vacuum annealing at 300°C had little effect on elastic modulus and hardness values of these films at room temperature. In contrast, the microscratch tests at room temperature revealed that the work of adhesion decreased from 24.5 J/m2 after vacuum annealing to 9.1 J/m2 after deuterium charging and demonstrated that tantalum nitride films have a strong susceptibility to hydrogen embrittlement.

Precision lifetimes for the Ca+ 4p 2P levels: Experiment challenges theory at the 1% level.

The mean lifetimes \ensuremath{\tau} of the ${\mathrm{Ca}}^{+}$ 4p $^{2}$${\mathit{P}}_{3/2}$ and $^{2}$${\mathit{P}}_{1/2}$ levels have been measured to \ensuremath{\approxeq}0.3% precision using a variant of the collinear laser-beam\char21{}ion-beam spectroscopy technique. Like previously measured precision lifetimes of light alkali-metal-like systems, these data fall significantly higher than calculations by the most recent multiconfiguration Hartree-Fock and relativistic many-body perturbation theories. Discrepancies between experiment and theory for alkali-metal-like systems have implications for the interpretation of parity-violation research.

How accurate are the "muonic" quadrupole moments in Eu?

The electric quadrupole hyperfine structure splitting constants B of the Eu isotopes 145-147, 151-153 were measured with collinear laser ion beam spectroscopy in 17 different transitions. From 105 experimental data B values of all levels in EuII 4f 7 ( 8 S)5d 9 D J ,...6p(7/2;1/2) J , and...6p(7/2;3/2) J were determined in enhanced accuracy. The ratio 151 B/ 153 B=0.39184(22) (mean value) significantly deviates from values of muonic measurements but is in good agreement with other atomic ones in Eu I and Eu II

Hyperfine structure and isotope shift investigations of 145Pm and 147Pm

In the promethium II spectrum hyperfine structures (HFS) and isotope shifts (IS) of the two transitions 4f 5(6H)5d 7KJ=4 to 23261.30J=3 cm-1 at lambda =557.6 nm and 4f 5(6H)5d 7KJ=4 to 23761.98J=3 cm-1 at lambda =542.5 nm of the radioactive isotopes 145Pm and 147Pm have been studied by collinear laser ion beam spectroscopy. The nuclear moments for 145Pm have been deduced. A hyperfine structure anomaly could not be detected. The sign of the isotope shift confirms the 5d-6p character of the transition. The experimental data for the moments are in relatively good agreement with Hartree-Fock and Nilsson model calculations and with that of neighbouring nuclei of europium and praseodymium.

Kinematic compression and expansion of the velocity distributions of particles in gas flows.

Velocity distribution functions showing kinematic compression and expansion are derived in the context of gravitational forces. Whereas kinematic compression is well known in laser ion-beam spectroscopy, kinematic expansion is a new concept. In our analysis, collisionless and weak-collision cases are considered. A brief discussion shows that the weak-collision case may be appropriate in certain regions of the interstellar medium and that kinematic compression and expansion could have interesting observational consequences. In particular, as we show elsewhere, kinematic expansion may be important in the formation of broad and asymmetric quasistellar object emission lines.

Hyperfine structure of Sc II: Experiment and theory.

Collinear laser--ion-beam spectroscopy has been used to measure hyperfine structure (hfs) in three levels of the 3${d}^{2}$ and six levels of the 3d4p configuration of Sc ii. The results combine with earlier measurements of hfs within these configurations to give a fairly complete picture of hfs in these configurations. The combined results are compared with multiconfiguration Dirac-Fock (MCDF) ab initio calculations. Good agreement is obtained for the magnetic dipole hfs constants of the singlet states in both the 3${d}^{2}$ and 3d4p configurations, but the MCDF predictions for the triplet states are not even qualitatively correct. The poor agreement for the triplet states appears to be due to the neglect of core polarization in the present MCDF approach.

A convenient energy analyzer calibration technique

As part of a continuing program of fast ion beam spectroscopy studies and of investigation of the ion-foil interaction process, the need arose for a convenient technique for in situ calibration of an electrostatic energy analyzer. We describe here a calibration procedure based upon observation of the collisional dissociation of diatomic molecular ions in a gas cell which is biased by a precision power supply to a potential V in the range −16 to +16 kV. By measuring the apparent energy of the monatomic ions resulting from dissociation in the gas cell as a function of the applied voltage V, one can obtain the actual ion energy and the analyzer calibration factor; the undissociated ion peak then furnishes a second calibration point. This technique is particularly convenient for the energy range of the low energy heavy-ion accelerators, used here: energies less than a few hundred keV. Limitation of the precision obtained is due to the accuracy with which the center of the somewhat broad energy spectrum of the ion from molecular dissociation can be determined and, to a lesser extent, by the accuracy of the calibration of the output of the precision power supply employed.

Fine Structure of the 1s2s2p 4P0 and 1s2p2 4P Doubly Excited States of Lithiumlike Si XII

AbstractThe ls2s2p4P0- ls2p24P transitions of Si XII have been investigated using fast ion beam spectroscopy in the far ultraviolet. The results for fine structure intervals and term separation represent the highest Z test of electron correlation effects and relativistic contributions in doubly excited states of lithiumlike ions.

Collinear laser ion beam spectroscopy

Collinear Laser Ion Beam Spectroscopy (CLIBS) investigates hyperfine structures (hfs) and isotope shifts (IS) in spectral lines and is well suited for the study of nuclear moments of short-lived isotopes. It is fast, highly selective, highly sensitive and allows many experimental alternatives. The high accuracy makes it also an interesting tool for atomic physics.