Beam-foil Spectroscopy Research Articles

Efficiency and resolution characterisation of a high-resolution bent crystal X-ray spectrometer using ray-tracing simulations

We report the characterisation of the efficiency and resolution of a high-resolution bent crystal spectrometer under Johannson geometry, using ray-tracing simulations. The spectral resolution is measured experimentally from electron-beam and fast ion-beam interactions with thin solid foils. The X-rays emitted by target atoms as well as projectile ions are studied. The results of the ray-tracing simulations are in very good agreement with the beam-foil spectroscopy experiments. The geometrical factors affecting the resolution are also discussed in detail. We also characterise the detection efficiency of the spectrometer by simultaneous measurements of X-rays using a semiconductor detector, i.e. Si(Li) detector, with known detection efficiency. These results are also compared with the ray-tracing simulation results.

Atomic Lifetimes of Astrophysical Interest in Ions of Fe

Multiply charged ions of iron dominate the EUV spectrum of the solar corona. For the interpretation of such spectra, data on both the atomic structure and the transition rate are essential, most of which are provided by theory and computation. The wavelengths of observed spectra are used to test the predicted energy level structure, while the line intensities depend on level lifetimes and branch fractions. A number of electric dipole and higher-order transition rates have been measured over the years in the laboratory, mostly by beam-foil spectroscopy, at heavy-ion storage rings, and at various ion traps. In this paper, the state of the knowledge base on level lifetimes in all ions of Fe is assessed, and the problems of further progress are outlined.

EUV Beam-Foil Spectra of Titanium, Iron, Nickel, and Copper

Beam–foil spectroscopy offers the efficient excitation of the spectra of a single element as well as time-resolved observation. Extreme-ultraviolet (EUV) beam–foil survey and detail spectra of Ti, Fe, Ni, and Cu are presented, as well as survey spectra of Fe and Ni obtained at an electron beam ion trap. Various details are discussed in the context of line intensity ratios, yrast transitions, prompt and delayed spectra, and intercombination transitions.

Employing X-ray absorption technique for better detector resolution and measurement of low cross-section events

Abstract The versatility of X-ray absorption technique is experimentally employed for enhancing the detector resolution and to rejuvenate the low probable transitions obscured in the pile-up region, during a beam-foil spectroscopy experiment. The multiple aluminum absorber layers (10 μm each) are used to suppress the pile-up contribution drastically and to restore a weak transition which is about 1.38 × 104 times weaker than a one-electron-one-photon transitions viz. Kα and Khα. The weak line is possibly originating from a two-electron-one-photon transition in He-like Ti. Further, the transitions, which were obscured in the spectra due to high intensity ratio, are revived by dissimilar line intensity attenuation using this technique. The measured lifetimes of Kα line with and without intensity attenuation match well within error bar. The present technique finds potential implications in understanding the structure of multiple-core-vacant ions and other low cross section processes in ion-solid collisions.

Development of a multipurpose beam foil spectroscopy set-up for the low cross-section measurements

A multipurpose facility for low cross section measurements has been developed at Inter University Accelerator Centre, New Delhi, India. The facility consists of a multipurpose miniature chamber equipped with 1m focal length normal incidence Monochromator and charge coupled device based detection system which has been aligned to realize the best resolution of the spectrometer. The chamber in this facility collects radiation 100 times more efficiently from the older system, without using any extra focusing mirror assembly. It is ensured to have the provision of mounting an X-ray detector and the spectrometer transverse to the beam direction simultaneously in the same chamber. The atomic spectroscopic studies can be performed by interaction of ions beams with both thin foil and gas targets. Provision for using photomultiplier tube instead of charge coupled device, is employed in the system depending on the condition of the source strength or other detection issues. We observed the essence of a very weak atomic phenomenon, a triply excited autoionizing forbidden transition, using the above facility to demonstrate its capability for measuring such low cross section phenomena. The present developed facility covers a large spectroscopic region from X-rays to the near infrared (0.1–10,000Å).

Effect of cascade through circular Rydberg states and surface wakefield on the decay of n=2→n=1 transition of H-like V in beam–foil excitation

Beam–foil spectroscopy is used to study the unresolved decay of short-lived 2p (τ2p≈5.3fs) and long-lived 2s (τ2s≈756.7ps) states of H-like V for the time range 25–400ps. We have observed a hump-like structure, peaked at ~145ps, in the decay of the 2p state riding on the decay curve of the 2s state. This unusual behavior is similar to the one reported by us recently in H-like Fe (Mishra AP, et al. J Quant Spectrosc Radiat Transfer 2013;120:114–9) and occurs as a consequence of the sequential cascading down of circular Rydberg states to the 2p state. More importantly, it is inferred in this paper that Nandi and Mohanty (Nandi T, Mohanty BP. J Phys B: At Mol Opt Phys 2009;42:225402), who attributed the drastic reduction in the observed lifetime of the 2s state in beam-foil excitation to Stark mixing of the 2s2S1/2 and 2p2P1/20 states due to the wakefield at the exit surface of the foil, had overestimated the Stark mixing parameter and the strength of the wake electric field responsible for the mixing at least by a factor ~5.5.

Observation of transitions involving core-excited states in Ar III and Ar IV and high-lying singly excited states in Ar I–Ar IV

In this paper we present a comprehensive analysis of beam-foil and beam-gas excited spectrum of argon observed in small wavelength region, 2965–3090 Å, using Ar +/2+ ions in the energy range 200–650 keV. The comparison of beam-foil spectrum (BFS) at different incident beam energy and with that of beam-gas spectrum (BGS), one can find solution for blending problem in beam-foil spectroscopy. Many new transitions were identified on the basis of calculated wavelength from the accurately known energy levels of Ar I, Ar II, Ar III and Ar V. The transitions of Ar I originate from highly excited states (10 p to 17 p and 10 f to 17 f). Based on TOPbase estimates using close-coupling approximation five transitions involving core-excited states and nine transitions originating from highly excited states in the spectrum of Ar III and Ar IV were also identified. Radiative life time of two core excited quintet states (3 s3 p 4( 4P)6d 5D and 3 s3 p 4( 4P)8 f 5F o) of Ar III were measured and found to be in ‘good’ agreement with that of the calculated value using close-coupling approximation.

Indrek Martinson

Indrek Martinson, an internationally recognized expert on accelerator-based atomic physics, died unexpectedly but peacefully in Södra Sandby, Sweden, on 14 November 2009. Indrek was an emeritus professor at the University of Lund in Sweden and director of the university’s department of atomic spectroscopy; he also was a former chair of the physics section of the Royal Swedish Academy of Sciences, which oversees the awarding of the Nobel Prize in Physics.Indrek was born on 26 December 1937 in Tartu, Estonia. Although it had been independent since 1918, during World War II Estonia was occupied by the Soviet Union, then by Germany, and then again by the Soviet Union. With the second Soviet occupation in 1944, Indrek and his family were forced to leave their home and become refugees in Germany. Two years later the Martinsons immigrated to Sweden, where Indrek obtained citizenship.Indrek’s first research studies began in 1961 and were in beta- and gammaray spectroscopy, carried out under Manne Siegbahn at the Nobel Institute for Physics in Stockholm. In 1964 Indrek, Torsten Alväger, and Hans Ryde performed a measurement that set a lower limit for the lifetime of the proton. The measurement subsequently provided a test of weak-interaction theories. In 1968, at the suggestion of institute director Ingmar Bergström, Indrek began studies in time-resolved fast-ion-beam spectroscopy. Those methods were being developed at the University of Arizona by Stanley Bashkin and William Bickel, and Indrek spent one year as a visiting scientist there.After a productive year abroad, Indrek returned to Stockholm, and together with Jan Bromander and Gordon Berry arranged the Second International Conference on Beam-Foil Spectroscopy, held in June 1970 in Lysekil on the west coast of Sweden. The conference marked a great expansion of the field of accelerator-based atomic physics, with many active laboratories reporting new results. By then, lifetime studies were complemented by fine- and hyperfine-structure measurements using coherent-excitation and quantum-beat methods. Siegbahn, retired but still active at the Nobel Institute, was intrigued by the possibilities of atomic structure studies using accelerators, and each month Indrek and Siegbahn met to discuss the latest results. In 1971 Indrek completed his filosofie doktor thesis titled “Investigations of Atomic Spectra and Transition Probabilities Using Beam-Foil Excitation.”In 1976 Bengt Edlén’s retirement from the University of Lund left vacant the professorship once held by Janne Rydberg. In a highly selective competition, Indrek was chosen to occupy that chair and lead the university’s department of atomic spectroscopy. Rather than completely reorganizing the department, Indrek established a synergy between the high-wavelength- resolution spectroscopy of Edlén and his own time-resolved measurements. He also introduced laser- and tokamak-produced plasma light sources, synchrotron- radiation measurements, and Fourier transform spectroscopy. He pioneered the measurement of lifetimes of multiply excited states, developed a method that combines quantum-beat and lifetime measurements to obtain unprecedented accuracies in half-lives and fine-structure splittings, and devised an ingenious method for measuring forbidden transition rates through differential lifetime measurements. Many of his halflife measurements have altered accepted elemental solar and stellar abundances. Indrek created an atmosphere of international collaboration that brought together many individuals and techniques. He opened exchanges between scientists in the West and those in Estonia, Lithuania, Russia, China, and Japan. A touching moment occurred in 1991, when Indrek returned to the city of his birth to receive an honorary doctorate from the University of Tartu. He was awarded Estonia’s Order of the White Star in 2001 for service to the country.Indrek’s life was rich and varied. In addition to his abilities as a physicist, he had a great love for classical music and sports and a vast knowledge of both. A top-ranked chess player in Stockholm, Indrek often entertained visiting international chess masters and was able to hold Bobby Fischer to a draw.Indrek was a gifted and imaginative scientist, a great humanitarian, and one of the kindest and most personable people that I have known.Indrek MartinsonPPT|High resolution© 2010 American Institute of Physics.

Atomic structure calculations and beam-foil observations of La IV

Relativistic Hartree–Fock and multiconfigurational Dirac–Fock calculations of atomic structure and transition rates have been carried out in trebly ionized lanthanum (La3+, Z = 57). The calculations have to cope with configuration interaction effects but also with the very complex situation of the collapse of the 4f wave function. The calculations are compared to experimental data obtained with beam-foil spectroscopy in the extreme ultraviolet, at ion energies that favour the production of the spectrum La IV. Besides lines known from sliding spark discharges, many more lines are observed that have not yet been identified. Time-resolved measurements yield three level lifetimes in La IV that agree roughly with the results of our own calculations.

Hydrogenic Lamb shift inGe31+and the fine-structure Lamb shift

Using x-ray diffraction and beam-foil spectroscopy, we have determined precise wavelengths for Lyman ${\ensuremath{\alpha}}_{1}$ and Lyman ${\ensuremath{\alpha}}_{2}$ in hydrogenic germanium of $1.166\phantom{\rule{0.2em}{0ex}}993\phantom{\rule{0.2em}{0ex}}8\ifmmode\pm\else\textpm\fi{}33\ifmmode\pm\else\textpm\fi{}169$ and $1.172\phantom{\rule{0.2em}{0ex}}433\phantom{\rule{0.2em}{0ex}}6\ifmmode\pm\else\textpm\fi{}39\ifmmode\pm\else\textpm\fi{}170\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. Hydrogenic germanium ${\mathrm{Ge}}^{31+}$ $1s\text{\ensuremath{-}}2{p}_{3∕2}$ and $1s\text{\ensuremath{-}}2{p}_{1∕2}$ Lamb shifts are measured to be $66\phantom{\rule{0.2em}{0ex}}080\ifmmode\pm\else\textpm\fi{}237\ifmmode\pm\else\textpm\fi{}1121$ and $67\phantom{\rule{0.2em}{0ex}}169\ifmmode\pm\else\textpm\fi{}281\ifmmode\pm\else\textpm\fi{}1237\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, respectively. This $14\phantom{\rule{0.3em}{0ex}}\mathrm{ppm}$ measurement of the wavelengths thus provides a 1.8% measurement of the $2p\text{\ensuremath{-}}1s$ Lamb shift and is an improvement by a factor of 3 over previous work. Fitting the full two-dimensional dispersion relation, including Balmer and Lyman series, limits random and systematic correlation of parameters. Dominant systematics are due to diffraction parameters including crystal thickness and alignment, differential Doppler shifts due to the variable location of spectral emission downstream of the beam-foil target, and dielectronic, $2s\text{\ensuremath{-}}1s$, and $4f\text{\ensuremath{-}}2p$ satellites. Models developed are applicable to all relativistic plasma modeling in beam-foil spectroscopy at accelerators. The technique also reports the germanium $2{p}_{3∕2}\text{\ensuremath{-}}2{p}_{1∕2}$ fine structure as $397\phantom{\rule{0.2em}{0ex}}617\ifmmode\pm\else\textpm\fi{}251\ifmmode\pm\else\textpm\fi{}512\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, representing a 0.14% measurement of the fine structure and a 71% measurement of the QED contribution to the hydrogenic germanium fine structure, an improvement of a factor of 6 over previous work. We also report a precise measurement of heliumlike resonances and fine structure.

Beam–foil spectroscopy—Quo vadis?**Dedicated to the memory of Professor S Bashkin (20 June 1923–1 May 2007) and written in the honour of Professor L J Curtis (4 November 1935).

Beam–foil spectroscopy after 45 years: what has been realized of the promises? What is the state of the art? What is the status of the field? What present atomic physics problems should the technique be applied to, where can it be done? Will it be done?

Additions to the spectrum and energy levels and a critical compilation of helium-like and hydrogen-like boron, B IV and B V

Using beam-foil spectroscopy, we have observed several new lines in the B IV and B V spectra. This experimental work was combined with theoretical calculations using ab initio and semi-empirical techniques. We have also critically evaluated all previous and recent experimental and theoretical data for these spectra. Complete data on wavelengths and energy levels based on this analysis are tabulated.

Additions to the spectrum and energy levels and critical compilation of doubly ionized boron, B III

We have undertaken the study of the Li-like spectrum of doubly ionized boron, B III. The spectroscopic data have been obtained with beam-foil spectroscopy and high-resolution spark spectroscopy. The experimental work was combined with theoretical calculations using ab initio and semi-empirical techniques. About 50 new transitions have been observed, and most of the previously known lines have been measured with improved accuracy. We have also critically evaluated all previous and recent data for this spectrum. Complete data on wavelengths and energy levels based on this analysis are tabulated.

Charge and state population in dilute plasmas from beam-foil spectroscopy

Beam-foil spectroscopy has a long history for determining charge state evolution, radiative decay lifetimes, spectral widths, and satellite structure. Many theoretical results predict a range of populations and state dependencies, but high resolution or a very large bandpass is normally required to test or investigate these. The current investigation has tested some key assumptions and models as applied to this relativistic regime, particularly for few-electron iron resonances and satellites. We conclude that there are two specific production mechanisms, one inside the target to low-n levels and one dominated by capture mechanisms at the exit of the foil, with particularly significant Rydberg cascades. Several systematics in high-precision measurements of these systems are discussed and quantified for the first time. The 2s–1s and 4f–2p satellites are explicitly investigated, and a dominant systematic is uncovered that is due to the variable location of spectral emission, downstream of the beam-foil target. PACS Nos.: 32.70.Jz, 34.10.+x, 52.20.Hv, 34.60.+z

Lifetime and transition probability determination in xenon ions

Radiative lifetimes have been calculated for 15 levels of Xe VII belonging to the configurations 5s5p, 5p2, 5s5d, 5s6s, 5p5d, 4f5p, 5p5d and 5s5f and for 4 levels of the 5p and 5d configurations of Xe VIII. A relativistic Hartree-Fock approach including core-polarization effects, on the one hand, and a purely relativistic multiconfiguration Dirac-Fock method, on the other hand, have been used for the calculations. The accuracy of the present set of results has been assessed through comparisons with radiative lifetime measurements obtained by beam-foil spectroscopy. A good agreement between theory and experiment is observed for most of the levels. A new set of transition probabilities is proposed for 169 transitions of Xe VII and 45 transitions of Xe VIII.

Experiment and theory in interplay on high-Z few-electron ion spectra from foil-excited ion beams and electron beam ion traps

Spectroscopic measurements on few-electron high-Z ions take guidance from isoelectronic trends of low-Z to mid-Z ions and from theory. Such wide-range extrapolations, however, are fraught with uncertainty. We discuss as examples some n = 3, Δn = 0 transitions in the EUV spectra of Na-, Mg- and Al-like ions of Au that have been observed by electron beam ion trap work and by heavy-ion accelerator based beam-foil spectroscopy. New insights are gained from notable recent progress of calculations.

Relativistic multireference many-body perturbation theory calculations on Au64+ - Au69+ ions

Many-body perturbation theory (MBPT) calculations are an adequate tool for the description of the structure of highly charged multi-electron ions and for the analysis of their spectra. We demonstrate this by way of a re-investigation of n=3, Δn=0 transitions in the EUV spectra of Na-, Mg-, Al-like, and Si-like ions of Au that have been obtained previously by heavy-ion accelerator based beam-foil spectroscopy. We discuss the evidence and propose several revisions on the basis of our multi-reference many-body perturbation theory calculations of Ne- through P-like ions of Au.

Radiative lifetime and oscillator strength determinations in potassium ions (K V, K VI and K VII)

Oscillator strengths have been calculated for the transitions depopulating levels of the 3s23p3, 3s3p4 configurations of K V, of the 3s23p2, 3s3p3 configurations of K VI and of the 3s23p, 3s3p2, 3p3 and 3s3p3d configurations of K VII. A multiconfiguration Dirac-Fock method, incorporating the relativistic two-body Breit interaction and quantum electrodynamics corrections due to self-energy and vacuum polarization, has been used for the calculations. The reliability of this approach has been tested by comparison with relativistic Hartree-Fock calculations and also with some experimental measurements performed by beam-foil spectroscopy at a beam energy of 1.7 MeV.

Energy levels and spectral lines of Ne VII

All experimental data on the valence-shell-excited and core-excited spectra of Li-like neon, including previously unpublished beam-foil spectroscopy data, have been compiled and critically evaluated. Seventeen spectral lines have been newly identified. Sets of recommended energy levels have been derived from the total list of observed lines and from selected results of theoretical and semi-empirical calculations. An accurate value of the ionization potential has been derived from existing theoretical calculations.

Precision lifetime measurement of the 2p 2P3/2 level for Li-like Ni by beam-foil spectroscopy

In this paper we present a precise and reliable measurement of the 1s22p 2P3/2 lifetime for Li-like Ni. The measurement was done using the technique of beam-foil spectroscopy employing a beam of 5.9MeV/u Ni from the UNILAC accelerator at GSI. Special attention was taken concerning satellite blending and foil-ageing problems to justify the reliability of the lifetime value extracted from the measured decay curve. The experimental value for the 2p 2P3/2 lifetime, 0.168±0.006ns, is found to be in very good agreement with theoretical results.