Solid state physics at ISOLDE

Radioactive atoms have been used in solid state physics and in materials science for decades. Besides their classical applications as tracers for diffusion studies, nuclear techniques such as Mössbauer spectroscopy, perturbedγγ angular correlation,β-NMR, and emission channeling make use of nuclear properties (via hyperfine interactions or emittedα orβ particles) to gain microscopic information on structural and dynamical properties of solids. During the last decade, the availability of many different radioactive isotopes as clean ion beams at ISOL facilities like ISOLDE/CERN has triggered a new era involving methods sensitive to the optical and electronic properties of solids, especially in the field of semiconductor physics. This overview will browse through ongoing solid state physics experiments with radioactive ion beams at ISOLDE. A wide variety of problems is under study, involving bulk properties, surfaces and interfaces in many different systems like semiconductors, superconductors, magnetic systems, metals and ceramics.

     

Study of nuclear reactions with radioactive 17F at HRIBF

Radioactive ¹⁷F beams were produced at the Holifield Radioactive Ion Beam Facility (HRIBF) using the Isotope Separator On-Line (ISOL) technique. Two of the experiments using accelerated ¹⁷F beams to study reaction mechanisms are presented: the simultaneous emission of two protons from a resonance in ¹⁸Ne and the breakup of ¹⁷F by ²⁰⁸Pb.     

19F nuclear relaxation study of the fluorite system Pb0.84Bi0.16F2.16

Abstract

Measurements of the ¹⁹F nuclear relaxation times are reported for the fluorite-structured Pb_0.84Bi_0.16F_2.16 single crystal. The formation of clusters by thermal treatment, as revealed by changes in the fluorine T ₂ during temperature cycling, is discussed.     

Book Reviews

Abstract

Restoration of Environments with Radioactive Residues International Atomic Energy Agency, Proceedings of an International Symposium, Arlington, Virginia, USA, 29 November -3 December 1999. Vienna 2000.697 pp. Proceedings Series, ISSN 0074-1884

Regularity Control of Radioactive Discharches to the Environment. Safety Guide Safety Standards Series No. WS-G-2.3. International Atomic Energy Agency, Vienna 2000. 43 pp.     

Bayesian Logical Data Analysis for the Physical Sciences,edited by P.C. Gregory

(1) Combined Effects of Radioactive, Chemical and Thermal Rebases to the Environment. Proceedings of a Symposium held in Stockholm, 2–5 June 1975. Vienna, 1975. International Atomic Energy Agency. London, H.M.S.O., pp. 358. £10·00.

(2) Impacts of Nuclear Releases into the Aquatic Environment. Proceedings of an International Symposium held at Ontaniemi, Finland, 30 June—4 July 1975. Vienna, 1975. International Atomic Energy Agency. London, H.M.S.O., pp. 524. £14.60.     

Nuclear Astrophysics with Radioactive Beams

Radioactive beams, either at low or high energy, can be very useful for understanding violent events which are encountered in nuclear astrophysics.     

Ion bombardment-induced charge state effects CaO single crystals: F+ and F centers

The effects of heavy-and light-ion bombardment on defect formation in CaO have been investigated by UV-absorption spectroscopy and volume measurements. While 500 keV Ar or Ca implantation produces only F⁺ centers, 240 keVH produces both F⁺ and F centers at a F⁺ to F ratio of 5.6 to 1. On the other hand, when an argon implanted sample is subsequently bombarded with hydrogen, about 30% of the F⁺ centers anneal during 1 ×10¹⁴ H/cm²; at higher H fluences, new F⁺ and F centers are produced. An effect of energy partition between ionization and nuclear/atomic collision processes for the incident ions on the charge state of the resulting defect is thus clearly demonstrated.

The formation and annealing of these defects are accompanied by volume changes in the ion implanted surface layer which can be monitored in sltu with a cantilever beam technique. The measurements show volume expansion of the order of 1.5% following 10¹⁶ 500 keV Ar implantation; subsequent implantation of 10¹⁸ 240 keV H compacts the previously expanded material by 25 %. These results are in qualitative agreement with the optical data and seem to indicate that volume changes are associated with the formation and annealing of F⁺ centers.     

Tokai Radioactive Ion Accelerator Complex (TRIAC)

An ISOL-based radioactive nuclear beam (RNB) facility, Tokai Radioactive Ion Accelerator Complex (TRIAC), has been jointly developed by High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Agency (JAEA). The facility started to supply RNBs for experiments in 2005 and RNBs including fission fragments with energies up to 1.1MeV/A are available in the present. Several experimental studies were performed successfully using ⁸Li beams with various energies.     

Hydrogen Bond and 19F NMR Chemical Shift Akisotropy in Apatite

Abstract

The fluoroapatite minerals, Ca₅-F(PO₄)₃ usually contain some hydroxyis, instead of fluorine. From infrared spectra it was concluded, that there are weak hydrogen bonds OH … F along apatite hexagonal axis¹. In order to receive more detailed information about the character of F^?and OH^?bonds with the nearest atoms in apatites we studied the nuclear magnetic resonance (NMR) spectra of protons and fluorines in natural apatite single crystal, in which approximately 15% of fluorines is substituted by hydroxyis.     

Nuclear magnetic relaxation by spin-rotation interaction.

Spin-rotation interaction constants, c, are calculated from the paramagnetic term of the nuclear magnetic shielding constant, σ _p, using a relationship originally due to Ramsey. Calculated values show excellent agreement with experimental determinations from molecular beam measurements. Since σ _p can be easily estimated from the chemical shift of the nuclear resonance this provides a general method for estimating spin-rotation interaction constants.

Chemical shift anisotropies allow the components c _⊥ and c _‖ of the spin-rotation interaction tensor to be determined. Generally both components have the same sign and are of similar magnitude. The r.m.s. value of the spin-rotation interaction constant, required to calculate nuclear spin-lattice relaxation times, is not expected to differ appreciably from average values obtained from molecular beam measurements or magnetic shielding.

Values for the molecular angular velocity correlation time, τ _sr, calculated directly from nuclear spin-lattice relaxation times are about a factor of four longer than those predicted by the relationship between τ _sr and the re-orientation correlation time, τ _d, as given by Hubbard.     

Range and energy-loss of 16.34 Mev/u 238U in kapton polyamide

Abstract

The range and energy-loss of 16.34 MeV/u ²³⁸U in Kapton-polyamide plastic have been measured by the nuclear track technique. The experimental ranges are compared with two sets of theoretical values. It has been observed that ranges obtained from the computer code ‘DEDXT’ are found to be 5–8% lower as compared to measured ones whereas those from Northcliffe and Schilling are about 10–15% overestimated above 8 MeV/u.     

Optical,magneto-optical and structural properties of F centres in BaFBr

Abstract

In BaFBr, a material which can be used as a storage phosphor for X-rays, two types of F centres can be created by additive coloration or by X-irradiation. The properties of both F centres which play an important role in the storage phosphor mechanism were investigated with optical and magneto-optical methods. The absorption bands, the emission bands, production, and stability of the F centres are discussed.     

1H, 13C and 19F NMR Studies of the Diels-Alder Adduct of p-Fluoranil with Phencyclone. II. Hindered Phenyl Rotations and Anisotropic Effects in a Model Compound for Drugs

Abstract

The Diels-Alder adduct of phencyclone, compound 1, with p-fluoranil, compound 3, has been prepared in refluxing toluene. The adduct, compound 2, has been examined by ¹H, ¹³C and ¹⁹F NMR spectroscopy at 300, 75 and 282 MHz, respectively. At ambient temperature, the unsubstituted bridgehead phenyl groups in adduct 2 are found to exhibit hindered rotation, resulting in slow exchange limit (SEL) ¹H NMR spectra. Full aryl proton assignments are made based on 1D and 2D (COSY45) NMR. The ¹⁹F NMR (proton coupled) reveals one of the two ¹⁹F signals to be a triplet. This resonance collapses to a singlet in the proton decoupled ¹⁹F spectrum, implying an unexpected long range ¹H-¹⁹F coupling. For the ¹³C NMR spectrum, tentative assignments are presented. Data for compound 2 as a model compound for drugs are discussed in terms of the hindered aryl rotation and evidence of magnetic anisotrppic effects.     

Locations of implanted 19F* atoms in Si,Ge and diamond studied through their nuclear quadrupole interactions

The Hartree-Fock cluster procedure was used to obtain the associated electronic distributions for ¹⁹F^* (I = 5/2, E ^x = 197 KeV excited nuclear state of the ¹⁹F atom) at possible sites in crystalline Si, Ge and diamond and to calculate nuclear quadrupole coupling constants v _Q and the asymmetry parameter η of the electric field gradient at the modelled sites. Lattice relaxation effects have been incorporated by employing a geometry optimization method to obtain minimum energy configurations for the clusters modelling each site. The intrabond (IB), antibonding (AB) and substitutional (S) sites in the bulk and the atop site on the surface were studied. From a comparison with v _Q and η values observed in time differential perturbed angular distribution (TDPAD) measurements we were able to identify the high frequency component in Si and Ge with ¹⁹F^* at the intrabond site. In diamond two high frequency components are observed. These are identified with ¹⁹F^* at intrabond and substitutional sites. For the low frequency site in Si and Ge the assignment is made to ¹⁹F^* implants at dangling bonds in the bulk resulting from implantation damage. In diamond none of the sites studied could provide lower frequency nuclear quadrupole parameters close to the observed ones. This revised version was published online in August 2006 with corrections to the Cover Date.     

The assessment of risk in relation to major hazards,with particular reference to nuclear reactors

The article concentrates mainly on the developing pattern of safety thinking and safety practices which have been brought about by, and in turn have influenced, the growth of modern industrial technology, particularly in the nuclear field.

The need to minimize the chance of accidents with serious consequences led to pursuit of safety by siting, by containment and by automatic built-in safety mechanisms; these are discussed.

Codes of practice and safety guidelines are becoming linked with more quantitative goals to achieve desired objectives in safety and reliability. This is particularly important in the assessment of major hazards.     

The decay scheme of 127Ba and half-lives of some low-lying excited states in 123, 125, 127, 129Cs

Radioactive sources of ^{123, 125, 127, 129}Ba obtained in the spallation reaction have been studied with Ge(Li), Si(Li), NaI(Tl) and plastic detectors. On the basis of γ-ray energies, intensities, energy sums and coincidence information, the decay scheme has been proposed for ¹²⁷Ba. No high-spin isomer of ¹²⁷Ba has been observed. The lifetimes of $\text{5}\text{2}$⁺ → $\text{1}\text{2}$⁺ transitions in ^{123, 125, 127, 129}Cs have been measured. No evidence for the shape isomerism in ¹²⁷Cs has been found.     

Book Reviews

Abstract

Guidelines for Agricultural Countermeasures Following an Accidental Release of Radionuclides. (TECHNICAL REPORTS SERIES No. 363, IAEA Vienna, 1994, 115 pp.)

Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments. (TECHNICAL REPORTS SERIES No. 364, IAEA Vienna 1994, 74 pp.)

Sources and Magnitude of Occupational and Public Exposures from Nuclear Medicine Procedures. Recommendations of the National Coouncil on Radiation Protection and Measurements. NCRP Report No. 124 Bethesda, MD, USA, 1996, 77 pp.

Deposition, Retention and Dosimetry of Inhaled Radioactive Substances. Recommendations of the National Council on Radiation Protection and Measurements. NCRP Report No. 125, 253 pp., Bethesda, MD, 1997, $40.     

Precise Mass Calculations for Atomic Nuclei of Isospin Tz = 51/2, 26, 53/2, 55/2, 28, and 57/2 with Restored Spin-Isospin SU(4) Symmetry

Via simulating the contribution of spin-orbit interaction to nuclear masses by orthogonal Chebyshev polynomials, the mass excesses are calculated for a group of atomic nuclei characterized by the isospins of T_z = 51/2, 26, 53/2, 55/2, 28, and 57/2 and by the presence of restored Wigner’s spin-isospin SU(4) symmetry. The root-mean-square deviation of the results of these calculations from their experimental counterparts is σ = 140 keV. The potential of the proposed method is discussed.

     

Neue Referenzpräparate für die quantitative Autoradiographie und andere kernmeßtechnische Prüfverfahren

Radioactive surface reference sources are represented. The radionuclides in these sources are embeded into epoxy resins. Two new types of sources were developed for the calibration and standardization ofautoradiograms: The Tc-99 step wedge references source and the beta calibration set. Further on radioactive labelled surface sources for different nuclear measuring methods using as reference sources are described. These sources are labelled with Co-57, Co-60, Ni-63, Sr-90/Y-90, Tc-99, Ba-133, Cs-137, Pm-147, Eu-152, Tl-204, Am-241. The lowest density per unit area is 5 mg · cm^?2, the maximum area of a source is 300 cm². Commonly the radioactivity concentration amounts from 5 Bq · cm^?2 to 50 kBq · cm^?2, higher concentration is possible.     

F and F2 centres in LiF induced by ion implantation

Abstract

COMPUTER IMAGE PROCESSING AND RECOGNITION, by Ernest L. Hall, Academic Press, New York, 1979. Price: $41.35.

SAFETY IN THE CHEMICAL LABORATORY, by N. T. Freeman and J. White-head. Academic Press, London, 1982. ISBN 0 12 267220 8. 244 pages. $43.10.

A DICTIONARY OF SPECTROSCOPY, by R. C. Denney. Macmillan Reference Books, London. Second Edition, 1982. ISBN 0 333 31670 3. 205 pages. €15.

WOMEN SCIENTISTS: THE ROAD TO LIBERATION, Edited by Derek Richter, McMillan, London, 1982. 219 pp. €10.00.

ION ASSISTED SURFACE TREATMENTS, TECHNIQUES AND PROCESSES. Conference Proceedings, Warwick, U.K., 14–16 September 1982. 1982, The Metals Society, ISBN 0 904357 48 1, €00.0