Survey of experimental results on μCF including hyperfine effects

Complementary to the investigations of the most efficient dt cycle, also the other muon-induced fusion cycles in mixtures of hydrogen isotopes have been studied. The results of these dedicated experiments provide rich information about muon-induced few-body reactions and contribute significantly to a better overall understanding of CF. A summary of the recent progress will be presented. Special emphasis will be put on two characteristic examples, namely a new experimental approach to study the muonic cascade in H-D mixtures and the systematic study of hyperfine effects in muon-induced reactions.     

High precision study of muon catalyzed fusion in D2 and HD gas

Muon catalyzed dd fusion in D₂ and HD gases in the temperature range from 28 to 350 K was investigated in a series of experiments based on a time-projection ionization chamber operating with pure hydrogen. All main observables in this reaction chain were measured with high absolute precision including the resonant and non-resonant ddμ formation rates, the rate for hyperfine transitions in dμ atoms, the branching ratio of the two charge symmetric fusion channels ³He + n and t + p and the muon sticking probability. The report presents the final analysis of the data together with a comprehensive comparison with calculations based on recent μCF theories. The energy of the loosely bound ddμ state with quantum numbers J = 1, ν = 1, which is central to the mechanism of resonant molecule formation, is extracted with precision ?₁₁(fit) = ?1.9651(7) eV. in impressive agreement with the latest theoretical results ?₁₁(theory) = ?1.9646 eV.     

Microanalysis by Laser Ablation-Inductively Coupled Plasma-Atomic Emission Spectrometry in Comparison to Spark Ablation of Certified and Found Minerals Galena, Sphalerite, and Pyrite

A double-tandem technique of inductively coupled plasma-atomic emission spectrometry (ICP-AES) involving laser ablation for the analysis of compact or briquetted minerals on one hand and spark ablation for the analysis of powders on the other is presented. The technical arrangement, the design of the optimized sample chamber, the evaluation of operating conditions, and the test of liquid-solid calibration are described. Both techniques can be used for the determination of elemental compositions of minerals providing a dynamic range from tens of mass-percent down to milligrams per kilogram. The objective of this study was to compare laser ablation (LA)-ICP-AES and spark-ICP-AES with regard to accuracy, precision, and sample turnaround time for multielement analysis of the certified minerals galena GF1, sphalerite SF1, and pyrite PS1. A systematic error of smaller than 3% in both techniques and a random error of smaller than 9 and 5%, respectively, is pointed out. The optimized methods were applied to samples of galena, sphalerite, and pyrite from four deposits each to find fingerprints by different contents of major, minor, and trace elements, which characterize the deposits.     

Resonant formation measurements of dt\mu via time of flight

Solid hydrogen in the form of an inhomogeneous layered target offers several experimental advantages when compared with liquid or gas. Beams of non-thermalized muonic hydrogen atoms allow us to explore resonant molecular ion formation processes near eV kinetic energies. Isotopically specific layers make it possible to separate competing and confusing interactions and to employ the time of flight for comparison with predictions based on theoretical energy dependences. Unambiguous charged fusion product detection simplifies absolute intensity measurements. The systematic uncertainties encountered in resonant molecular ion formation measurements, using solid hydrogen target layers, are being investigated with simulations which use the many calculated energy-dependent rates and cross-sections which are now available. The importance of the rates for processes such as muon transfer and elastic scattering are discussed, and results of some recent analyses are presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

A new project for the investigation of unsolved problems of ddµ and pdµ catalysis in D2 and H/D mixtures

We propose to study a number of open problems in ddµ and pdµ fusion using the new high-pressure ionization chamber for charged particle identification in coincidence with the n-/e-counter array for the detection of neutrons and µ-decay electrons. Our first objective will be a precise measurement of the absolute rates of resonant and non-resonant ddµ formation in D₂ and HD-gases and their temperature dependence from 40 to 350 K. Both output channels of the dd-reaction:³He + n and t + p will be observed and their ratio sensitive to contributions of S and P-waves will be determined. Simultaneously, we shall investigate the pdµ-cycle and determine the absolute pd-fusion yields in different molecular H/D compositions, observing tritons from nuclear muon capture in³Heµ: pdµ ³Heµ + . We have developed a special system for the preparation of HD-gas with high concentration (96%) of HD and a purity (10^–6).     

Generation of 4,5-Diazacyclopentane-1,3-diyl Radical Cations by Chemical Electron Transfer (CET) Oxidation of Urazole-Bridged Bicyclic Housanes (Bicyclo[2.1.0]pentanes) and Their Chemical Transformations

4,5-Diazacyclopentane-1,3-diyl radical cations 3(*)(+)() were generated from urazole-bridged bicyclic housanes 3 through chemical oxidation by using tris(4-bromophenyl)aminium hexachloroantimonate as oxidant to afford the two olefinic products 4 and 5. Product studies establish that the bisolefins 5 are the result of double oxidation of the housanes 3, whereas the monoolefins 4 are formed by acid-catalyzed rearrangement, which can be suppressed by excess of base (2,6-di-tert-butylpyridine). In the case of dibenzyl substitution (3c), disproportionation of two monoradical species 5(H)c(*) serves as an alternative pathway to the corresponding olefins 4 and 5 because higher amounts of double oxidation product were isolated in the absence of base than expected if only a stoichiometric reaction were operating. Semiempirical MO calculations suggest that ionization takes place from one of the nitrogen lone pairs rather than from the strained central C-C bond as implied by the significantly lower (by ca. 0.5 eV) ionization potential. Furthermore, in the initially puckered radical cation, the positive charge is mainly located at the two nitrogen atoms, while after relaxation to the planar geometry, the charge shifts essentially entirely to the radical cation carbon atoms. The trapping reaction with methanol leads to the hemiaminal-type products 6 and 7, which establish the involvement of the cationic intermediates 3(H)(+)() and 5(H)(+)(). In addition, (13)C NMR spectroscopy confirmed these cationic intermediates [3(H)(+)() and 5(H)(+)()] by detection of the characteristic signals below delta 250 for carbenium ions. Unquestionably, the urazole ring significantly influences the radical cation reactivity of the housanes 3. Thus, in contrast to the corresponding homocyclic tricyclooctane derivatives, stoichiometric instead of catalytic amounts of CET oxidant are needed, the two nitrogen atoms of the hydrazino bridge stabilize the radical cation 3(*)(+)() by conjugation, and the carbonyl groups of the urazole moiety assist the deprotonation to the exocyclic double bonds to prevent 1,2 alkyl migration.     

μCF Experiments in D2 and HD Gases – Final Results

During 1994–1996, a series of μCF experiments were performed at PSI by the PSI-PNPI-IMEP-LBNL-TUM collaboration. These experiments aimed at high-precision studies of the d–μ–d fusion in D₂ and HD gases in a wide temperature range. The Gatchina ionization time projection chamber has been used to detect the dd-fusion reaction products. The main parameters of the d–μ–d fusion have been measured with high absolute precision. In this report, we present the results of the final analysis of the experimental data. The obtained results are compared with the calculations based on a recent μCF-theory. This revised version was published online in August 2006 with corrections to the Cover Date.