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The present situation of muon transfer to helium is summarized. A new gas target for a maximal pressure of 40 b with four thin beryllium windows for the detection of low energy photons is described. First results of an analysis of the time spectra of muonic carbon X-rays in a H2+CH4 gas mixture taken with the new target show a pressure dependent structure.

By analysing the time spectra of the muonic sulphur X-rays in seven different H2+SO2 gas mixtures, the muon transfer rates to the SO2 molecule, deduced from the lifetimes of the µp atoms, agree all well with each other. The muonic oxygen time spectra show an additional structure as if µp atoms of another kind were present. Reduced transfer rates Λ o ′ are reproducible if one uses the model of “ephemeral” µp atoms[1].

Experiments are described which use a solid hydrogen layer to form muonic hydrogen isotopes in vacuum. The method relies on transfer of the muon from protium to either a deuteron or a triton. The resulting muonic deuterium or muonic tritium will not immediately thermalize because of the very low elastic cross sections, and may be emitted from the surface of the layer. Measurements which detect decay electrons, muonic x-rays, and fusion products have been used to study the processes. A target has been constructed which exploits muonic atom emission in order to study the energy dependence of transfer and muon molecular formation.

The muonic atom 2${\mathit{p}}_{1/2}$-1${\mathit{s}}_{1/2}$ and 2${\mathit{p}}_{3/2}$-1${\mathit{s}}_{1/2}$ transition energies were measured with an experimental accuracy of better than 20 ppm for the isotope chain $^{112,114,116,117,118,119,120,122,124}\mathrm{Sn}$. Precise values for the Barrett equivalent nuclear radii ${\mathit{R}}_{\mathit{k}\mathrm{\ensuremath{\alpha}}}$ and their differences as well as root-mean-square radii were deduced. The \ensuremath{\Delta}N=2 isotope shifts between the even Sn isotopes show a subshell effect at the neutron number N=64. Otherwise, there is a nearly linear decrease with increasing N, in accordance with the general systematics of nuclear charge radii. Our muonic atom results are in a good agreement with recent optical data, including odd-even staggering. Hartree-Fock calculations reproduce the general trend but not the subshell effect. Regarding the nuclear polarization corrections, the problem in the 2p splitting found earlier in ${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$-Zr and ${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$-Pb seems also to persist in ${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$-Sn.

The muon transfer process in binary and ternary gas mixtures with hydrogen looks like a well known process. 1 From the ground state of the up atom, where the muon has a binding energy of about 2.6 keV, the muon is transferred to higher Z elements onto atomic orbits with much smaller radii than the outer electron shells of the atom Z, and where the muon has a comparable binding energy. The transfer process does therefore not depend on chemical structures and bonds in which the element, to which the muon is transferred, is involved.

A negative muon, captured in a mixture of natural hydrogen with a small amount of another gas of atomic number Z, forms a muonic hydrogen or a muonic Z atom in an excited state. In the deexcitation process, muonic X rays are emitted. Because the cascade time is very short (of the order of 10–12 s at 10 bar), they appear promptly with regard to the incoming muon. After deexcitation of the (μp)* system (in about 10–10s), which occurs essentially by collisions, 1 the (up) is atom can then disappear by muon decay with an associated rate λ0, by formation of a pup mesomolecule (λpp), or by transferring the muon to deuterium (λd) or to the Z element (λpz). The total disappearance rate of the up atom, λ is then: $$\lambda = {\lambda _{0}} + {\lambda _{{pp}}} + {\lambda _{d}} + {\lambda _{{pZ}}}$$ (1)

Weed suppression and nitrogen (N) management present the greatest challenges to organic growers. Cover crops, the strategic use of tillage, and multiple nitrogen sources are being investigated in order to develop integrated management practices. Combinations of legume and grass cover crops are being utilized as alternative N sources and as tools for weed suppression. Another objective is to compare conventional and no-till practices to determine when the strategic use of tillage is most beneficial for N management and weed control. The last objective is to evaluate the fate of applied N and N released from cover decomposition on crop development. The best combinations of cover crop species, the frequency and intensity of tillage, and optimum N rates will be determined for the production of organic broccoli. This project will aid growers interested in transitioning to organic farming. In addition, integrated management practices that balance the short-term needs for crop productivity and the long-term interests of sustainable production will be reported.

In the spectrum of muonic X-rays of238U measured in coincidence with prompt fission events a structure has been found which is attributed to 2p→1s transitions of the muon attached to heavy fragments. The intensityI s of this structure relative to the strengthI pf observed for prompt fission has been determined to beI s/I pf=(6.0± 2.1) %. Although the experimental significance for the appeareance of this phenomenon is weak, this is the first experimental indication for its occuxence.

The Tables summarize experimental results from muonic atom transition energies, nuclear charge parameters from elastic electron scattering, and K x-ray isotope shifts in so far as they provide information on nuclear ground-state charge radii. Numerous experimental results for optical isotope shifts have been published elsewhere; for eight elements the relevant information is condensed ("projected") here to one optical line per element. A model-independent analysis which combines data from all three experimental methods is applied to these elements and is presented as an illustration of the improved accuracy for the rms radii and Barrett radii which result from this analysis.

The muonic Coulomb capture ratio A(${\mathrm{H}}_{2}$,Ar) has been measured in two different ${\mathrm{H}}_{2}$-Ar gas mixtures using two different methods of evaluation based on the muon transfer from hydrogen. The measured ratios agree with each other, but disagree with the corresponding pionic capture ratio and also with the ratios calculated from muonic and pionic A(He,Ar) and A(He,${\mathrm{H}}_{2}$) capture ratios. The large discrepancies might be related to unsolved problems in muon transfer.

By analysing measured time distributions of the muonic oxygen and sulphur X-rays in a H2+SO2 gas mixture, one finds two different time constants. If these correspond to two lifetimes for the bound μp atom, two kinds of μp atoms exist: one kind transfers its muon only to oxygen, the other to both oxygen and sulphur. The difference in the two μp systems is presently unexplained.

The X-ray spectrum of muonic 237 Np has been investigated with stopped muons in a NpO 2 target, containing about 10 g of 237 Np. The probability of the radiationless muonic 3d→1s transition in 237 Np , (9±4)% , was obtained by comparing the relative intensities of the main muonic X-ray transitions in singles and coincidence spectra. The coincidences were gated by the 2p→1s transitions.

The transfer of negative muons from the ground state of muonic hydrogen to argon and helium has been measured in gaseous mixtures at pressures between 10 and 15 bars and at different relative concentrations. The transfer rate to argon, reduced to liquid-hydrogen density [${\ensuremath{\Lambda}}_{p\mathrm{Ar}}$ =1.42(4)\ifmmode\times\else\texttimes\fi{}${10}^{11}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$], agrees well with those obtained at ten times higher pressures. The transfer rate to helium [${\ensuremath{\Lambda}}_{p\mathrm{He}=0.88(9)\ifmmode\times\else\texttimes\fi{}{10}^{8}}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$], measured in a triple gas mixture, disagrees with the only other experimental value and is about two times higher than recent theoretical predictions. In addition, the muonic x-ray intensities of the Lyman series of argon resulting from muon transfer have been determined. They are well reproduced by a cascade calculation assuming a theoretical initial distribution over n and l states.

Energies and intensities of 53 nuclear γ-lines in muonic atoms of Sm, Gd, Eu, Tm, Yb, Ta, W, Re, Os, Ir, Pt, Hg, Tl, and Bi have been measured with Ge(Li) detectors. By comparison with γ-lines from radioactive sources the isomer shifts for transitions from nuclear rotational levels, quadrupole and octupole vibrational levels, and single-particle levels have been deduced. The effect limiting the accuracy of the extracted isomer shifts is the correction for the magnetic hyperfine splitting of the nuclear levels.

Muonic X-ray energies of the K-series of the light natural elements Be, B, C and N have been determined with a precision of 5 to 10 eV. Equivalent nuclear charge radii have been deduced. The results, expressed in terms of rms radii, are of similar or better accuracy than recent electron scattering data. Of particular interest is the rms radius of carbon as a reference value for elastic electron scattering cross sections. A model-independent evaluation yields 〈r 2 〉 1 2 = 2.467 (17) fm .

Single-crystal X-ray data (Mo Kα radiation) are reported for the following: 1. (i) Y3Os4Si12 (orthorhombic, Er3Ru4Si12 structure type, oS76, Cmca, a = 18.495(2) A , b = 8.125(1) A , c = 8.130(1) A , V = 1221.7 A 3 , Z = 4, Dx = 7.417 g cm−3, R = 0.096 for 927 contributing independent reflections); 2. (ii) Y5Os4Si14 (monoclinic, Lu5Co4Si14 structure type, mP46, P21/c, a = 12.779(5) A , b = 8.019(3) A , c = 7.926(3) A , β = 98.69(3)°, V = 802.9 A 3 , Z = 2, Dx = 6.611 g cm−3, R = 0.076 for 2336 reflections); 3. (iii) Y9Os4Si20 (monoclinic, new structure type. mP66, P21/c, a = 19.417(1) A , b = 7.949(3) A , c = 8.005(3) A , β = 95.92(1)°, V = 1229.0 A 3 , Z = 2, Dx = 5.735 g cm−3, R = 0.069 for 1840 reflections). The structures are members of a structure series which is obtained by one-dimensional stacking of two types of two-dimensional structural segments. The principal segment has the composition [Y3Os4Si12] (i) or [Y3Os4Si10] ((ii) and (iii)) and is intergrown either with itself (i), or with segments of silicon-centred yttrium prisms having the AIB2-type structure (ii), or the silicon-deficient α-ThSi2-type structure (iii).

We have determined the magnetic hyperfine structure (HFS) in four nuclear transitions of muonic 209Bi. The results yielded an improved value of the magnetic HFS constant of the ground state. A 1 ( 9 2 − ) = 2.00 (7) keV . New experimental values were established for three excited states, namely A 1 ( 13 2 + ) = 2.9 (2) keV , A 1 ( 9 2 + ) = 2.1 (2) keV and A 1 ( 15 2 + ) = 2.4 (2) keV . In addition, the isomer shifts (IS) of the above-mentioned transitions were determined making use of the HFS constants. We find the following IS's of excited states: 13 2 + , 3.77 (28) keV ; 9 2 + , 6.56 (32) keV ; 15 2 + , 6.29 (18) keV .

The energies of muonic x-ray transitions sensitive to the nuclear charge parameters have been measured with a precision up to 9 ppm in muonic /sup 90/Zr. Combining our muonic-atom results for the equivalent nuclear charge radii R/sub k/,..cap alpha.. with recent elastic electron scattering data, the rms radius of /sup 90/Zr could be determined as /sup 1/2/ = 4.2726(9) fm. In addition to the nuclear monopole charge distribution, nuclear polarization correlations between the muonic 1s and 2s and the 1s and the two 2p states could be determined. With additional constraints from elastic electron scattering and theory, the nuclear polarization corrections of the four lowest-lying states could be evaluated with precisions of the order of 15%. Of particular significance is the result for the two 2p states, because the experimentally determined 2p/sub 1/2/ correction is smaller than the nuclear polarization correction in the 2p/sub 3/2/ state, in contrast to current theoretical models.

The transfer rate of negative muons from the 1s state of hydrogen to argon has been measured in H2+Ar gas mixtures at total pressures of 100 and 140 bar and argon concentrations C (Ar/H2) of 6*10-4 and 20*10-4. The reduced transfer rates have been found to be independent of the total pressure and of the argon concentration. The mean reduced transfer rate obtained, Lambda pAr=(1.46+or-0.05)*1011 s-1, is compared with the rates measured by other authors.

The osmium-silicon phase diagram was investigated by means of X-ray powder diffraction, differential thermal analysis, metallography, microprobe analysis and electrical resistivity measurements. The existence and type of formation of the following intermetallic compounds was established: OsSi, Os 2 Si 3 and OsSi 2 . These three compounds are semiconducting. A metastable phase was found at 67 at.% silicon.

Energies of muonic x rays of the Lyman series of the even sulphur isotopes /sup 32/S, /sup 34/S, and /sup 36/S and of natural phosphorus have been determined with absolute precisions up to 23 parts/10/sup 6/. Equivalent Barrett charge radii R/sub k/,..cap alpha.. have been deduced. Their differences between the sulphur isotopes amount to ..delta..R/sub k/,..cap alpha..( /sup 34/S- /sup 32/ S) = 29.7(1.4) am and ..delta..R/sub k/,..cap alpha..( /sup 36/S- /sup 34/ S) = 18.7(1.5) am. Combining these results with recent elastic electron scattering data, we obtain in a model-independent way ..delta../sup 1/2/( /sup 34/S- /sup 3/ 2S) = 23.1(1.2) am and ..delta../sup 1/2/( /sup 36/S- /sup 3/ 4S) = 13.0(1.2) am.

Muonic x-ray intensities of the Lyman series have been measured in carbon (diamond, graphite, and soot) and in boron and nitrogen in the cubic (diamond) and hexagonal (graphite) structures of boron nitride. By means of muon cascade calculations which reproduce the measured intensities, angular momentum distributions of the captured muons have been determined for carbon and nitrogen in the $\ensuremath{\mu}$-atomic level $n=13$. The boron-to-nitrogen capture ratios have been found to be 0.233\ifmmode\pm\else\textpm\fi{}0.011 in the cubic structure and 0.275\ifmmode\pm\else\textpm\fi{}0.012 in the hexagonal structure. The difference of 18\ifmmode\pm\else\textpm\fi{}3% has to be attributed to the difference in the solid-state structures.

In order to test the QED corrections, and in particular the vacuum polarization, muonic 4f-3d transitions in Ba and Ce and 5g-4f transitions in Tl and Pb have been measured using Ge(Li) detectors. An absolute energy accuracy of ± 8 eV corresponding to a relative error of 17–19 ppm has been obtained. The experimental energies agree with theory within the total uncertainty of ± 10 eV. This corresponds to a test of the QED vacuum polarization calculations of between 0.35 % and 0.50 %.

Crucible corrosion is one of the major obstacles to obtaining large crystals of the high-temperature superconductor YBa2Cu3O7-x. The crucible-melt interfaces of three types of ceramics (alumina, zirconia and tin oxide) have been studied in order to understand the corrosion mechanism. This may help to reduce the crucible problem in crystal growth of YBCO and to indicate alternative crucible materials of improved corrosion resistance.

Energies of muonic X-rays of the Lyman series of seven light natural elements (F, Na, Al, Si, P, S and K) have been determined with an accuracy of between 15 and 30 eV. Equivalent charge radii have been deduced. For μ−-K, transitions to the 2s state allowed an additional constraint on the Fermi c-t diagram. The results are in good agreement with, and generally of an order of magnitude higher precision than, comparable electron scattering data.

The rhodium-silicon phase diagram was investigated by means of X-ray powder diffraction, differential thermal analysis, metallography and electrical resistivity measurements. The existence of nine intermetallic phases was established: Rh2Si, Rh5Si3, Rh20Si13, Rh3Si2, RhSi-l, RhSi-h, RhSi-x, Rh4Si5 and Rh3Si4. Rh20Si13 is a high temperature phase which decomposes eutectoidally at 1050 ± 20 °C. At the stoichiometric composition RhSi, three different structures were found: an orthorhombic low temperature phase (RhSi-l), a cubic high temperature FeSi-type phase (RhSi-h) and a monoclinic and probably martensitic phase (RhSi-x). The CsCl-type RhSi mentioned in the literature was not found in this study. One of the phases, Rh4Si5, is superconducting.

The results of precise measurements of the energies of the 2p32−1s12and 2p12−1s12 muonic X-ray transitions of 92Mo, 94Mo, 95Mo, 96Mo, 97Mo, 98Mo and 100Mo are reported. The data were analyzed in terms of the Barrett moments 〈rke−αr〉 of the nuclear charge distributions from which the equivalent nuclear radii Rk and the differences ΔRk between neighboring isotopes were computed. Systematic shell effects have been observed at the neutron numbers N = 50 and N = 56.

The phase relations in the ZrRh system were reinvestigated by differential thermal analysis, levitation thermal analysis, X-ray analysis electron microprobe analysis, microstructural examinations and measurements of the superconducting transition temperatures. A new complete phase diagram is presented. Owing to the occurrence of martensitic transformations; the central part of the diagram is particularly complicated. Observed enthalpies of formation are given for three intermediate compounds.

Muonic transition energies between low-lying states in ${\ensuremath{\mu}}^{\mathrm{\ensuremath{-}}}$${\mathrm{\ensuremath{-}}}^{208}$Pb have been measured in a precision experiment using a Compton suppression spectrometer. Nuclear charge parameters and nuclear polarization corrections have been adjusted to the data. In particular, experimental correlations between the nuclear polarization corrections of the lower muonic levels have been established. A set of nuclear charge parameters reproducing all the experimental transition energies can only be obtained by assuming an inversion in magnitude of the nuclear polarization corrections not only for the 2p states, but also for the two 3p states. Such a result is unexplained by present theoretical models, but corroborates the findings of a recent experiment concerning the 2p states in ${\ensuremath{\mu}}^{\mathrm{\ensuremath{-}}}$${\mathrm{\ensuremath{-}}}^{90}$Zr. Using our best-fit parameters, a $^{208}\mathrm{Pb}$ rms radius of 〈${r}^{2}$${〉}^{1/2}$=5.5031(11) fm has been obtained.

NaI(Tl) and Ge(Li) detectors have been used singly and in a two-parameter configuration to study the gamma rays associated with the decay of 2.9-day 97Ru. Thirteen transitions have been observed and accounted for in a decay scheme involving levels at 96.4, 215.8, 324.4, 656.7, 785.1, 855.4, 969.7, and 994.4 keV. Spin and parity assignments are discussed.

Experiments using Ge(Li) and Nal(Tl) detectors singly and in a 2-parameter coincidence arrangement have been carried out to establish the role of a number of weak transitions in the decay of 143Ce. Twenty-six of the twenty-seven observed γ rays have been placed in a decay scheme with levels at 57.4, 350.6, 490.2, 721.8, 739.9, 847.9, 937.3, 1059.8, (1156.5), 1160.1, 1381.6, and 1397.4 keV. The K-conversion coefficients of the 293 and 350 keV transitions, measured with a Si(Li) detector, are 0.10 ± 02 and 0.024 ± 0.03 respectively.

Energies and intensities of muonic X-rays, nuclear γ-rays and μ-capture γ-rays were measured in natural muonic thallium with Ge(Li) detectors. The absolute intensities of higher μ X-rays were reproduced by a cascade calculation starting with a statistical population at n = 20 including K-, L- and M- conversion. The electron screening effect was deduced from energies of higher μ X-rays. Eight prompt nuclear μ-rays were found, due to an excitation of (4.1 ±1.0) % and (14.6 ± 3.0) % of the first 3 2 + level in μ 203 T1 and μ, 205 T1, respectively, and of (8.8 ± 0.9) % of the 5 2 − level at 2.63 MeV in 205 T1. This excitation explains the anomalous intensity ratios of the 2p-ls and 3d-2p fine structure components. From the nuclear y-rays of the first excited states were deduced: the magnetic h.f. splittings e 203 ( 1 2 ) = 2.57 ± 0.15 keV , e 205 ( 1 2 ) = 2.30 ± 0.02 keV, muonic isomer shifts ΔE is (203) = 0.26 ± 0.15 keV, ΔE is (205) = −(0.31 ± 0.11) keV; E2/M1 mixing ratios δ μ 2 (203) = 0.89 ± 0.27, δ μ 2 (205) = 1.00 ± 0.05, and the half-life in the presence of the muon T μ ( 3 2 ) = 1.4 ± 0.1 nsec in 205 T1. The values of e( 1 2 ) and ΔE ls were compared with shell-model calculations. From δ μ 2 and T gm ( 3 2 ) evidence for a magnetic nuclear polarization was found. From the 2p-ls, 3d-2p, 3p-2s and 2s-2p transitions the size and shape of the nuclear charge distribution and a nuclear polarization due to the 1s 1 2 muon of ΔE np = 8.3 ± 1.2 keV and 9.5 ± 1.2 keV for 203 Tl and 205 T1 respectively were determined in agreement with theoretical estimates. An isotope shift of ΔE = 10.35 ± 0.25 keV was measured for the 1s 1 2 state which is compared with data from optical spectroscopy. From an analysis of the time distribution of delayed γ-rays from μ-capture, an isotopic effect of (5.4 ± 2.5) % was found for the capture rates, in fair agreement with predictions from Primakoff's μ-capture formula.

NaI(T1) and Ge(L1) detectors have been used singly and in coincidence to study the gamma rays associated with the decay of 67 h 99 Mo Twenty-four of the twenty-eight observed transitions have been located by energy fit and by coincidence data, the remainder by energy fit alone The resulting decay scheme consists of levels at 140 5 ( 7 2 + ) , 142 6 ( 1 2 − ) , 181 1 ( 5 2 + ) 509 1 ( 3 2 − ) , 534 3, 671 5 ( 5 2 − ) , 761 6 ( 5 2 + ) , 920 5 ( 3 2 + , 1 2 + ) , 1004 0 ( 3 2 − ) , 1072 9 ( 5 2 − ) , 1129 3 ( 1 2 − , 3 2 − ) , 1142 0 3 2 − ) , 1199 ( 1 2 − , 3 2 − )

The following conversion ratios of the 191 keV transition in 197Au have been measured with a double focussing β-spectrometer: K/L = 5.9±0.2, LI/LII = 10.7±0.5, LI/LIII = 74±15. The LI/LII value is consistent witg a practically pure M1 transition (E0(LI)/M1 ≦0.9% orE2/M1 ≦ 0.6%). which leads to a calculated αK = 1.01±0.03. The LI/lIII value corresponds to a mixture E2M1 = (0.9−0.5+0.7)% giving αK = 0.983±0.005. The two derived αK agree with each other. Their values exclude reported αK which give strong E0 admixtures and spin 1 2 + of the 269 keV level. Some other αK measurements and the theoretical value (core-particle model) are in good agreement with our result and give a strong preference for spin 3 2 + of the 197Au 269 keV level.

Es wird eine Anordnung zur Erzeugung monochromatischer (d,d)-Neutronen beschrieben. Sie beruht auf einer Koinzidenzmethode, bei der als Koinzidenzpartner die in der (d,d)-Reaktion gleichzeitig entstehenden He3-Kerne und Neutronen benützt werden. In der angeführten Anordnung werden die He3-Kerne unter 90° zum einfallenden Deuteronenstrahl beobachtet. Als Target wird ein D2-Gastarget benutzt. Die berechnete Energiebreite der Neutronen für die gewählte Anordnung beträgt ca. 10 keV. Für eine Deuteronenenergie von 900 keV und 5 μA Stromstärke ergeben sich ca. l Koinzidenzimpuls pro Sekunde. Es sollte möglich sein, diese Zahl durch Vergrößerung des benutzten Neutronenzählers um einen Faktor 10 zu erhöhen, ohne das Energieauflösungsvermögen zu verschlechtern. Die Zahl der zufälligen Koinzidenzen variiert zwischen 5 — 10% der wahren Koinzidenzen.

A special construction of a double focusing iron β-spectrometer, with a normal radius of 30 cm, was designed, which can be taken as a combination of the two classical models, namely the core-in-the-center and the inside-out type, with subdivided induction coils. The advantage of this construction is that the field shape produced can be varied by changing the ratios of the currents in the separate sub-coils, so that it may be made to fit the theoretical proposal better than the one produced by a simple iron joke. Furthermore, it may be reasonably expected that the fringing effect would be smaller in such a construction than in the usual design. Construction details, such as the form of pole surfaces, coil dimensions, baffle shape, detector and source arrangements, current supply and field stabilisation are described. With the aid of Hall plate measurements, the field shape was made to fit as well as possible to the theoretical curve, given by H Z ( ϱ ) = H 0 (1−0.5 ϱ + 0.375 ϱ 2 −0.299 ϱ ). Finer adjustments were carried out, using different performance criteria, which respond more sensibly to the changes of field shape. With the optimum field chosen, combinations of initial conditions were studied experimentally and compared with the theoretical prediction, with a view to obtain maximum luminosity for a given resolution. At an impulse resolution setting of 0.1%, a source of 1 × 20 mm 2 and a solid angle of 0.5% can be used. The highest resolution as yet achieved is 3.6 × 10 −4 with a source of 0.2 mm width.

Electric quadrupole X-ray transitions (5g → 3d, 4f → 2p, and 3d → 1s) have been observed in muonic Tl, Pb and Bi. From the 3 → 1 transitions, energy splittings of the n = 3 levels were deduced. From a comparison of the relative intensities of E1 and E2 transitions, the population ratios 5g 5f , 4f 4d , and 3d 3p were deduced. These ratios are well reproduced by a cascade calculation assuming a statistical initial population at n = 20, including K, L and M shell conversion. In the case of 205 T1 discrepancies between the experimental and the calculated 3d-1s/3p-1s intensity ratio can be explained by nuclear excitation. From the 3 p 3 2 → 1 s 1 2 intensity in 209 Bi we can deduce the ratio of the radiationless to the X-ray transition width and give limits for prompt neutron emission from the 3d level.

The muonic x-ray intensities of the Lyman series in pure silicon are investigated. The fitted data are compatible with a statistical initial angular momentum distribution of the captured muons. From a comparison with data measured in diamond, cubic boron nitride and in the two isoelectronic series F/sup -/,Ne,Na/sup +/ and Cl/sup -/,Ar,K/sup +/, we conclude that the calculated muon distribution reflects the symmetry of the electrons through which muon capture proceeds.

Measurements of relative Coulomb capture rates of muons in compounds of nitrogen, sulphur and selenium have been performed. The obtained results may be interpreted as showing a valence state dependence

Lyman series of muonic nitrogen have been measured in BN, NaNO 2 and NaNO 3 . Changes seen in the muonic X-ray intensity structures and the capture ratios may be attributed to the variation of the electron density in the valence shells.

The scientific program and the experimental setup of the DEAR (DAΦNE Exotic Atom Research) experiment at the new φ-factory DAΦNE of Laboratori Nazionali di Frascati are described. The objective of DEAR is to perform a 1% measurement of the Kα line shift due to the strong interaction in kaonic hydrogen. A measurement will also be performed on kaonic deuterium for the first time. The aim is to investigate low-energy \(\overline K N\) physics and to understand SU(3) chiral symmetry breaking. The setup takes advantage of the unique features of the “kaon beam” from the φ decay in DAΦNE; of a low-temperature pressurized gaseous target; and of a detector for soft X-rays – the Charge-Coupled Device (CCD) – characterized by a very good energy (and spatial) resolution and by an unprecedented background rejection capability. The DEAR experiment represents a major effort in the study of low energy \(\overline K N\) interactions and has the potential to produce a breakthrough in the field.

In muonic 190,192Os the magnetic hf-spliting of the 2+ → 0+ nuclear transition was measured. The hf-splittings ΔE( 190 Os ) = 665 ± 80 eV and ΔE( 192 Os ) = 800 ± 80 eV of the 2+ state are reduced at 59% compared to a point-like magnetic moment in agreement with the assumption of a magnetization density of a magnetization density distribution proportional to R2 ϱcharge(R) as calculated from a rigid rotator. The influence of these results on the analysis of muonic isomer shifts is pointed out.

Energies of the 5g-4f muonic X-rays have been measured in nat Hg and 203 Tl with an accuracy of about 25 eV. They are found to be smaller than theoretical energies including recently revised calculations of higher-order vacuum polarization, by about two standard deviations.

The X-ray spectrum of pionic 208 Pb has been measured. The deduced values of the strong interaction monopole shift with respect to the point Coulomb energy are ϵ 0 (4f) = 1.49±0.02 keV and ϵ 0 (3d) = 19.4±1.2 keV. The observed s strong interaction absorption widths of this spherical nucleus are found to be Γ 0 (4f) = 1.25±0.02 keV and Γ 0 (3d) = 47.0±3.6 keV. Important in the analysis of the pionic 4f level is the intensity balance for this level, giving an additional check on the measured absorption width of the pionic 4f level. For the more peripheral 4f state the measured strong interaction shifts and widths are well explained by standard optical model calculations. The values for the 3d state, however, are not in agreement with these calculations.