Search

The optimum yield-scaled global warming potential (GWP) of perennial crops on arid land requires effective strategies for irrigation and fertilization. In 2009–2010, N2O emissions and CH4 oxidation were measured from an almond [Prunus dulcis (Mill.) D.A. Webb] production system irrigated with nitrogen (N) fertilizers. Individual plots were selected within a randomized complete block design with fertilizer treatments of urea ammonium nitrate (UAN) and calcium ammonium nitrate (CAN). Event-related N2O emissions from irrigation and fertilization were determined for seasonal periods of post-harvest, winter, spring and summer. Peak N2O emissions in summer occurred within 24 h after fertilization, and were significantly greater from UAN compared to CAN (p

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.

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 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.

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 %.

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.

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.

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.

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.

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 superconducting transition temperatures of compounds RE5Os4Si15 have been measured as a function of hydrostatic pressure up to 1.4 GPa. Transition temperatures decrease linearly, with pressure coefficients ranging from 0.6 to 1.1 K/GPa. Across the series, the variation of Tc due to the change in unit cell volume and the effect of magnetic pairbreaking are of similar magnitude but opposite sign. We obtain a characteristic product N(EF)I2 = 2· 10−4eV which is approximately twice the value obtained when volume effects are neglected.