g-Faktoren und Multipol-Mischungsverhältnisse in156Gd

By integral perturbedγ-γ-angular correlation the gyromagnetic ratios of a 2-quasi-particle state at 1,513 keV and the 4⁺ state of the ground state rotational band in¹⁵⁶Gd were measured, using sources prepared by¹⁵⁹Tb(γ, 3n) and¹⁵⁶Gd(d, 2n) reactions:g _{1;513 keV} ⁴⁺ =0.78±0.05;g _R ⁴⁺ =0.37±0.05. In addition we obtain the multipole mixing ratiosδ _{535 keV}(M2/E1)=?0.09±0.01;δ _{1,225 keV}(E2/M1)=+1.83±0.10 for the 535 keV and 1,225 keVγ-rays. The classification of the 1,513 keV state is discussed. The internal field of Gd in Tb metal at 77 °K was found to beH=(?192±16)kOe.     

Reinvestigation of the decay scheme of the short-lived isomeric states in112In

The two short-lived isomeric states in¹¹²In have been reinvestigated by means of the¹¹²Cd(d, 2n) and¹⁰⁹Ag (α, n) reactions. Measurements of delayed X- andγ-ray, lifetime and TDPAD spectra have been performed. A 6.32(3) keVγ-ray has been identified in the isomeric decay and anM1 multipolarity has been assigned to it on the basis of the measured internal conversion coefficients:α _L =196(39) andα _tot=231(35). TheE1+M2(δ =+0.24(4)) andE2 multipolarities have been determined for the 263 and 188 keV transitions deexciting the 8^?(T _1/2=2.82(2) μs) and 7⁺ (T _1/2=0.93(2) μs) isomeric states, respectively. A revised isomeric decay scheme is presented.     

Internal conversion studies of the 114 keV transition in175Lu

Measurements of the conversion line intensities, the directional correlation and the conversion probability for the 114 keVM1+E2 transition in¹⁷⁵Lu are reported. TheE2 admixture, determined from relativeK andL intensities, is (19.2±0.2)%. The theoreticalL _I internal conversion coefficient is found to be about 8% too low relative theK,L _II andL _III conversion coefficients.     

Internal conversion coefficients and penetration effect for the 279 keV transition in203Tl

The internal conversion process of theM1+E 2 mixed 279 keVγ-ray transition in the decay of²⁰³Hg has been reinvestigated. The emission rate of theK-shell internal conversion electrons was determined with an electron X-ray coincidence measurement using a magneticΒ-spectrometer and a Si(Li) detector of high energy resolution. Conversion electron ratios were obtained from electron spectra recorded as a function of momentum. The disintegration rate has been taken from measurements with a calibrated NaI(Tl)γ-ray spectrometer. Following results have been deduced: α=0.2279±0.0024, α _K =0.1653±0.0017, α _L =0.0475±0.0013,K/(L+M+?)=2.64±0.03,K/L=3.48±0.12,L/(M+N+ ?)=3.14±0.12. On the basis of the experimental results on theK-shell internal conversion coefficient,α _k , and the conversion ratioK/(L+M+?) the penetration effect on the internal conversion of theM1 part and the mixing ratio,δ ², of the 279 keVγ-ray transition in²⁰³Tl have been studied. Calculations were made using Hager and Seltzer's formalism and their theoretical internal conversion coefficients. The results are consistent with a mixing ratio ofδ ²=1.32±0.11 and a penetration parameter ofλ=6.8 ±0.8.     

Relative internal conversion electron intensities of the 113 keV transition in177Hf

The intensities of the internal conversion lines of the 113 keVM1 +E2 transition in¹⁷⁷Hf have been measured. From comparison with theoretical conversion coefficients the transition has been found to be (95.2 ± 0.5)%E2 corresponding to ¦δ¦=4.5 ± 0.3. The theoreticalL _I andM _I conversion coefficients used in the comparison have been increased by 5% according to the result that for pureE2 transitions in the deformed region theL _I/L _II,L _I/L _III,M _I/M _II, andM _I/M _III theoretical ratios are too low (～5%). Moreover, the present result indicates that theL _II/L _III andM _II/M _III ratios obtained from the tabulations by Hager and Seltzer and from the computer program by Pauli are too high (1–2%).     

Strengths of (p, γ) resonances in 33Cl, 35Cl and 28Si

Absolute strength measurements have been performed for the E_p = 580 and 588 keV ³²S(p,γ)³³Cl, E_p = 1214keV³⁴S(p,γ)³⁵Cl and E_p = 633 and 744 keV²⁷Al(p,γ)²⁸Si resonances with a Ge(Li) detector. Results are discussed with regard to the decay of isobaric analog resonances in ³⁵Cl and ³⁷Cl.     

Mesures des vies moyennes des niveaux de 1K alimentes par les réactions 39K(t,p) et 27Al(16O, 2p)

Twenty-four levels in ⁴¹K at excitation energies below 5 MeV have been identified in the reactions ³⁹K(t, p)⁴¹K and ²⁷Al(¹⁶O, 2p)⁴¹K, at incident beam energies of 3.0 and 34 MeV respectively. Using the recoil-distance technique and the Doppler-shift attenuation method, mean lifetimes (in ps) were obtained for the following levels: 980 keV, 0.42^0.30_0.15; 1294 keV, > 5; 1560 keV, 0.58 ± 0.22; 1582 keV,> 1.5; 1677 keV, 6⁺³_?1; 1698 keV, 1.3 ± 0.4; 2528 keV, 230 ± 15; 2762 keV, < 2; 2775 keV, 68 ± 4; 4274 keV, < 2; 4983 keV, 95 ± 15. The positive parity states are suggested to have predominantly 2p-1h configurations. As a by-product, mean lifetimes for five levels in ⁴¹Ca, populated via the ²⁷Al(¹⁶O, pn)⁴¹Ca reaction, were also obtained.     

RS model with a small curvature and dielectron production at the LHC

In the framework of the Randall-Sundrum-like scenario with the small curvature κ (RSSC model), p _⊥-distributions for the dielectron production at the LHC are calculated. For the summary statistics taken at 7 TeV (L = 5 fb^?1) and 8 TeV (L = 20 fb^?1), the exclusion limit on the 5-dimensional gravity scale M ₅ is found to be 6.35 TeV at 95% C.L. For √s = 13 TeV and integrated luminosity 30 fb^?1, the LHC search limit is estimated to be 8.95 TeV. These limits on M ₅ are independent of κ, provided the relation κ ? M ₅ is satisfied.     

Weak-coupling expansion of the low-lying energy values in the SU(2) gauge theory on a torus

Relying on analytic results obtained previously, we complete the one-loop computation of the low-lying energy values of the SU(2) gauge theory in an L × L × L periodic box. The expansions are then rewritten in terms of the universal parameter z = M(0⁺) · L (M(0⁺): energy gap in the J^p = 0⁺ sector). We find that the crossover from small-volume to large-volume behaviour is likely to take place at z ? 2. Furthermore, near the crossover, the lowest energy levels (above the ground state) in the 0⁺ sector and the 2⁺ sector are practically degenerate. In each of these sectors there is one more state at about 1.5 · M(0⁺). In the 0^? sector, on the other hand, the lowest energy value is greater than 3 · M(0⁺).     

4f ground state properties of cerium in AuCu3 intermetallic compounds studied by x-ray absorption spectroscopy

L_III absorption edges of cerium in ternary AuCu₃ compounds Ce(Pd_1?xM_x)₃ (M = Ag and Rh) and (Ce_1?xY_x)Pd₃ are presented. We find that Ce in these compounds is mixed valent with n_f ? 0.7. The valence V of Ce(Pd_1?xRh_x)₃ becomes concentration independent of V = 3.29 ± 0.02 for x ? 0.18. In Ce_1?xY_xPd₃ we observe the valence to increase up to V = 3.32 ± 0.02 at the highest concentration of Y. We show, that a critical volume, available for the Ce atom, is associated with the concentration independent valence around 3.3. For both systems, linewidths W₁, W₀ and Δ = E(4f¹) ? E(4f⁰), as derived from L_III double-bump structure, are given. Possible falsifications due to “final states effects” on the valence are discussed.     

Scattering of low energy Na+ ions from a clean polycrystalline Ag surface

The energy distributions of low energy (E₀ = 0.4–3.2 keV) Na⁺ ions scattered from a clean polycrystalline Ag surface were measured. The angle between the incident beam and the surface was fixed at ψ = 45° while the scattering angle (θ) ranged from 50 to 130°. The cleanliness of the surface during the measurement was maintained by simultaneous deposition of Ag atoms from an effusion source. The obtained distributions considerably differ from the corresponding distributions of noble ions. Firstly, for all measured values of E₀ and θ, an intensive hump is observed in the high energy part of the distribution. In certain cases this hump is transformed into a peak. Secondly, the low energy part of the distribution is very pronounced, especially for higher values of E₀ and θ.     

Local coordination of Co2+ and Ni2+ cations in polyacrylate matrices

Parameters of the local coordination of Co²⁺ and Ni²⁺ cations in polymer matrices are determined by XAFS spectroscopy at the K edges of the corresponding elements. Ion-exchange complexes of Ni²⁺ and polymethacrylate, low-molecular acrylamide complexes [M(CH₂=CHC(O)NH₂)₆](NO₃)₂ (M = Co or Ni), and products of their thermal polymerization are investigated. The final results are in agreement with the octahedral coordination of M atoms (average distances, 2.10–2.11 (Co-O) and 2.05–2.06 Å (Ni-O).     

Many-body effects in l2mm auger electron spectra of Ge(CH3)4 excited by Mg Kα X-rays

The Ge:L₂MM Auger electron spectra excited by Mg Kα X-rays from Ge(CH₃)₄ free molecules have been compared with the corresponding spectra excited by Al Kα X-rays. The Al Kα excited spectra have characteristic features of the diagram Auger transitions, because the excitation energy is far above the L₂ ionization threshold. The energy of Mg Kα photons is 1.21 eV below the Ge:L₂ ionization threshold and thus the Mg Kα excited L₂MM Auger electron spectra indicate many-body effects, post collision interaction (PCI) effects and spectator Auger satellite structures. The L₂M_4,5M_4,5 type spectrum displays both these features but the L₂M_2,3M_4,5 type spectrum has only a spectator Auger satellite structure, because the (3p⁻¹3d⁻¹nl) final state interferes with the (3s) hole state.     

Search for a 11/2−→3/2+ M 4 transition in141Sm

The electromagnetic decay of the 11/2^{? 141m} Sm is investigated. Internal conversion electron and X-ray-conversion electron coincidence measurements indicate that the state undergoesβ ⁺ and electron capture decay with 99.69% strength and the remaining 0.31% goes to a 174.2±0.3 keVM4 transition. TheK/L conversion electron intensity ratio for the transition is measured to be 1.7±0.4. The energy of the 11/2^? is established at 175.8±0.3 keV above the 1/2⁺ ground state in¹⁴¹Sm. Systematics of theM4 transitions in theN=79 and 81 isotones are discussed.     

First-principles study of the sulfur K and L2,3 edges of transition metal disulfide monolayers,MS2 (M=Mo,W and Re)

By means of the energy loss near edge structure (ELNES) analysis, the electronic structures of layered transition metal disulfides were studied. In the framework of full potential linearized augmented plane wave method, ELNES spectra of sulfur K and L_2,3 edges of layered MoS₂, WS₂ and ReS₂ have been calculated at magic angle conditions, and compared with those of bulks and the only existing experimental fine structure. Compared to the bulks, the energy differences between the main peaks in sulfur K and L_2,3 edges of monolayers decrease due to the slightly larger bond lengths that it can be used as a fingerprint for monolayers. Sulfur K edges in monolayers include some main features originated from electron transition to p_z (π) and p_x+p_y (σ) states and their hybridization. The overall dispersions of the sulfur L_2,3 edges in all cases are similar to the d-symmetry density of states. The first two features in L_2,3 edge of bulks and monolayers can be attributed to electron transition of sulfur 2p to the both unoccupied 3s-like states of sulfur and 4d states of transition metal atoms. Due to the considerable amount of s states at the energy position of a shoulder like structure in L_2,3 edge of both bulks and monolayers, these structures can be assigned to the sulfur 2p electron transition to unoccupied sulfur 3s states. The other features at higher energies are due to the transition of sulfur 2p electrons to the d-symmetry states of sulfur. In addition, due to the considerable energy band gaps, it seems that the use of core–hole approximation is essential for accurate reproduction of ELNES features of transition metal disulfides.     

Noncollinear phase matched four photon frequency mixing in water

An intense ultraviolet picosecond light pulse at ω_S = 2γ_P ? ω_L is generated in water by noncollinear phase matched nonresonant four photon frequency mixing of two input picosecond light pulses at frequencies ν~_P = 18 960 cm^-1 and ν~_L = 9480 cm^-1. An energy conversion of up to W_S/W_L = 0.07 was achieved. The nonlinear susceptibility components were determined to be χ⁽³⁾_yyyy(?ω_S; ω_P, ω_P, ? ω_L) = 7.5 × 10^-34 Cm/V³ and χ⁽³⁾_yxxy(?ω_S; ω_P, ω_P, ?ω_L) = 2.4 × 10^-34 Cm/V³.     

Internal energy of AB2X4 crystalline compounds. Electrostatic energy contribution for compounds with closed shell cations

Madelung energy calculations are performed for two different lattices in which some of AB₂X₄ compounds (A = M⁺², B = M^?3, X = O^?2, S^?2, Se^?2, Te^?2) crystalline.A gross evaluation of the covalent bond energy contribution in the same crystals is made and some considerations are draw from the comparison between the two above quoted energy contributions.     

Percolation on the square lattice in aL×M geometry

A study of the site percolation model on the square lattice in aL×M geometry at critically is presented. ForL?M one observes the growth of numerous percolation colation clusters in theL-direction in contrast to the absence of percolation in theM-direction. Consequently, relevant properties of these clusters such us for example the average number of clusters (N _CL ), the cluster length distribution (P(l,L), withl=cluster length in theM direction) and average cluster length (l _CL ), are studied by means of the Monte Carlo technique and analyzed on the basis of finite-size scaling arguments. The following behavior is found:N _CL ?(3/8) (L/M)^?δ, with δ=1; andl _CL ?2.0L. Also the distributionP(l, L) is of the exponential-exponential type and their characteristic exponents are evaluated.     

Interference effects in 12C(p, γ)13N and direct capture to unbound states

Excitation functions of the capture reaction ¹²C(p, γ₀)¹³N have been obtained at θ_γ = 0° and 90° and E_p = 150–2500 keV. The results can be explained if a direct radiative capture process, E1(s and d → p), to the ground state in ¹³N is included in the analysis in addition to the two well-known resonances in this beam energy range $\text{[E}{}_{\mathrm{p}}\text{= 457(}\text{1}\text{2}{}^{\mathrm{+}}\text{)}$ and 1699 $\text{(}\text{3}\text{2}{}^{\mathrm{?}}\text{) keV]}$. The direct capture component is enhanced through interference effects with the two resonance amplitudes. From the observed direct capture cross section, a spectroscopic factor of C²S(l = 1) = 0.49 ± 0.15 has been deduced for the $\text{1}\text{2}{}^{\mathrm{?}}$ ground state in ¹³N. Excitation functions for the reaction ${}^{12}\text{C(p,γ}{}_1\text{p}{}^1\text{)}{}^{12}\text{C}$ have been obtained at θ_γ = 0° and 90° and E_p = 610–2700 keV. Away from the 1699 keV resonance the capture γ-ray yield is dominated by the direct capture process E1 (p → s) to the $\text{2366 (}\text{1}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound state. Above E_p = 1 MeV, the observed excitation functions are well reproduced by the direct capture theory to unbound states (bremsstrahlung theory). Below E_p = 1 MeV, i.e., E_p → 457 keV, the theory diverges in contrast to observation. This discrepancy is well known in bremsstrahlung theory as the “infrared problem”. From the observed direct capture cross sections at $\text{E}{}_{\mathrm{p}}\text{? 1 MeV}$, a spectroscopic factor of C²S(l = 0) = 1.02 ± 0.15 has been found for the $\text{2366 (}\text{1}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound state. A search for direct capture transitions to the $\text{3512 (}\text{3}\text{2}{}^{\mathrm{?}}\text{)}$and $\text{3547 (}\text{5}\text{2}{}^{\mathrm{+}}\text{) keV}$ unbound states resulted in upper limits of C²S(l = 1) ≦ 0.5 and C²S(l = 2) ? 1.0, respectively. The results are compared with available stripping data as well as shell-model calculations. The astrophysical aspect of the ¹²C(p, γ₀)¹³N reaction also is discussed.