NMR relaxation of 7Li in concentrated lithium-ammonia solutions

The Knight shift and the spin-lattice relaxation time of ⁷Li in lithium-ammonia solutions have been measured at -57°C over the concentration range X_Li = 0.01–0.20 (X_Li: mole fraction of Li). The Knight shift increases with increasing metal concentration, while the relaxation rate, 1/T₁, shows a broad minimum around X_Li = 0.07.     

Resonant cross-relaxation between Cr3+ and V3+ in Al2O3

Cross-relaxation, which occurs when a V³⁺ transition is resonant with a monitored Cr³⁺ transition, leads to a marked reduction of the spin-lattice relaxation time of Cr³⁺ in Al₂O₃. Measurements and an analysis of the temperature dependence of this effect give a value of 8.34 ± 0.49 cm^?1 for the zero-field splitting of V³⁺, an ion which is strongly coupled to the lattice.     

The mass and low-lying levels of 40Cl

The mass excess of the T_z = 3 nucleus ⁴⁰Cl has been determined using the ⁴⁰Ar(⁷Li, ⁷Be)⁴⁰Cl reaction. A value ?27.527 ± 0.035 MeV was obtained. A number of excited states of ⁴⁰Cl were a1so observed. In addition, the ⁴⁰Ar(¹¹B, ¹¹C)⁴⁰Cl and ⁴⁰Ar(¹¹B, ¹³N)³⁸S reactions were investigated. Excited states of ³⁸S were observed at 1.28 ± 0.04 and 3.38 ± 0.10 MeV.     

嵌段共聚物溶致液晶相中水的2H-NMR动力学分析

采用D₂O 的²H-NMR线型和弛豫分析了PEO-PPO-PEO/D₂O/对二甲苯体系的层状和六角液晶相的动力学行为. 通过实验测得了两个不同体系的自旋 晶格弛豫时间T₁、自旋-自旋弛豫时间T₂和²H-NMR 谱. ²H-NMR 谱均为具有四极劈裂的粉末谱线型，且在谱图的中心，β_LD=54.7°时存在一个倒峰. 倒峰的出现直接表明引起体系中弛豫的主要动力学过程处于极窄化区域. 采用NMR弛豫模型，通过调节动力学参数，使理论模拟的²H-NMR谱、弛豫时间、倒峰的大小与实验的对应量相吻合，求得了体系的动力学参数.     

Covalent distribution of spin in V2O3:O17 nuclear resonance

O¹⁷ nuclear magnetic resonance has been observed in metallic V₂O₃ with frequency shifts from (?0.10 ± 0.02)-(?0.05 ± 0.02) per cent between 170 and 460°K respectively, a linewidth of 37 ± 5 oe and spin-lattice relaxation rate 1/T₁ ≈ 60 sec^?1 at 296°K. From these quantities, covalency parameters f_s/2S = ? 0.35 × 10^?3 and ?_π/2S ≈ ? 0.07 are calculated. One of the two vanadium 3d electrons in the antiferromagnetic state below the 170°K metal-insulator transition is inferred to lie in a non-magnetic state, while covalent charge transfer augments the spin moment of the other 3d electron to the observed 1.2 μ_B.     

Co2+ spin-lattice relaxation narrowing of 19F NMR in KCoF3

The temperature dependence of the ¹⁹F NMR linewidth ΔH in KCoF₃ has been measured over the entire paramagnetic solid state region. The dramatic decrease in the hyperfine-broadened, exchange narrowed ΔH that occurs above 200 K is interpreted as arising from fast Co²⁺ single-ion, spin-lattice relaxation. A model theory of the temperature dependence of ΔH is given which incorporates the interplay of exchange and spin lattice relaxation effects on the decay of the spin autocorrelation function.     

Precise measurement of magnetic moment of short-lived β-emitting nuclei12B ( I π=1+, T 1/2=20.18 ms)

The spin polarized β-emitting nuclei¹²B (I ^π=1⁺,T _1/2=20.18 ms) were produced by the nuclear reaction¹¹B(d, p)¹²B and by the selection technique of the incident deuteron energy and the¹²B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei¹²B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment of¹²B was determined to be μ=0.99993±0.00048 nm org=0.99993±0.00048 after the precise correction of the Knight shift.     

Reactions of 40Ar with 159Tb, 142Nd and 144Sm; New α-activities from 189Bi, 173Pt and 177Au

Reactions of ⁴⁰Ar ions with targets of ¹⁵⁹Tb, ¹⁴²Nd, and ¹⁴⁴Sm have been studied at energies below 300 MeV with a helium gas-jet system. Excitation functions for (Ar, xn) reactions, where x = 5–10, were obtained for the radioactive products that decay by α-emission. Based on the characteristics of these excitation functions and on the systematics of α-decay, evidence is presented for the existence of the nuclides ¹⁸⁹Bi with α-particle energy E_α = 6.67±0.01 MeV and half-life < 1.5 sec, and ¹⁷³Pt with E_α = 6.19±0.01 MeV; and for the emission from ¹⁷⁷Au of an α-particle with E_α = 6.15±0.01 MeV.     

Lifetimes of some excited states in 64Ni, 66Zn and 68Zn

Mean lives and excitation energies of the lowest levels in⁶⁴Ni,⁶⁶Zn and⁶⁸Zn were measured with the aid of the (α, α′γ) and (α, pγ) reactions. The γ-rays were detected in coincidence with the outgoing particles. The following mean lives were determined from DSA measurements: 400 ± 150 fs for the level at E_x = 1.35 MeV in ⁶⁴Ni; 270 ± 100, 210 ± 110, 330 ± 200, 80 ± 70 fs for the levels at E_x = 1.87, 2.45, 2.83, 2.94 MeV in ⁶⁶Zn, and 1300 ± 300, > 160, 600 ± 200 fs for the levels at E_x = 1.08, 1.89 and 2.76 MeV in ⁶⁸Zn, respectively.     

Electromagnetic transition strengths in 24Na

Mean lifetimes, excitation energies and branching ratios of ²⁴Na states, populated in the ²³Na(d, p)²⁴Na reaction have been measured. Gamma-ray spectra were measured at three angles in coincidence with proton groups at θ_p = 169°. Mean lifetimes obtained from DSA are (excitation energy in keV, lifetime in fs): 563, > 1000; 1341, 95 ± 30; 1344, 38 ± 11; 1346, > 1500; 1512, 38 ± 11; 1846, 260 ± 50; 1885, 36 ± 9; 2513, 15 ± 7; 2563, < 25; 2904, 50 ± 15; 2978, < 25; 3216, 22 ± 8; 3372, 19 ± 5. For higher levels up to 4207 keV upper limits of 30 fs were set. In combination with earlier work the following unique spin(-parity) assignments could be made: J^π(1846) = 2⁺, J(2513) = 3, J^π(3745) = 3^?. A new level at E_x = 3681.7 ± 0.6 keV is reported.     

Cs nuclear magnetic resonance study in CsZnCl3 single crystals of perovskite ABX3 type

CsZnCl₃ single crystals were grown by the slow evaporation method, and the spin-lattice relaxation rates and resonance lines of the ¹³³Cs nuclei in the resulting crystals were investigated using FT NMR spectrometry. The temperature dependence of the relaxation rate of the ¹³³Cs nuclei in the CsZnCl₃ crystals was found to be continuous near T_C (=366 K), and was not affected by this phase transition. Our results for CsZnCl₃ are compared with those obtained previously for other CsBCl₃ (B=Mn, Cu, and Cd) perovskite crystals. The Cs relaxation time of CsCdCl₃ is longer than that of CsMnCl₃. The differences between the atomic weights of Mn, Cu, Zn, and Cd are responsible for the differences between the spin-lattice relaxation times of these single crystals. The influence of paramagnetic ions is also important in these crystals. The differences between the spin-lattice relaxation times of these crystals could also be due to differences between the electron structures of their metal ions, in particular the structures of the d electrons.     

Investigation of TmFe4Al8 and DyFe4Al8 by means of 169Tm and 161Dy Mössbauer spectroscopy

We have performed ¹⁶⁹Tm and ¹⁶¹Dy Mössbauer spectroscopy on TmFe₄Al₈ and DyFe₄Al₈. From the temperature dependence of the electric quadrupole splitting of the ¹⁶⁹Tm spectra of TmFe₄Al₈ we have determined the second order crystal field potential V⁰₂ = (100 ± 10) K and the exchange field term g_Jμ_BH_M = (1 ± 1) K. The temperature dependence of the hyperfine field of the ¹⁶¹Dy spectrum of DyFe₄Al₈ gives g_Jμ_BH_M = (15 ± 3) K. With these exchange fields magnetic transition temperatures of the rare earth sublattices were found, which are consistent with experiment. The relaxation behaviour of the Tm sublattice below T_N = 187 K is discussed.     

7 MeV dipole ground state transitions in 207Pb, 208Pb and 209Bi

The Doppler-broadened 7.117 MeV line from the ¹⁹F(p, αγ)¹⁶O reaction has been used to resonantly excite levels in ²⁰⁸Pb at 7071±2 and 7091±2 keV, in ²⁰⁷Pb at 7186±5 and 7206±5 keV and in ²⁰⁹Bi at 7179±5 and 7202±5 keV. On the basis of angular distribution measurements the 7071 and 7091 keV levels of ²⁰⁸Pb are assigned spins of 1 and assuming 100% ground state branching the widths are calculated to be 31±3 and 17±2 eV respectively. It is suggested that the states in ²⁰⁷Pb and ²⁰⁹Bi arise from the weak coupling of a $\text{P}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ neutron hole and an $\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ proton respectively to one or the other of the ²⁰⁸Pb levels. The widths obtained in terms of _gΓ_o²/Γ are 15±4 and 25±5 eV for the 7186 and 7206 keV levels of ²⁰⁷Pb and 24±5 and 30±5 for the levels of ²⁰⁹Bi respectively. These values are consistent with the weak-coupling suggestion.     

Investigation of the 3.46 MeV isomeric level of 38K with the 24Mg(16O,pnγ)38K reaction

The τ_{$\text{1}\text{2}$} = 22 μs isomeric level of ³⁸K at an excitation energy of 3458.0 ± 0.2keVf is strongly populated in the ²⁴Mg(¹⁶O, pnγ)³⁸K reaction. Delayed γ-rays are studied with Ge(Li), Si(Li), and NaI detectors. Accurate excitation energies, branching ratios and lifetimes of levels involved in the decay of the isomeric state are determined. The isomeric level predominantly decays by a dipole transition of 38.03±0.03 keV with a total conversion coefficient of α_T = 0.42 ± 0.15. Mean lives of ³⁸K levels are measured with the recoil-distance method. The results are τ_m = 10.1 ± 0.9 ps, 1.41 ± 0.14 ns and 101 ± 15 ps for the levels at excitation energies of 0.46, 2.65 and 3.42 MeV, respectively. It is suggested that the (1f_{$\text{7}\text{2}$})² structure of a low-lying J^π = 7⁺ state in combination with the selection rules for γ-decay in a self-conjugate nucleus is responsible for the isomerism.     

Search for direct CP violating charge asymmetries in K±→π±π+π- and K±→π±π0π0 decays

A measurement of the direct CP violating charge asymmetries of the Dalitz plot linear slopes A_g=(g⁺-g^-)/(g⁺+g^-) in K^±→π^±π⁺π^- and K^±→π^±π⁰π⁰ decays by the NA48/2 experiment at CERN SPS is presented. A new technique of asymmetry measurement involving simultaneous K⁺ and K^- beams and a large data sample collected allowed a result of an unprecedented precision. The charge asymmetries were measured to be A^c _g=(-1.5±2.2)×10^-4 with 3.11×10⁹K^±→π^±π⁺π^- decays, and Aⁿ _g=(1.8±1.8)×10^-4 with 9.13×10⁷K^±→π^±π⁰π⁰ decays. The precision of the results is limited mainly by the size of the data sample.     

Reorientation effect measurements in 124Te, 126Te and 128Te

Coulomb excitation probabilities of the first 2⁺ states of ¹²⁴Te, ¹²⁶Te and ¹²⁸Te have been determined. The measurement was performed by resolving the inelastically and elastically backward scattered ⁴He and ¹⁶O projectiles using an annular surface barrier detector. Quadrupole moments (Q₂₊) as well as the B(E2, 0⁺ → 2⁺) values were extracted by analyzing the excitation probabilities with the Winther-de Boer multiple Coulomb excitation program. The Q₂ deduced for the positive sign of the 2⁺ interference term are ?0.41 ± 0.08 e · b, ?0.144 ± 0.11 e · b and ?0.12 ± 0.09 e · b for ¹²⁴Te, ¹²⁶Te and ¹²⁸Te, respectively.     

Masses and level schemes of 33Si and 34Si

The mass excesses of ³³Si and ³⁴Si have been measured using the ³⁶S(¹¹B, ^{14, 13}N)^{33, 34}Si; reactions. Values of $\text{?20.550 ± 0.030}\text{MeV}\text{(}{}^{33}\text{Si) and ?20.017 ± 0.025}\text{MeV}\text{(}{}^{34}\text{Si)}$ were obtained. In addition, an excited state of ³⁴Si was observed at 5.33 ± 0.05 MeV, and excited levels of ³³Si were observed at 1.06 ± 0.02 and 4.32 ± 0.03 MeV. These results are compared with recent shell-model calculations.     

Proton radii determinations from the ratio of π+ elastic scattering from 11B and 12C

A new method using low energy π⁺ elastic scattering is employed to determine the proton matter distribution of a nucleus relative to an adjacent nucleus differing by one proton. The difference in the rms charge radii of ¹²C and ¹¹B was determined to be 0.072 ± 0.021 fm with π⁺ beam energies of 38.6 and 47.7 MeV.     

A study of molecular motion and Raman processes in K3H(SO4)2 and KHSO4 single crystals by observation of H and K spin-lattice relaxation

The spin-lattice relaxation rates for ¹H and ³⁹K nuclei in K₃H(SO₄)₂ and KHSO₄ single crystals, which are potential candidate materials for use in fuel cells, were determined as a function of temperature. The spin-lattice relaxation recovery of ¹H can be represented for both crystals with a single exponential function, but cannot be represented by the Bloembergen-Purcell-Pound (BPP) function, so is not related to HSO₄ motion. The recovery traces of ³⁹K, which predominantly undergoes quadrupole relaxation, can be represented by a linear combination of two exponential functions. The temperature dependences of the relaxation rates for ³⁹K can be described with a simple power law T₁⁻¹=αT². The spin-lattice relaxation rates for the ³⁹K nucleus in K₃H(SO₄)₂ and KHSO₄ crystals are in accordance with a Raman process dominated by a phonon mechanism.     

Electric monopole component in the 2+' → 2+ transition in 192Pt

Angular correlation measurements of K- and L-conversion electrons following the decay ¹⁹²Ir → ¹⁹²Pt have been made using a spectrometer with Ge(Li) and Si (Li) detectors. Absolute and relative internal conversion coefficients of transitions in ¹⁹²Pt were measured, using an ICC and prism β-spectrometers, to ≈ 2 % and values of δ_γ determined from the relative ICC. The experimental values measured in the study, A₂₂(K296γ316) = 0.138 ± 0.010, A₂₂(L296γ316) = 0.125 ± 0.013, α_K(296) = 0.0711 ± 0.0011, K/L_III = 9.65 ± 0.13. With δ_γ = + 5.4 ± 0.2, were employed for determining the E0/E2 amplitude ratios of conversion transitions, q(E0/E2), and the penetration parameter λ of the Ml component for the 2⁺' → 2⁺ (296 keV) transition in ¹⁹²Pt. The angular correlation measurements of L-conversion electrons enabled the elimination of one of two ranges of values of q and λ usually obtained. For the first time in our work, analysis of the e_Lγ angular correlation for the determination of the E0 component in the transition was carried out. As a result, q = +0.04 ± 0.05 with λ = ?4.5 ± 3.5 was obtained for the 296 keV transition. In this case, _ρ(E0) = 0.004 ± 0.005 agrees with _ρ(E0) = +0.006 determined theoretically by Kumar and Baranger for the 2⁺' → 2⁺ transition