机磷农药的 31P NMR 谱的研究

采用600 MHz NMR谱仪较详细地研究了不同类型有机磷农药的NMR谱图, 分析了复杂偶合、直变异构、受阻旋转、手性碳原子等因素对有机磷农药的NMR谱图影响.     

THE 31P NMR INVESTIGATION OF PHOSPHORUS BURNS

为了明确磷烧伤创面及吸收毒性物质的化学形式及分布.作者采用\+\{31\}P NMR波谱,研究皮下注射黄磷、磷酸及磷烧伤后创面残留、肝脏及脑组织吸收的元素磷及其化合物含量.其结果皮下注射非致死与致死剂量的黄磷后,肝脏可测到元素磷的吸收,磷燃烧后创面磷绝大部分转化为磷酸及其结合物,极少部分以元素磷形式存在.致死面积的磷酸烫伤与磷烧伤后肝脏区域磷酸增加4～5倍,未检测到元素磷的波谱,各组脑组织均未检测到元素磷峰,而磷酸峰只有微小的增加.结论为磷烧烧后吸收的主要中毒物质与创面残留的主要化学物质一致,磷烧伤中毒的致死性主要是创面磷酸吸收所致.     

Electronic properties of HfXY intermetallic compounds (X = Si, Ge; Y = S, Se, Te)

Muonium, with a positive muon as the nucleus is considered a light isotope of hydrogen displaying a close chemical analogy to this atom. It offers a unique opportunity to study the behaviour of hydrogen in diamond at very low concentrations. The mass difference, however, implies that dynamical effects will be distinct. The bond centred muonium (Mu _BC ) state in diamond is easily observed and there is a very good correlation between theoretical and experimental hyperfine parameters (Schneider et al., Phys. Rev. Lett. 71(4):557–560, 1993). Curiously, despite its predicted stability, the bond centred hydrogen state has not yet been observed in diamond. Following the discovery of hydrogen dopant states in certain wide band gap metal oxides, and the possibility of hydrogen related molecular dopants in diamond, the study of hydrogen in diamond is important. Although it is evident from its hyperfine parameters that Mu _BC is not a shallow donor, the question still arises as to where the Mu _BC state in diamond might lie in the band gap. Accordingly, measurements of the high temperature stability of Mu _BC have been performed in a search for its possible ionization. The results are consistent with such an ionization, as the disappearance of Mu _BC polarisation (setting in near 1000 K) is correlated with the slight increase in the population of the diamagnetic μ⁺ species.     

The α-transfer reactions 27Al(6Li,d)31P, 29Si(6Li,d)33S and 31P(6Li,d)35Cl at 36 MeV

The α-transfer reactions ²⁷Al(⁶Li, d)³¹P, ²⁹Si(⁶Li, d)³³S and ³¹P(⁶Li, d)³⁵Cl have been studied at a ⁶Li energy of 36 MeV. Absolute cross sections and angular distributions have been measured and an exact finite-range distorted-wave Born approximation analysis assuming a direct cluster transfer has been used to extract from the data α-particle spectroscopic strengths for levels populated in ³¹P, ³³S and ³⁵Cl in the three reactions respectively. The results show that in the case of most of the low-lying excited states of ³¹P, a single value of L of the transferred α-particle contributes, though a multiplicity of L-values are allowed by angular momentum selection rules. It is also found that the α-particle spectroscopic strength of the ground state of ³¹P is a factor of 2 more than the strengths of the ground states of ³³S and ³⁵Cl. The α-spectroscopic strengths of ground states of these, as well as other odd-A s-d shell nuclei, are compared with the presently available shell model calculations.     

Pressure-induced phase transitions in the ZrXY (X= Si,Ge, Sn;Y= S,Se, Te) family compounds

Pressure is an effective and clean way to modify the electronic structures of materials, cause structural phase transitions and even induce the emergence of superconductivity. Here, we predicted several new phases of the ZrXY family at high pressures using the crystal structures search method together with first-principle calculations. In particular, the ZrGeS compound undergoes an isosymmetric phase transition from P4/nmm-I to P4/nmm-II at approximately 82 GPa. Electronic band structures show that all the high-pressure phases are metallic. Among these new structures, P4/nmm-II ZrGeS and P4/mmm ZrGeSe can be quenched to ambient pressure with superconducting critical temperatures of approximately 8.1 K and 8.0 K, respectively. Our study provides a way to tune the structure, electronic properties, and superconducting behavior of topological materials through pressure.     

31P and 11B NMR in amorphous NiPB alloys near the paramagnetic-ferromagnetic transition

Knight-shift and nuclear spin-lattice relaxation time measurements have been performed between 4.2°K and room temperature on ¹¹B and ³¹P in amorphous NiPB alloys near the para-ferromagnetic transition. The EFG parameters on ¹¹B were found to be ν_Q=200(±20)kHz and η = 0.35 (±0.10). Knight-shift and Korringa spin-lattice relaxation are mainly due to mechanisms involving p electrons. The effect of Ni magnetic clouds results in a broadening of the linewidth. We observed also the occurence of a Giovannini-Heeger-like contribution to the spin-lattice relaxation rate.     

The 20Ne(12C,p)31P, 20Ne(12C,d)30P and 20Ne(12C, α)28Si reactions in the region of the coulomb barrier

The excitation functions of the ²⁰Ne(¹²C, p)³¹P, ²⁰Ne(¹²C, d)³⁰P. and ²⁰Ne(¹²C, α)²⁸ Si reactions were measured at bombarding energies between 6.9 and 16.9 MeV (c.m.) by steps of 156 keV, at an average lab angle of 2.82°. The average coherence width of states in the compound nucleus, ³²S, populated in the reactions was deduced through the analysis of the fluctuations in the measured excitation functions. The result agrees with the average compound nucleus width predicted by the Hauser-Feshbach expression. The fluctuation analysis shows that these reactions proceed mainly through the formation of a compound nucleus. A cross correlation analysis revealed that the fluctuations in the different excitation functions are statistically independent and that there is no evidence of intermediate structure resonances.     

Electronic properties of chalcopyrite CuAlX2(X=S,Se,Te) compounds

We present results of the band structure and density of states for the chalcopyrite compounds CuAlX₂ (X=S,Se,Te) using the state-of-the-art full potential linear augmented plane wave (FP-LAPW) method. Our calculations show that these compounds are direct band gap semiconductors. The energy gap decreases when S is replaced by Se and Se replaced by Te in agreement with the experimental data. The values of our calculated energy gaps are closer to the experimental data than the previous calculations. The electronic structure of the upper valence band is dominated by the Cu-d and X-p interactions. The existence of Cu-d states in the upper valence band has significant effect on the optical band gap.     

Phase stability and temperature effect in ScX (X=S,Se and Te) compounds

Based on first-principles calculations, the structural stability and temperature effect in ScX (X=S, Se and Te) compounds are studied with three typical structures of B1 (NaCl-type), hcp (NiAs-type) and β-hcp (inverse Li₂O₂-type). Their dynamic stability has been verified using phonon mode analysis and molecular dynamics simulations. From the total energy calculations, we find that the most stable ground state structures are B1 for ScS, and hcp for ScSe and ScTe, respectively. Moreover, structural stabilities at finite temperature are studied with the combination of phonon dependent dynamics analysis and first-principles calculations, which reveals a phase transition from hcp to B1 in ScSe around 230 K and a phase transition from hcp to β-hcp in ScTe around 460 K, in accordance with experimental findings. The energy barrier and pathway along the phase transformation from hcp to β-hcp ScTe are also calculated and analyzed by the solid-state nudged elastic band method.     

Spin and parity assignments for 35Cl levels from the 31P(α, p)34S reaction

³⁵Cl states at excitation energies between 9.9 and 11.8 MeV have been identified through sharp resonances in the ³¹P(α, p_o)³⁴S excitation functions at 25°, 105° and 155° for E_α = 3.25–5.50 MeV. Forty-eight on-resonance angular distributions, normalized to an absolute cross section scale, have been subjected to single-level and two-level analyses resulting in spin and parity assignments for each resonance. Approximately half the resonances were of the pure single-state type, having unique angular distribution shapes. Data from 12 resonances of an earlier experiment ¹) were analyzed with the same theory, extending the diagnostics down to a ³⁵Cl excitation energy of 9.1 MeV. A set of optical potentials consistent in all four reactions that this experimental program encompasses has been incorporated in the present analysis. Validity of the optical potential is demonstrated for α-particles elastically scattered by ³¹P.     

核磁共振磷谱在混合取代聚磷腈合成中的应用研究

用核磁共振磷谱对具有4-丙氧羰苯氧基和甘氨酸乙酯侧链的混合取代聚磷腈的合成过程进行监测. 实验结果表明,聚二氯磷腈与4-丙氧羰苯氧基钠的反应及其中间产物与甘氨酸乙酯的反应分别需要20 h 和24 h才能完成. 生成的最终产物中,既含有混合取代型链节,也含有单取代型链节,但从整个分子来看,两种取代基的相对含量之比为0.49∶0.51. 这些结果对于深入了解此类高分子反应的机理,进一步优化混合取代聚磷腈的合成条件,提高合成收率提供了依据.      

Investigation of states in 30P via the 30Si(3He,t)30P reaction at 30 MeV

The ³⁰Si(³⁰He, t)³⁰P reaction has been measured for about 100 levels in ³⁰P with E_x < 8.8 MeV. Little selectivity in the population of states has been observed. For 75 levels angular distributions have been analysed using a “fingerprint method” by determining the L-value from a comparison in shape with transitions to states with known J^π. For possible mixed L-transitions a dominance of the higher L-value is observed for almost all cases. Coulomb displacement energy calculations utilizing shell-model wave functions have been used to identify T = 1 states.     

Elastic magnetic electron scattering from 29Si and 31P

Elastic magnetic electron-scattering form factors from ²⁹Si and ³¹P have been measured in the range of momentum transfer from 1.0 to 2.8 fm^?1. Analysis of the data using a particle-core-coupling model yields $\text{2}\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ occupation probabilities for the valence nucleon of 0.46 ± 0.01 for the neutron in ²⁹Si and 0.48 ± 0.01 for the proton in ³¹P. The radius of the $\text{2}\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ proton orbit in ³¹P has been found to be (5.3^+2.6_?1.5)% larger than the corresponding neutron orbit in ²⁹Si. Recent large-basis shell-model calculations of the form factors do not accurately reproduce the experimental results.     

Electronic and mechanical properties of half-metallic half-Heusler compounds CoCrZ(Z=S,Se, and Te)

The electronic structures, magnetic properties, half-metallicity, and mechanical properties of half-Heulser compounds CoCrZ(Z = S, Se, and Te) were investigated using first-principles calculations within generalized gradient approximation based on the density function theory. The half-Heusler compounds show half-metallic properties with a half-metallic gap of 0.15 eV for CoCrS, 0.10 eV for CoCrSe, and 0.31 eV for CoCrTe at equilibrium lattice constant, respectively. The total magnetic moments are 3.00μB per formula unit, which agrees well with the Slater-Pauling rule. The half-metallicity,elastic constants, bulk modulus, shear modulus, Pough's ratio, Frantesvich ratio, Young's modulus, Poisson's ratio, and Debye temperature at equilibrium lattice constant and versus lattice constants are reported for the first time. The results indicate that the half-Heulser compounds CoCrZ(Z = S, Se, and Te) maintain the perfect half-metallic and mechanical stability within the lattice constants range of 5.18-5.43  for CoCrS, 5.09-5.61  for CoCrSe, and 5.17-6.42  for CoCrTe,respectively.     

Frequency shifts in pulsed NMR for 3He(A)

The ringing frequency recently observed by Osheroff and Corruccini in pulsed NMR experiments on the A-phase of ³He is calculated from Leggett's resonance equations. For large magnetic fields the frequency is $\text{Ω = γ}\text{H}\text{+ (Ω}{}^2{}_{\mathrm{<mtext>L</mtext>}}\text{/8γH)(1 + 3}\text{cos}\text{θ)}$, where θ is the tipping angle, and Ω_L is the longitudinal resonance frequency     

Spectroscopy of 32P (II)

Spins, parities and transition probabilities of levels in ³²P at E_x > 3.5 MeV have been determined with the ²⁹Si(α, pγ)³²P reaction at bombarding energies of E_α = 12.80, 12.93 and 16.30 MeV. Proton-gamma angular correlation experiments and DSA lifetime measurements lead to six unambiguous spin assignments and to many spin limitations. The measured mixing and branching ratios yield many transition strengths for dipole and electric quadrupole transitions. Five, sofar unknown, energy levels are reported. A doublet at 4.03 MeV excitation energy and a high-spin state (E_x = 4.27 MeV; J^π = 5^?) were observed. Shell-model predictions have been compared to the present experimental results.     

Physical properties of several M2Mo6X6 compounds (M = GROUP IA METAL; X = Se,Te)

We report the physical properties of the pseudo one dimensional ternary molybdenum chalcogenides M₂Mo₆X₆ (M = K, Rb,Cs,Tl;X = Se, Te) measured on single crystals grown at high temperature. For Group IA metals (Rb,..,Cs) the transport properties evolve from a metallic to a semiconducting-like behavior on decreasing the temperature. Over the same temperature range the Group IIIA compound (Tl₂Mo₆Se₆) remains metallic and even superconducts at 5.1K. The susceptibility of these materials is weakly diamagnetic and does not reveal anomalied correlated to the onset of the broad metal-nonmetal transition, except perhaps for Cs₂Mo₆Te₆. A variation of the electronic interchain coupling is proposed to explain the difference between the Group IA and IIIA metal compounds. In the absence of evidence of three dimensional ordering at low temperature, we suggest that the broad metal-nonmetal transition is due to a fluctuating Pierls gap that is uncorrelated from one Mo chain to the next.     

Lifetimes of the levels 31P, 41P and 51P in Li II by the beam-foil technique

Radiative lifetimes of the Li II levels 3¹P, 4¹P and 5¹P are extracted from the observed vacuum-UV-transitions 3¹P → 2¹S, 4¹P → 2¹S, and 5¹P → 2¹S, respectively. The measured values agree well with theory.     

Microscopic and macroscopic DWBA analysis of the reactions 28Si(α, d)30P, 32S(d, α)30P and 32S(α, d)34Cl studied at Eα = 50MeV and Ed = 40MeV

The reactions ²⁸Si(α, d)³⁰P, ³²S(d, α)³⁰P and ³²S(α, d)³⁴Cl have been studied at E_α = 50 MeVand E_d = 40 MeV. The angular distributions have been analysed in terms of the single-step, zero-range DWBA with microscopic as well as macroscopic form factors. By requiring an almost identical shape in the microscopic and macroscopic radial form factors for all L-values with L ? 6 the size parameters of the Woods-Saxon well in which the transferred cluster is bound to the nucleus were determined as r₀ = 1.15 fmanda = 0.76 fm. Despite the differences between the two approaches with these parameters the shape of the microscopic angular distribution is well reproduced and the corresponding strengths agree to within 25%. The method has been applied to the three reactions and relative two-nucleon spectroscopic factors have been deduced. A comparison is made with the results of two shell-model calculations.