New measurement of the electron magnetic moment using a one-electron quantum cyclotron

A new measurement resolves cyclotron and spin levels for a single-electron quantum cyclotron to obtain an electron magnetic moment, given by g/2=1.001 159 652 180 85 (76) [0.76 ppt]. The uncertainty is nearly 6 times lower than in the past, and g is shifted downward by 1.7 standard deviations. The new g, with a quantum electrodynamics (QED) calculation, determines the fine structure constant with a 0.7 ppb uncertainty--10 times smaller than for atom-recoil determinations. Remarkably, this 100 mK measurement probes for internal electron structure at 130 GeV.     

New determination of the fine structure constant from the electron value and QED

Quantum electrodynamics (QED) predicts a relationship between the dimensionless magnetic moment of the electron (g) and the fine structure constant (alpha). A new measurement of g using a one-electron quantum cyclotron, together with a QED calculation involving 891 eighth-order Feynman diagrams, determine alpha(-1)=137.035 999 710 (96) [0.70 ppb]. The uncertainties are 10 times smaller than those of nearest rival methods that include atom-recoil measurements. Comparisons of measured and calculated g test QED most stringently, and set a limit on internal electron structure.     

Ultraprecise atomic mass measurement of the alpha particle and 4He

The atomic masses of the alpha particle and 4He have been measured by means of a Penning trap mass spectrometer which utilizes a frequency-shift detector to observe single-ion cyclotron resonances in an extremely stable 6.0 T magnetic field. The present resolution of this instrument approaches 0.01 ppb [10 ppt (parts per trillion)] and is limited primarily by the effective stability (<5 ppt/h) of the magnet over hundreds of hours of observation. The leading systematic shift [at -202(9) ppt] is due to the image charge located in the trap electrodes. The new value for the atomic mass of the alpha particle is 4 001 506 179.147(64) nu and the corresponding value for the mass of 4He is 4 002 603 254.153(64) nu (nu=10(-9) u). The 16 ppt uncertainty is at least 20 times smaller than any previous determination.     

China rose petal as biotemplate to produce two-dimensional ceria nanosheets

China rose petal was used as robust biotemplate for the facile fabrication of novel ceria nanosheet with a thickness of about 7 nm via a continuous infiltration process. The presence of well-resolved peaks ([111], [200], [220], and [311]) for the products revealed the formation of the fluorite-structured CeO₂. The detailed characterization by field-emission scanning electron microscope (FESEM), field-emission transmission electron microscope (FETEM), and atomic force microscopy (AFM) exhibited the biomorphic structure of polycrystalline ceria film with the nanoparticle size of ca. 6.98 nm. Based on the surface chemistry and biochemistry processes, a possible mechanism for the formation of CeO₂ nanosheets is proposed. Furthermore, nitrogen adsorption–desorption measurement and photoluminescence spectrum (PL) were employed to characterize the samples. The ceria nanosheet showed the existence of mesopores (pores 2–4 nm diameter) on its surface and a broad emission ranging from 350 to 500 nm in photoluminescence spectrum. X-ray photoelectron spectroscopy analysis (XPS) confirmed that the mesoporous nanosheets possessed more surface vacancies than the bulk CeO₂; hence these hierarchical CeO₂ layers appear to be potential candidates for catalytic applications.     

谱线漂移对星载成像光谱仪辐射测量精度的影响

分析了谱线漂移在地面辐射定标、星上辐射定标和在轨对地观测等环节对成像光谱仪辐射测量的影响,建立了从实验室辐射定标到星上辐射定标再到在轨对地观测全过程的辐射传递模型,并通过仿真分析求解了成像光谱仪入瞳处辐射测量不确定与谱线漂移之间的关系。结果表明,谱线漂移导致的辐射测量误差与谱线漂移量和入瞳辐亮度的分布梯度成正比;光谱带宽偏差对测量精度的影响程度较中心波长误差高一个数量级。对于可见近红外(VNIR)波段平均光谱带宽10 nm、短波红外(SWIR)波段平均光谱带宽20 nm的典型成像光谱仪,要保证谱线漂移引起的辐射测量不确定度小于6%,实现成像光谱仪在轨观测时入瞳处的辐射测量绝对精度优于10%,可见近红外波段中心波长偏差应不大于2 nm,光谱带宽偏差应不大于0.1 nm,短波红外波段中心波长偏差应不大于3 nm,光谱带宽偏差应不大于0.1 nm。     

特洛伊木马方法及其应用最新进展

特洛伊木马方法是实验核天体物理中一种重要的间接测量方法,特别适合极低能区带电粒子裸核反应截面测量。在介绍特洛伊木马方法基本原理的基础上,重点讨论该方法近期在核天体物理应用中的一些重要实验结果,以及对未来研究的展望。主要介绍:AGB星s-过程关键中子源反应$ ^{{\rm{13}}}{\rm{C(\alpha ,n}}{{\rm{)}}^{{\rm{16}}}}{\rm{O}}$的间接测量,AGB星氟丰度超常现象相关核反应间接测量,以及最近热点–中等以上质量恒星碳燃烧核反应间接测量结果及相关争议。     

DFT/TDDFT study on the electronic structures and optoelectronic properties of a series of iridium(III) complexes based on quinoline derivatives in OLEDs

The electronic structures and photophysical properties of several heteroleptic iridium(III) complexes Ir(C^∧N)₂(acac) with acetylacetonate (acac) ligand, including 1 [C^∧N = 2‐phenylisoquinoline], 2 [C^∧N = 2‐biphenyl‐4‐yl‐quinoline], 3 [C^∧N = 2‐(fluoren‐2‐yl)‐quinoline], 4 [C^∧N = 2‐dibenzofuran‐3‐yl‐quinoline], 5 [C^∧N = 2‐dibenzothiophen‐3‐yl‐quinoline], and 6 [C^∧N = 2‐phenanthren‐2‐yl‐quinoline], have been investigated by density functional theory (DFT) and time‐dependent DFT. They show a wide color tuning of photoluminescence from orange–red (λ = 601 nm) to saturated red (λ = 685 nm). The calculated absorption and emission properties of complexes 1 and 2 are in good agreement with the available experimental data. Complex 6 has the smallest ionization potentials (IP) value, which is consistent with its highest occupied molecular orbital energy level, and thus its hole injection is easiest. Corresponding to its lowest unoccupied molecular orbital energy level, the assumed complex 5 has the large electron affinities value and enhanced electron injection ability compared to the others. These calculated results show that the assumed complex 3 may possess better charge transfer abilities than others and is the potential candidate for an efficient electrophosphorescent polymer‐based red‐emitting material. Copyright © 2013 John Wiley & Sons, Ltd.     

High precision measurement of the static dipole polarizability of cesium

The cesium 6(2)S(1/2) scalar dipole polarizability alpha(0) has been determined from the time-of-flight of laser cooled and launched cesium atoms traveling through an electric field. We find alpha(0)=6.611+/-0.009 x 10(-39) C m(2)/V=59.42+/-0.08 x 10(-24) cm(3)=401.0+/-0.6a(3)(0). The 0.14% uncertainty is a factor of 14 improvement over the previous measurement. Values for the 6(2)P(1/2) and 6(2)P(3/2) lifetimes and the 6(2)S(1/2) cesium-cesium dispersion coefficient C6 are determined from alpha(0) using the procedure of Derevianko and Porsev [Phys. Rev. A 65, 053403 (2002)]].     

New binding energy for the two-neutron halo of 11Li

The extended radius of a halo nuclide is very sensitive to the minute binding energy of its valence nucleons. The binding energy of 11Li has been measured with high precision by using the radio-frequency spectrometer MISTRAL at CERN's ISOLDE facility. The new two-neutron separation energy of 378+/-5 keV is 25% higher than the previously accepted value with an uncertainty 5 times smaller.     

First measurements with the neutron decay spectrometer a SPECT

The neutron decay spectrometera SPECT has been built to perform a precise measurement of the proton spectrum shape in the decay of free neutrons. Such a measurement allows a determination of the neutrino electron angular-correlation coefficienta . The present best experiments have an uncertainty of Δa/a = 5% and since the seventies there is no substantial improvement. Witha SPECT, we aim for an uncertainty which is lower by more than an order of magnitude, thus enabling us to perform several precise tests of the Standard Model. In our first beam time at the particle physics beam MEPHISTO at the Forschungsneutronenquelle Heinz Maier-Leibnitz, we studied the properties of the spectrometer. The most serious problem turned out to be the situation- and time-dependent behavior of the background. From the data sets from this beam time in which a background problem was not obvious, we could extract a value ofa = - 0.1151±0.0040^stat , but we could not quantify the background uncertainty. We show ways to deal with the background and other problems for future beam times.     

Direct mass measurement of the four-neutron halo nuclide 8He

A high-precision Penning trap mass measurement of the exotic 8He nuclide (T(1/2)=119 ms) has been carried out resulting in a reduction of the uncertainty of the halo binding energy by over an order of magnitude. The new mass, determined with a relative uncertainty of 9.2 x 10(-8) (deltam=690 eV) is 13 keV less bound than the previously accepted value. The mass measurement is of great relevance for the recent charge-radius measurement of 8He [P. Mueller, Phys. Rev. Lett. 99, 252501 (2007).10.1103/PhysRevLett.99.252501]. The 8He mass is the first result from the newly-commissioned Penning trap: TITAN (TRIUMF's Ion Trap for Atomic and Nuclear science) at the ISAC (Isotope Separator and Accelerator) radioactive beam facility at TRIUMF.     

Measurements of the strong-interaction widths of the kaonic (3)He and (4)He 2p levels

The kaonic (3)He and (4)He X-rays emitted in the [Formula: see text] transitions were measured in the SIDDHARTA experiment. The widths of the kaonic (3)He and (4)He 2p states were determined to be [Formula: see text], and [Formula: see text], respectively. Both results are consistent with the theoretical predictions. The width of kaonic (4)He is much smaller than the value of [Formula: see text] determined by the experiments performed in the 70's and 80's, while the width of kaonic (3)He was determined for the first time.     

K-K electron capture from adenine and CO2 molecule by fast carbon ions using KLL-Auger electron technique

The experimental measurement of total electron transfer cross section in Bragg peak energy region is important to understand energy loss in the biomolecular system. In this study, we have measured state selective, K-K electron capture and K-ionization cross sections for adenine (C ₅H ₅N ₅) in collisions with fast (2.5–5 MeV/u) C ions. These are compared with the data for smaller gas molecule, CO ₂. These are derived from a study of the KLL-Auger electron emission yields as a function projectile charge state. The K-ionization cross-section (σ_KI) data are compared with the ECUSAR (united and separated atom [USA] approximation with energy loss [E], Coulomb deflection [C], and relativistic [R] corrections) model calculation. The measured σ_KI data and the calculations are in good agreement. The K-K transfer cross-section (σ_K−K) data are compared with the CPSSR (perturbed stationary state [PSS] with Coulomb deflection [C] and relativistic corrections [R]) calculation that underestimates the measured data for such symmetric collision system. The energy dependence of σ_K−K for adenine is found to be flat in contrast to a sharp variation predicted by the model. The K-transfer cross section is found to be substantial fraction of the K-ionization.     

New determination of the fine structure constant and test of the quantum electrodynamics

We report a new measurement of the ratio h/m(Rb) between the Planck constant and the mass of (87)Rb atom. A new value of the fine structure constant is deduced, α(-1)=137.035999037(91) with a relative uncertainty of 6.6×10(-10). Using this determination, we obtain a theoretical value of the electron anomaly a(e)=0.00115965218113(84), which is in agreement with the experimental measurement of Gabrielse [a(e)=0.00115965218073(28)]. The comparison of these values provides the most stringent test of the QED. Moreover, the precision is large enough to verify for the first time the muonic and hadronic contributions to this anomaly.     

A New Form of the Crystal Potential in BCC Iron

By approximating the electron density in the crystal as a sum of spherically symmetrical atomic densities using the Green's function, a new exact relation for the Coulomb potential is derived. The relation allows calculation of its values at any point of a unit cell. An attractive potential of the Coulomb hole that screens the electron long-range action is obtained. The method is applied in practice to the bcc iron for the [100], [110], and [111] directions.     

Uncertainty and routine use of Aerial l-alanine – Electron spin resonance dosimetry system

Aerial l-alanine pellet dosimeter is characterized by MiniScope MS300 electron spin resonance spectrometer measurements using Aer'EDE Version 2.0.4. software for dose calculation. The measurement traceability is achieved by Aerial dosimetry laboratory where dosimeters for calibration curve were irradiated by electron beam accelerator. Dose determinations in Aerial are traceable to National Physical Laboratory (NPL). The software used for construction of calibration curve gives also the standard deviation of the residuals of measurements for calibration that is used for dose uncertainty calculation. In aim to determine whether this value can actually be taken as absorbed dose uncertainty during usage of this dosimetry system, alanine dosimeters were irradiated with doses between 5 and 32 kGy by ⁶⁰Co laboratory source for internal calibration. The dose rate at the places for irradiation was (20 ± 0.5) mGy s⁻¹ determined by Fricke dosimeter. Measurement of each irradiated dosimeter was repeated ten times in ten days. The results of measurements were analyzed to identify the sources of uncertainty, as well as their quantification in evaluation of total measurement uncertainty. In addition to statistical effects, the very low dose rate that was used for the irradiation of alanine dosimeters affects the measurements of absorbed dose, particularly for higher absorbed doses where the measured dose can be up to 3% lower than the real.     

Influence of the colored noise on determining the period of a torsion pendulum

Based on statistical properties, two typical models are considered to calculate the uncertainties for some random noise sequences on the period extraction of a torsion pendulum, which is important and instructive in the measurement of gravitational constant G with the time-of-swing method. An expression of the uncertainty for the period measurement is obtained, which is dependent on the ratio ?t/(1/λ) where ?t is the interval of the sample time and 1/λ is the length of the correlation time. The result of processing experimental data shows that as the interval of the sample time ?t gradually shortens, the uncertainty of the period becomes smaller, and further when the ratio ?t/(1/λ) is less than 1, the uncertainty remains substantially unchanged.     

The excitation energies,ionization potentials and oscillator strengths of neutral and ionized species of Uub (Z = 112) and the homologue elements Zn,Cd and Hg

Multi-configuration Dirac-Fock method (MCDF) is employed to calculate excitation energies, ionization potentials and oscillator strengths for all neutral and up to 5 times ionized species of element Uub, as well as the homologue elements Zn, Cd and Hg. On the basis of not too extended MCDF calculations, we studied some peculiar properties of element Uub resulting from its stronger relativistic and electron correlation effects. Using an extrapolative scheme, improved ionization potentials of Uub were obtained with an uncertainty of less than 0.5 eV. Furthermore, we calculated the low-lying resonance excitation energies, absorption oscillator strengths and the first ionization potential for Hg and Uub using large scale MCDF calculations, which improved the uncertainty of the excitation energies to less than 0.25 eV for element Hg. We hope that such calculations yield good results for element Uub.     

Calculation of the one- and two-loop lamb shift for arbitrary excited hydrogenic states

General expressions for quantum electrodynamic corrections to the one-loop self-energy [of order alpha(Zalpha)6] and for the two-loop Lamb shift [of order alpha2(Zalpha)6] are derived. The latter includes all diagrams with closed fermion loops. The general results are valid for arbitrary excited non-S hydrogenic states and for the normalized Lamb shift difference of states, defined as Delta N = n3deltaE(nS) - delta E(1S). We present numerical results for one-loop and two-loop corrections for excited S, P, and D states. In particular, the normalized Lamb shift difference of states is calculated with an uncertainty of order 0.1 kHz.     

Point defects and diffusion in NiO

A defect model for NiO is developed and is fit to the electrical-conductivity data [26], the deviation-from-stoichiometry data [7], and the cation-self-diffusion data [14, 17]. This model involves neutral, singly charged, and doubly charged nickel vacancies and charge-compensating electron holes. Both singly and doubly charged cation vacancies are required to explain the data; neutral cation vacancies (if present) are not required by the present data. However, the jump frequencies of the two types of charged cation vacancies are generally not equal; the doubly charged cation vacancy moves with the smaller activation enthalpy. The defect data are quantitatively consistent with the chemical-diffusion data [26] and with a correlation factor?v = 0.75.