Research on Measurement of 182Hf with HI-13 AMS System

¹⁸²Hf with half-life of about (8.90±0.09) Ma is an extinct radionuclide and can only be produced by a supernova explosion in nature. Therefore ¹⁸²Hf is an ideal candidate nuclide for the study on possible supernova explosions in the vicinity of the earth within the last 100 million years. In addition, ¹⁸²Hf is a long-lived radionuclide of particular interest for nuclear engineering. Accurate measurement of ultra-trace ¹⁸²Hf is very important for reactor design,studies on nuclear cosmo-physics and other fields. With an accelerator mass spectrometry (AMS), it is possible to detect the trace amounts of ¹⁸²Hf. In this paper, the detection method of ¹⁸²Hf with HI-13 AMS system at China Institute of Atomic Energy (CIAE) and the chemical procedures to reduce ¹⁸²W interference are presented. The energy and TOF two-dimension spectra of ¹⁸²Hf and ¹⁸³W for blank and a series of standard samples have been obtained, respectively. The ¹⁸²W contribution to the counts in ¹⁸²Hf peak was corrected by ¹⁸³W normalization. The detection sensitivity of this AMS facility for ¹⁸²Hf/¹⁸⁰Hf ratio measurement is about 4.15±10^－11 at present.     

加速器质谱测量182Hf的效率研究

182Hf是长寿命放射性核素,其半衰期约为9×106 a. 测量环境样品中的182Hf对核天体物理学和核工程的研究具有重要的意义. 加速器质谱(AMS)作为一门超高灵敏核分析技术,可以测量样品中极其微量的182 Hf. 本工作在中国原子能科学研究院HI 13串列加速器核物理国家实验室的AMS装置上对182 Hf的AMS效率进行了测量,得到了初步的测量结果.     

Limit on the present temporal variation of the fine structure constant

The comparison of different atomic transition frequencies over time can be used to determine the present value of the temporal derivative of the fine structure constant alpha in a model-independent way without assumptions on constancy or variability of other parameters, allowing tests of the consequences of unification theories. We have measured an optical transition frequency at 688 THz in 171Yb+ with a cesium atomic clock at 2 times separated by 2.8 yr and find a value for the fractional variation of the frequency ratio f(Yb)/f(Cs) of (-1.2+/-4.4)x10(-15) yr(-1), consistent with zero. Combined with recently published values for the constancy of other transition frequencies this measurement sets an upper limit on the present variability of alpha at the level of 2.0x10(-15) yr(-1) (1sigma), corresponding so far to the most stringent limit from laboratory experiments.     

Limits on variations in fundamental constants from 21-cm and ultraviolet Quasar absorption lines

Quasar absorption spectra at 21-cm and UV rest wavelengths are used to estimate the time variation of x [triple-bond] alpha(2)g(p)mu, where alpha is the fine structure constant, g(p) the proton g factor, and m(e)/m(p) [triple-bond] mu the electron/proton mass ratio. Over a redshift range 0.24 < or = zeta(abs) < or = 2.04, (Deltax/x)(weighted)(total) = (1.17 +/- 1.01) x 10(-5). A linear fit gives x/x = (-1.43 +/- 1.27) x 10(-15) yr(-1). Two previous results on varying alpha yield the strong limits Deltamu/mu = (2.31 +/- 1.03) x 10(-5) and Deltamu/mu=(1.29 +/- 1.01) x10(-5). Our sample, 8 x larger than any previous, provides the first direct estimate of the intrinsic 21-cm and UV velocity differences 6 km s(-1).     

Study of the gamma emission from the 31-yr isomer of 178Hf induced by x-ray irradiation

A sample containing 6.3×10¹⁴ nuclei of the 16⁺ isomer of ¹⁷⁸Hf having a half-life of 31 yr and an excitation energy of 2.446 MeV was irradiated with x-ray pulses from a device operated at 15 mA to produce bremsstrahlung with an endpoint energy of 90 keV. The gamma spectra of the isomeric target were taken with a Ge detector. The intensity of the 325.5-keV (6⁺ → 4⁺) transition in the ground-state band of ¹⁷⁸Hf was found to increase by about 2%. Such an enhanced decay of the ¹⁷⁸Hf isomer is consistent with an integrated cross section value of 3×10^?23 cm² keV if resonance absorption occurs within energy ranges corresponding to the maxima of the x-ray flux, either near 20 keV or at the energies of the characteristic emission lines of W.     

Complete two loop bosonic contributions to the muon lifetime in the standard model

The last missing correction to the muon lifetime in the standard model at O(alpha(2)) coming from gauge and Higgs boson loops is presented. The associated contribution to the parameter Deltar in the on-shell scheme ranges from 6x10(-5) to -4x10(-5) for Higgs boson masses from 100 GeV to 1 TeV. This result translates into a shift of the W boson mass which does not exceed +/-1 MeV in the same range and amounts, in particular, to approximately -0.8 MeV for a 115 GeV Higgs boson.     

852.3 nm激光线共振激发Cs蒸气的荧光光谱

研究了Cs蒸气被单模半导体激光器的852.3 nm线激发产生的荧光光谱。由Cs,Cs₂的荧光及其强度确定了在受激Cs-Cs₂系统中的若干碰撞和辐射过程。高位态原子线是由Cs(6P_3/2)+ Cs(6P_3/2)到Cs(6D,8S)的碰撞能量合并形成的,Cs₂(B 1∏_u)带则由Cs(6P)+Cs₂(X 1Σ+_g)碰撞转移产生。通过激发转移、能量碰撞合并和Cs₂-Cs碰撞传能研究了6 2P原子的精细结构混合,得到了6P_3/2→6P_1/2碰撞转移速率系数是(5.2±2.1)×10-11 cm3·s-1,给出了过程Cs₂(B 1∏_u)+Cs(6S)→Cs₂(X 1Σ+_g)+Cs(6P_1/2)的速率系数是(1.0±0.4)×10-9 cm3·s-1。     

New limits on the drift of fundamental constants from laboratory measurements

We have remeasured the absolute 1S-2S transition frequency nu(H) in atomic hydrogen. A comparison with the result of the previous measurement performed in 1999 sets a limit of (-29+/-57) Hz for the drift of nu(H) with respect to the ground state hyperfine splitting nu(Cs) in 133Cs. Combining this result with the recently published optical transition frequency in 199Hg+ against nu(Cs) and a microwave 87Rb and 133Cs clock comparison, we deduce separate limits on alpha/alpha=(-0.9+/-2.9) x 10(-15) yr(-1) and the fractional time variation of the ratio of Rb and Cs nuclear magnetic moments mu(Rb)/mu(Cs) equal to (-0.5+/-1.7) x 10(-15) yr(-1). The latter provides information on the temporal behavior of the constant of strong interaction.     

Theg-factor of the 2+ state of180W and quadrupole moment ratios observed for180W and180Hf by the Mössbauer technique

By Mössbauer absorption experiments the magnetic hyperfine splitting has been observed for the 2+ states of¹⁸⁰W and¹⁸²W in a tungsten iron alloy (3.6 at%W). Since theg-factor of the 2+ state of¹⁸²W is known the measured splitting of the¹⁸²W line could be used for the calibration of the magnetic hyperfine field and the measurement with¹⁸⁰W gave then for the unknowng ₂₊-factor of¹⁸⁰W: $$g_{2 + } (^{180} W) = 0.260 \pm 0.017.$$ By use of a WO₃ absorber the electric quadrupole splittings in the same states were measured. The ratio of the quadrupole moments was derived $$\frac{{Q_{2 + } (^{180} W)}}{{Q_{2 + } (^{182} W)}} = 0.983 \pm 0.022.$$ This ratio is somewhat smaller, but more accurate than the weighted means of previous results and in disagreement with the theoretical prediction. A similar measurement with¹⁷⁸Hf and¹⁸⁰Hf and a HfO₂ absorber gave $$\frac{{Q_{2 + } (^{178} Hf)}}{{Q_{2 + } (^{180} Hf)}} = 1.052 \pm 0.021.$$ This result is larger than the average of previous measurements and agrees with theory. The isomer shifts of the Mössbauer lines of¹⁸⁰W and¹⁸²W were measured for sources in a tantalum metal environment and for absorbers of metallic tungsten. Different signs were observed which indicate that the mean squared charge radius of the 2+ state of¹⁸²W is larger than that of the ground state whereas for¹⁸⁰W the ground state has the larger 〈r ²〉-value.     

Stability of the proton-to-electron mass ratio

We report a limit on the fractional temporal variation of the proton-to-electron mass ratio as 1/(m(P)/m(e)) partial differential/partial differential(t)(m(P)/m(e))=(-3.8+/-5.6) x 10(-14) yr(-1), obtained by comparing the frequency of a rovibrational transition in SF6 with the fundamental hyperfine transition in Cs. The SF6 transition was accessed using a CO2 laser to interrogate spatial 2-photon Ramsey fringes. The atomic transition was accessed using a primary standard controlled with a Cs fountain. This result is direct and model-free.     

The evaluation of half-lives and other decay data used in nuclear astrophysics and cosmochronology

The current status of some decay data used in nuclear astrophysics and cosmochronology is presented. The half-life of ⁷⁹Se has been evaluated as 3.6(3) × 10⁵ yr. The total energy of non-neutrino radiation released in act of ³⁷Ar decay has been obtained being 2.709 (16) keV per disintegration. The recommended half-life values of the long-lived radionuclides (T _1/2 ≳ 10⁶ yr) of ²⁶Al, ⁴⁰K, ⁵³Mn, ⁶⁰Fe, ⁸⁷Rb, ⁹³Zr, ⁹⁸Tc, ¹⁰⁷Pd, ¹²⁹I, ¹³⁵Cs, ¹⁴⁶Sm, ¹⁷⁶Lu, ¹⁸²Hf, ¹⁸⁷Re, ²⁰⁵Pb, ²³²Th, ²³⁵U, ²³⁸U, ²⁴⁴Pu, and ²⁴⁷Cm are given based on the evaluations published until 2010.     

Precision measurement of neutrino oscillation parameters with KamLAND

The KamLAND experiment has determined a precise value for the neutrino oscillation parameter Deltam21(2) and stringent constraints on theta12. The exposure to nuclear reactor antineutrinos is increased almost fourfold over previous results to 2.44 x 10(32) proton yr due to longer livetime and an enlarged fiducial volume. An undistorted reactor nu[over]e energy spectrum is now rejected at >5sigma. Analysis of the reactor spectrum above the inverse beta decay energy threshold, and including geoneutrinos, gives a best fit at Deltam21(2)=7.58(-0.13)(+0.14)(stat) -0.15+0.15(syst) x 10(-5) eV2 and tan2theta12=0.56(-0.07)+0.10(stat) -0.06+0.10(syst). Local Deltachi2 minima at higher and lower Deltam21(2) are disfavored at >4sigma. Combining with solar neutrino data, we obtain Deltam21(2)=7.59(-0.21)+0.21 x 10(-5) eV2 and tan2theta12=0.47(-0.05)+0.06.     

Coulomb excitation paths of high-K isomer bands in 178Hf

Three distinctly different mechanisms are shown to populate the K(pi)=6(+) (t(1/2)=77 ns), 16(+) (31 yr), and 8(-) (4 s) isomer bands of 178Hf by Coulomb excitation. High spin states of the three isomer bands were populated by Coulomb excitation of a hafnium target with a 650 MeV 136Xe beam. Although direct population of high-K bands is highly K-forbidden, isomer bands in 178Hf were populated up to spins 13(+)(K=6), 20(+)(K=16), and 14(-)(K=8) with in-band gamma yields of approximately 10(-4) of the ground state band. The data are consistent with a rapid increase in K mixing with increasing spin in the isomer bands.     

光谱法研究2-(4-二甲氨基苯基)-5-氟-6-吗啉-1-氢-苯并咪唑与小牛胸腺DNA的相互作用

研究了2-(4-二甲氨基苯基)-5-氟-6-吗啉-1-氢-苯并咪唑(1)在不同pH条件下的紫外-可见吸收光谱,采用非线性最小二乘法得出分子1的三级加质子常数lgβ₁, lgβ₂, lgβ₃分别为4.96±0.03, 5.72±0.07和7.95±0.10。当pH 3.40时,分子1主要以一价离子状态存在,紫外-可见吸收光谱及荧光光谱表明该条件下分子与小牛胸腺DNA存在明显的相互作用,并得出分子1与DNA的结合常数K_b为(2.30±0.10)×104 mol-1·L。当分子浓度为10-8～1.2×10-6 mol·L-1时,荧光强度随DNA含量的增加而线性增强,分子1是一种潜在的测定DNA的定量试剂。     

Constraints on changes in fundamental constants from a cosmologically distant OH absorber or emitter

We have detected the four 18 cm OH lines from the z approximaetely 0.765 gravitational lens toward PMN J0134-0931. The 1612 and 1720 MHz lines are in conjugate absorption and emission, providing a laboratory to test the evolution of fundamental constants over a large lookback time. We compare the HI and OH main line absorption redshifts of the different components in the z approximately 0.765 absorber and the z approximately 0.685 lens toward B0218 + 357 to place stringent constraints on changes in F triple-bond g(p)[alpha(2)/mu](1.57). We obtain [DeltaF/F] = (0.44 +/- 0.36(stat) +/- 1.0(sys)t) x 10(-5), consistent with no evolution over the redshift range 0 < z < or = 0.7. The measurements have a 2sigma sensitivity of [Deltaalpha/alpha] < 6.7 x 10(-6) or [Deltamu/mu] < 1.4 x 10(-5) to fractional changes in alpha and mu over a period of approximately 6.5 G yr, half the age of the Universe. These are among the most sensitive constraints on changes in mu.     

Measurement of the K(L) charge asymmetry

We present a measurement of the charge asymmetry delta(L) in the mode K(L)-->pi(+/-)e(-/+)nu based on 298 x 10(6) analyzed decays. We measure a value of delta(L) = [3322+/-58(stat)+/-47(syst)]x10(-6), in good agreement with previous measurements and 2.4 times more precise than the current best published result. The result is used to place more stringent limits on CPT and DeltaS = DeltaQ violation in the neutral kaon system.     

Is a Griffiths phase a prerequisite for colossal magnetoresistance?

Detailed measurements of the magnetic and transport behavior of the two La(1-x)Ca(x)MnO(3) single crystals exhibiting colossal magnetoresistance are summarized. The x=0.21 sample exhibits unusual exponents (delta = 20+/-1, gamma = 1.71+/-0.1, beta = 0.09+/-0.01, T(C) = 182+/-1 K) and, more importantly, a Griffiths phase characterized by an exponent lambda = 0.70+/-0.2. By contrast, the x=0.20 specimen displays Heisenberg model behavior with no evidence of such a phase. Thus while a Griffiths phase accounts for the behavior of La(1-x)Ca(x)MnO(3) near optimal doping, it does not appear to be a prerequisite for colossal magnetoresistance in this system.     

Limit on the temporal variation of the fine-structure constant using atomic dysprosium

Over 8 months, we monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These frequencies are sensitive to variation of the fine-structure constant (alpha) due to relativistic corrections of opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a rf electric-dipole transition between them. Our measurements show that the frequency variation of the 3.1-MHz transition in (163)Dy and the 235-MHz transition in (162)Dy are 9.0+/-6.7 Hz/yr and -0.6+/-6.5 Hz/yr, respectively. These results provide a rate of fractional variation of alpha of (-2.7+/-2.6) x 10(-15) yr(-1) (1 sigma) without assumptions on constancy of other fundamental constants, indicating absence of significant variation at the present level of sensitivity.     

Acousto-mechanical and thermal properties of clotted blood

The efficacy of ultrasound-assisted thrombolysis as an adjunct treatment of ischemic stroke is being widely investigated. To determine the role of ultrasound hyperthermia in the process of blood clot disruption, the acousto-mechanical and thermal properties of clotted blood were measured in vitro, namely, density, speed of sound, frequency-dependent attenuation, specific heat, and thermal conductivity. The amplitude coefficient of attenuation of the clots was determined for 120 kHz, 1.0 MHz, and 3.5 MHz ultrasound at room temperature (20 +/- 2 degrees C). The attenuation coefficient ranged from 0.10 to 0.30 Np/cm in porcine clots and from 0.09 to 0.23 Np/cm in human clots. The experimentally determined values of specific heat and thermal conductivity for porcine clotted blood are (3.2 +/- 0.5) x 10(3) J/kg x K and 0.55 +/- 0.13 W/m x K, respectively, and for human clotted blood are (3.5 +/- 0.8) x 10(3) J/kg x K and 0.59 +/- 0.11 W/m x K, respectively. Measurements of the acousto-mechanical and thermal properties of clotted blood can be helpful in theoretical modeling of ultrasound hyperthermia in ultrasound-assisted thrombolysis and other high-intensity focused ultrasound applications.     

Measurement of the asymmetry in the decay Omega+-->LamdaKappa+-->rhopi+Kappa+

The asymmetry in the rho angular distribution in the sequential decay Omega+-->LamdaKappa+-->rhopi+Kappa+. has been measured to be alphaOmegaalphaLamda=[+1.16+/-0.18(stat)+/-0.17(syst)]x10(-2) using 1.89x10(6) unpolarized Omega+ decays recorded by the HyperCP (E871) experiment at Fermilab. Using the known value of alphaLamda, and assuming that alphaLamda=-alphaLamda, alphaOmega=[-1.81+/-0.28(stat)+/-0.26(syst)]x10(-2). A comparison between this measurement of alphaOmegaalphaLamda and recent measurements of alphaOmegaalphaLamda made by HyperCP shows no evidence of a violation of CP symmetry.