Measurement of thes-wave contribution to 2p-level shifts in pionic atoms

Energies and widths of pionic 3d-2p transitions of₃₀Zn,₃₂Ge, and₃₃As have been measured with a Ge detector. The values of the 2p shifts obtained from the measurementε _2p (Zn)=7.0±1.4keV,ε _2p (Ge)=5.5±0.9keV, andε _2p (As)=4.6±0.9keV show a decreasing behaviour for largeZ, which is caused by an increasings-wave contribution as predicted by theory.     

X-rays from pionic 3He

Pionic X-ray energies, lorentzian widths, and relative intensities have been measured for the transitions in liquid ³He. The pion-nucleus interaction is found to result in an attractive shift of the 1s level of 27 ± 5 eV and in a lorentzian width of 65 ±12 eV. The measured K_β to K_α intensity ratio is 1.05±0.07.     

Pionic and muonic X-ray transitions in liquid helium

Energies and intensities of pionic and muonic X-rays in liquid ⁴He have been measured with a Si (Li) detector. The energy shift due to strong interaction effects of the pionic 1s level in ⁴He was determined to be ?75.7±2.0 eV. The natural line width of this level is 45±3 eV. These values are compared with different theoretical predictions. Cascade calculations, including external Auger effect and sliding transitions, have been performed to reproduce the yields of the muonic and pionic transitions. The pionic 2p level width is deduced: $\text{Γ}{}_{\mathrm{<mtext>2</mtext><mtext>p</mtext>}}\text{= (1.1 ± 0.5) × 10}{}^{12}\text{sec}{}^{\mathrm{?1}}\text{=}\text{(7.2±3.3) × 10}{}^{\mathrm{?4}}\text{eV}$.     

对40Ca9.5—10.5MeV能区内几组核能级宽度的测量

本文介绍了用γ共振吸收法测量⁴⁰Ca 9603.9keV,10321.0keV两组能级和9864.6,9868.8keV一组双重态能级的能级宽度,选用³⁹K(p,γ)反应所放出的γ射线激发相应的⁴⁰Ca吸收核能级。对于9603.9keV,10321.0keV的能级宽度,这里给出了比较精确的结果,相应的能级宽度分别为Γ=188±47eV,Γ=91±15eV。对于9864.6,9868.8keV能级,结果为Γ=100±24eV,Γ=899±214eV,由于⁴⁰Ca 9864.6,9868.8keV两能级靠得很近,因此这里用γ共振吸收法测量它们的能级宽度与以往有所不同,将同时有两组γ射线用来激发同样两个能级而发生交叉激发。我们对相应的实验处理方法作了推广。此外,用(p,γ)共振产额法测量了⁴⁰Ca 9603.9keV,10321.0keV能级宽度,得到了与γ共振吸收法一致的结果。本文还对⁴⁰Ca 9603.9keV,10321.0keV能级的(p,γ)共振强度S_pγ、同位旋T等进行了讨论。 关键词：     

Chiral symmetry probed with pionic atoms

Study of pionic atom has been revisited by a recent discovery of deeply bound pionic states in the context of possible sensitivity to the partial chiral restoration in the nuclear medium. Precisely measured binding energies and widths of the deeply bound π^? Is states in ^115,119,123Sn in ^116,120,124Sn(d,³He) reactions at recoil-free conditions are used to deduce the medium-modified isovector scattering amplitude as b₁ = 0.115 ± 0.007m _π ^?1. The observed enhancement of b ₁ over the free πN value infers 34% reduction of $\left\langle {\bar qq} \right\rangle $ at the normal nuclear density, ρ = 0.17 fm^?3.     

X-rays from antiprotonic helium in helium gas

X-ray transitions to the 4F, 3D, and 2P atomic levels of p?He have been observed with antiprotons stopped in He gas at 4 and 1.1 atm NT. The population by radiative transitions of the 3D level in gas Y_M(4atm) = (28±14)% and Y_M(1.1 atm) = (43±22)% exceeds by more than one order of magnitude that measured in liquid He. The annihilation width of the 3D level Γ^a_3D = 2.8±1.0 × 10^?3eV is determined from the ratio between the numbers of X-rays feeding and depopulating the 3D level. The strong-interaction shift of the 2P level ε(2P) = ?14±6 eV is obtained by inputting the $\text{p}\text{He}$ experimental X-ray yields into a cascade calculation, the results of which are in good agreement with well-established data from muonic, pionic, and kaonic helium.     

Quadrupole interactions in pionic and muonic tantalum and rhenium

The hyperfine splitting of pionic and muonic X-rays in natural Re has been studied using the known ratio (accurate to 1.6 parts in 10⁵) of the quadrupole moments of the two naturally occurring ¹⁸⁵Re and ¹⁸⁷Re isotopes. From the hyperfine splitting of the ⁵g → 4f and 4f → 3d pionic X-rays the effective quadrupole hyperfine constants were determined to be ¹⁸⁷A₂^eff(4f) = 1.163 ± 0.010 keV and ¹⁸⁷A₂^eff(3d) = 5.39 ± 0.63 keV, giving strong interaction quadrupole shifts ₂(4f) = 46 ± 10 eV and ₂(3d) = 1.3 ± 0.6 keV. The strong interaction monopole shifts ₀ and widths Γ₀ of the 5g, 4f and 3d levels have also been measured. For the two higher orbits, standard optical-potential calculations fit the measured shifts and widths quite well. The observed deeper-lying 3d state, however, has shifts and widths that differ by a factor of 2 or more from the predictions. From the measured quadrupole hyperfine constants of the 4f level we calculate the spectroscopic quadrupole moments to be ¹⁸⁷Q^μ(gm) = 2.09 ± 0.04 b, ¹⁸⁷Q^π = 2.07 ± 0.02 b, ¹⁸⁵Q^μ = 2.21 ± 0.04 b, and ¹⁸⁵Q^π = 2.1 addition, muonic X-rays from ¹⁸¹Ta were observed; using the same methods for determining the quadrupole moment as above, a value of ¹⁸¹Q^μ = 3.28 ± 0.06 b was obtained, in good agreement with earlier published data.     

Spectroscopic quadrupole moment of holmium from pionic X-ray measurement

From the observed quadrupole splitting of the 5g-4f X-ray transition in π-¹⁶⁵Ho we determine the spectroscopic quadrupole moment of ¹⁶⁵Ho to be Q = 3.47±0.11 b. The strong interaction shift and the width of the 4f level are found to be ?₀ = 0.35±0.08 keV and Γ₀ = 0.21±0.04 keV, respectively.     

The pionic hydrogen experiment at PSI

A new high-precision determination of the strong-interaction shift (∈_1s) and broadening (Γ_1s) of the ground state in pionic hydrogen (πH) has been started at PSI. This constitutes a direct measurement of the πN scattering lengths and is an important test of the methods of chiral perturbation theory.The experiment will be conducted in two steps. In the first step we aim for a precision of 0.2% for ∈_1s and 3% for Γ_1s. A new method of energy calibration is used: by measuring πH simultaneously with pionic oxygen (πO), systematic errors are suppressed. The goal for the second step is an accuracy of 1% for Γ_1s.     

Measurement of pionic and muonic X-rays IN B

The energies of muonic 2p-1s X-rays in ¹⁰B and ¹¹B have been measured to be 52217(8) eV and 52279(5) eV, from which the rms nuclear charge radii were calculated to be 2.44(6) fm and 2.38(4) fm. The energies and widths of pionic 2p-1s X-rays have been measured in ¹⁰B to be 65901(13) eV and 1780(30) eV, and in ¹¹B to be 65120(26) and 1720(80) eV. The sensitivity of the strong interaction shift to the neutron matter distributions has been investigated using an optical-model approach. The results of these calculations are not in good agreement with the experimental results when reasonable values of the nuclear matter distributions are used.     

Experimental determination of the electron screening potential energy for the d(d, n)3He Reaction in ZrD2 and D2O in the ultralow energy region

This work is devoted to measuring of the values of the astrophysical S-factors and electron screening potential energy for a d(d,n)³He reaction occurring at ultralow energies in zirconium deuteride ZrD₂ (3.5–7.0 keV) and heavy water D₂O (2.2–6.0 keV). The experiment was performed on the Hall pulsed plasma accelerator at the TPU Nuclear Physics Institute (Tomsk) with ZrD₂ and D₂O targets produced by the magnetron sputtering of zirconium in a deuterium environment and heavy water freezing-out on a copper support, respectively. A χ ² analysis of the dependence of the neutron yields and astrophysical S-factors for the dd reaction on the deuteron collision energy E revealed that the upper bounds of the electron screening potential energy for interacting deuterons in ZrD₂ and D₂O and of the astrophysical S-factors at the deuteron collision energy E = 0 were U _e (ZrD₂) < 30 eV, U _e (D₂O) < 25 eV, S(0) = (57.2 ± 3.9) keV · b (ZrD₂), S(0) = (58.6 ± 3.6) keV · b (D₂O) at the 90% confidence level.     

The 16O + p → 17F (T = 32) resonances at Ep = 11.26,12.71 and 14.57 MeV

Excitation functions for ¹⁶O+p reactions have been measured with high energy resolution in the region of the first, second and seventh $\text{T =}\text{3}\text{2}$ resonances in ¹⁷F at extreme backward angles. The observed resonance shapes have been analyzed with a single-level resonance formula taking the off-resonance spin-flip amplitude into account. The resonance parameters of the ¹⁷F first $\text{T =}\text{3}\text{2}$ state studied with special emphasis are E_x = 11193.3 ± 2.3 keV, Γ = 200 ± 40 eV and Γ_p0 = 19 ± 3 eV. This result and other results are compared with previous studies and theoretical predictions. The comparison with data of the mirror nucleus ¹⁷O is discussed with respect to the observed charge asymmetry of the isospin-forbidden particle decay widths.     

Resonant neutron capture in 40Ca

The neutron capture cross section of ⁴⁰Ca has been measured with ≈ 0.2 % energy resolution below E_n = 300 keV. Resonance parameters have been extracted for many new p- and d-wave resonances. Gamma-ray spectra were also measured following capture in one doublet and two resolved resonances below 50 keV. Strong feeding of low-lying p-wave levels was observed in all cases. Calculations showed that valence transitions were inadequate to account for the observed dominance of these transitions and a further mechanism is required. The average resonance parameters obtained from the data are as follows: 〈D〉 = 37 + 4keV, 10⁴S₁ = 0.16 ± 0.05, 10⁴S₂ = 2.0 ± 0.7. The average radiative widths and standard deviations of their distributions were found to be strongly l-dependent as follows: 〈Γ_γ〉_s = 1.5 ± 0.9 eV, 〈Γ_γ〉_p = 0.36 ± 0.09 eV and 〈Γ_γ〉_d = 0.7 ± 0.4 eV.     

Measurement of astrophysical S factors and electron screening potentials for d(d, n)3He reaction In ZrD2, TiD2, D2O, and CD2 targets in the ultralow energy region using plasma accelerators

The paper is devoted to study electron screening effect influence on the rate of d(d, n)³He reaction in the ultralow deuteron collision energy range in the deuterated polyethylene (CD₂), frozen heavy water (D₂O) and deuterated metals (ZrD₂ and TiD₂). The ZrD₂ and TiD₂ targets were fabricated via magnetron sputtering of titanium and zirconium in gas (deuterium) environment. The experiments have been carried out using high-current plasma pulsed accelerator with forming of inverse Z pinch (HCEIRAS, Russia) and pulsed Hall plasma accelerator (NPI at TPU, Russia). The detection of neutrons with energy of 2.5MeV from dd reaction was done with plastic scintillation spectrometers. As a result of the experiments the energy dependences of astrophysical S factor for the dd reaction in the deuteron collision energy range of 2?C7 keV and the values of the electron screening potential U _e of interacting deuterons have been measured for the indicated above target: U _e (CD₂) ? 40 eV; U _e (D₂O) ? 26 eV; U _e (ZrD₂) = 157 ± 43 eV; U _e (TiD₂) = 125±34 eV. The value of astrophysical S factor, corresponding to the deuteron collision energy equal to zero, in the experiments with D₂O target is found: S _b (0) = 58.6 ± 3.6 keV b. The paper compares our results with other available published experimental and calculated data.     

Ionic conductivity of solid lithium iodide and its monohydrate

The solid electrolytes LiI, LiI,H₂O and LiI,D₂O have been characterized by ac- and dc-conductivity measurements. LiI exhibits two conductivity regions: an extrinsic below ≈ 180°C and an intrinsic above, with activation energies of 0.43±0.04 eV and 0.81±0.05 eV respectively. The room temperature conductivities of the hydrates LiI,H₂O and LiI,D₂O are 6.6× 10^?6 and 6.1×10^?6 (Ω cm)^?1 respectively. The activation energy for Li-ion motion in LiI,D₂O is 0.66±0.05 eV.     

Pionic x-rays and the neutron radius of 44Ca

Differences between strong interaction level shifts and widths for 2p states in pionic atoms of ^44,40Ca have been measured. Analysis in terms of an effective pion-nucleus potential leads to a difference in neutron rms radii of r_n(44)?r_n(40) = 0.05 ± 0.05 fm.     

Half lives of the 482.2 keV and 615.3 keV levels in181Ta

The half lives of the excited levels at 482.2 keV and 615.3 keV in¹⁸¹Ta have been measured by the delayed coincidence technique. In the nanosecond time range (482.2 keV level) the most serious sources of errors are jitter, walk and drift phenomena. To minimize those the time pick-off has been defined carefully by means of modern fast timing detectors and electronics. In the microsecond time range (615.3 keV level) the ratio of true delayed coincidences to chance coincidences influences considerably the final accuracy of the half-life measurements. It has been reduced as much as possible. From a series of independent measurements half lives ofT _1/2=(10.67±0.05) ns andT _1/2=(17.64±0.14) μs have been deduced for the 482.2 keV and 615.3 keV levels, respectively. The results have been compared with other values published before.     

Properties of excited levels in102Rh by the102Ru(p,nγ) reaction

The level scheme of¹⁰²Rh has been investigated by the¹⁰²Ru(p, nγ) reaction in the proton energy range 3.1 MeV≦E _p≦6 MeV. Excitation functions,γ-γ coincidences and pulsed beam measurements have been performed and a level scheme including 33 excited states up toE _x≈650 keV has been constructed. Theγ-branchings of several levels have also been measured. The lifetimes of 5 excited states have been determined with the centroid-shift method:τ _m(105.2 keV)=(1.3±0.3) ns,τ _m(123.7 keV)=(0.6±0.3) ns,τ _m(178.6 keV)=(1.5±0.3) ns,τ _m(208.7 keV)=(0.5±0.3) ns,τ _m(359.6 keV)=(0.8±0.4) ns. Upper limits have been placed for the lifetimes of 20 other levels.