Measurement of the astrophysical S factor for dd interaction at ultralow deuteron-collision energies using the inverse Z pinch

This paper is devoted to measurement of the astrophysical S factor and cross sections of the d + d → ³He + n reaction at ultralow deuteron-collision energies. Formation of the flow of the accelerated deuterons incident on the CD₂ solid-state target was made within the scheme of the inverse Z pinch. The liner in the initial state was a hollow supersonic deuterium jet of radius of 15 mm and length of 20 mm. The experiment was carried out at the pulsed high-current accelerator (I=950 kA, τ=80 ns) of the Institute of High-Current Electronics (Tomsk, Russia). Measurement of the deuteron energy distribution was performed through an analysis of the time distributions of the intensity of the liner radiation (H_α and H_β lines) generated during the liner radial movement from the axis. Recording of this radiation was carried out by optical detectors placed along the direction of the liner moving from its axis. The measured value of the astrophysical S factor for the dd reaction at the average deuteron collision energy E _coll=3.69 keV was equal to S(E _coll=3.69 keV)=58.2±18.1 keV b. The dd-reaction cross section calculated using the found value of the S factor and known representation of the reaction cross section as the product of the barrier factor and the astrophysical S factor was σ _dd ⁿ (E _coll=3.69 keV)=(1.33±0.41)×10^?30 cm².     

Neutrino-induced deuteron disintegration in an experiment at the Krasnoyarsk nuclear reactor

The results of studying antineutrino interactions with deuterons (CCD and NCD reactions) and hydrogen (CCP) at the Krasnoyarsk underground reactor with the Deuteron detector are presented. The cross sections for NCD and CCD were measured with a precision of 9%. For CCP, the precision is 3%: σ _expt ^NCD =(3.35±0.31)×10^?44 cm²/fission ²³⁵U, σ _expt ^NCD =(1.08±0.09)×10^?44 cm²/fission ²³⁵U, and σ _expt ^NCD =(6.39±0.19)×10^?43 cm²/fission ²³⁵U. The precision of the experimental results is close to the theoretical one and is in good agreement with other experiments. The limit on the parameters of antineutrino oscillations into the sterile state was obtained: Δm ²≤4.7×10^?2 eV² for sin²(2?)=1.0 (68% C.L.). A comparison of the measured and theoretical cross section gives us the neutron-neutron scattering length of a _nn(S)=?17±6 fm in the approach of zero momentum transfers. The weak neutral current constant is in good agreement with the prediction of the Standard Model: G _A ^NC =G _A ^CC /0.932±0.056.     

Lebensdauer- und Hyperfeinstrukturmessungen an einigen angeregten Zuständen der Konfiguration 4d 9 5p im Pd I-Spektrum mit der Level-crossing-Methode

Lifetimes and hfs coupling constants of some excited states of the 4d ⁹ 5p configuration of Pd I have been determined in a level crossing experiment by observing the field dependence of the polarization of the fluorescence radiation in a magnetic field. From the halfwidths of the measured zero field level crossing signals one obtains the mean lifetimes of the following fine structure states:τ(³P ₁ ⁰ )=(7.46±0.32)nsec;τ(³ P ₂ ⁰ )=(6.9±0.76)nsecτ(³P ₁ ⁰ )=(4.99±0.35)nsec;τ(³ D ₁ ⁰ )=(4.89±0.40)nsecτ((³D ₃ ⁰ )=(6.99±0.49)nsec;τ(³ F ₄ ⁰ )=(7.09±0.46)nsec.Δm=2 crossing signals were detected in the³ P ₁ ⁰ ,³D ₃ ⁰ and³F ₄ ⁰ -states of the odd isotope¹⁰⁵Pd. A detailed analysis of the experimental curves yields the hfs coupling constantsA andB of these states:A(³P ₁ ⁰ )=?(133±2) Mc/sec;B(³ P ₁ ⁰ )=(140±30) Mc/secA(³D ₃ ⁰ )=?(120±10) Mc/sec;B(³ D ₃ ⁰ )=?(660±100) Mc/secA(³F ₄ ⁰ )=?(87±2) Mc/sec;B(³ F ₄ ⁰ )=?(330±30) Mc/sec. A theoretical calculation of the hfs constants is given on the basis of reduced matrix elements. Within the limit of the errors these values agree with the experimental ones. The nuclear electric quadrupole moment deduced from the measuredB values isQ (¹⁰⁵Pd)=(0.8±0.3)·10^?24 cm² (without corrections).     

Analysis of average primary gamma-transition intensities and cross sections of the113Cd(n, γ) reaction

A combined analysis of the available data on the primaryγ-ray intensities from the¹¹³Cd(n, γ) reaction atE _n=1.9 and 24.3 keV neutron energies together with the data on¹¹³Cd neutron capture cross sections in theE _n=3–200 keV energy region was carried out. The neutron strength functions were determined asS _n0=(0.260±0.073) 10^?4 and S_n1=(5.06±0.67) 10^?4. No spin-orbit splitting of thep-wave neutron strength function was found. The energy dependence of theE 1 radiative strength function {ie147-01} was fitted by the Kadmenski-Furman model somewhat better than by a standard Lorentzian. TheM 1 giant resonance parameters were obtained as E _G ^{M 1} =8.8±1.6 MeV and Γ _G ^{M 1} = 4.7±2.6 MeV. The neutron capture cross section of¹¹³Cd from its isomeric state ({ie147-02}=11/2^?, E ₁ ^m =263.7 keV) was calculated.     

Production and loss of N 2 + , Ne+ and Ne 2 + during the decay period of plasmas produced in neon-nitrogen mixtures

Studies of the time dependencies of the number density of N ₂ ⁺ , Ne⁺ and Ne ₂ ⁺ ions have been made during the decay period of plasmas produced in neon containing various concentrations of nitrogen molecules. Reaction rate constants were obtained for N ₂ ⁺ +N₂+Ne→N ₄ ⁺ +Ne((1.2±0.2)×10^?29 cm⁶ sec^?1) and Ne⁺+N₂→N ₂ ⁺ + Ne ((2.9±0.3) × 10^?12 cm³ sec^?1). The ambipolar diffusion coefficient of N ₂ ⁺ in neon was found to beD _a p _o =350±20 cm² sec^?1 Torr.     

MeanM-subshell fluorescence yields atZ=88, 90, 92, and 94

M x-ray —L x-ray coincidence measurements with high resolution, cooled Si(Li) x-ray detectors were made on transitions following the alpha decays of²²⁸Th,²³²U,²³⁸Pu, and²⁴⁴Cm, in order to determine the meanM-subshell fluorescence yields. The values obtained are:v ₄ ^M =0.032±0.002, andv ₅ ^M =0.024±0.002 atZ=88;v ₁ ^M =0.038±0.003,v ₄ ^M =0.042±0.002, andv ₅ ^M =0.038±0.002 atZ=90;v ₁ ^M =0.047±0.002,v ₄ ^M =0.048±0.002, andv ₅ ^M =0.044±0.002 atZ=92;v ₁ ^M =0.066±0.002,v ₄ ^M =0.062±0.002, andv ₅ ^M =0.063±0.002 atZ=94. The quantityΩ ₁ ^M +f ₁₂ ^MΩ ₂ ^M was measured as (56±10)×10^?4, (62±12)×10^?4, (99±18) ×10^?4, and (93±15)×10^?4 forZ=88, 90, 92, and 94, respectively, which agree well with the calculations of McGuire. The radiativeL ₁-L ₃ transition intensity was measured for the four atomic numbers and found to be consistently less than the calculations of Scofield by about 45 percent.     

Temperature dependence of Mn2+ EPR in Sn2P2S6 near the phase transition

The X-band EPR spectrum of Mn²⁺ in Sn₂P₂S₆ was studied in the temperature rangeT=223–363 K. At room temperature the spin-Hamiltonian constants areg=2.00±0.01,B ₂ ⁰ =(163±3)·10^?4 cm^?1,B ₂ ² =(159±3)·10^?4 cm^?1,A=?(75±1)·10^?4 cm^?1. The effect of the invariance in temperature of the resonance magnetic fields in the narrow temperature rangeT=337–340 K and the model of the paramagnetic centre are discussed. According to EPR data a phase transition occurs atT=337 K. This transition from the paraelectric phase to the ferroelectric one is accompanied by a dramatic change in value of the spin-Hamiltonian constantB ₂ ⁰ .     

Photoinduced electron transfer in meso-nitrophenyl-substituted porphyrins and their chemical dimers

It is shown that steric interactions of volume substituents in the β-positions of pyrrole rings and the nitro group in mono-and di-meso-phenyl-substituted of octaethylporphyrins and their chemical dimers containing the electron-acceptor NO₂ group in the ortho-position of the phenyl ring at 295 K favor the direct overlap of molecular orbitals of the interacting subunits, resulting in the efficient quenching of fluorescence due to the direct electron transfer from the S₁ level to the lower-lying state via the “through-space” mechanism. The electron transfer in these compounds in nonpolar media (the rate constant k _et ^S =(3.2–9.5)×10⁹ s^?1 is nonadiabatic, whereas in strongly polar solvents (k _et ^S =2×10¹¹ s^?1) the adiabatic effects can be manifested. In compounds containing the NO₂ group in meta-or para-positions of the phenyl ring, the nonadiabatic electron transfer from the S ₁ level occurs less efficiently both in polar [k _et ^S =(0.2–5)×10¹⁰ s^?1] and nonpolar media [k _et ^S =(0.1–1.0)×10⁷ s^?1]. In this case, the electron transfer involves molecular orbitals of phenyl (the “through-bond” mechanism), and its efficiency depends on the orbital electron density in the meta-and para-positions of the phenyl ring. Based on the experimental data obtained and analysis of the electron transfer within the framework of the Marcus theory, the energy scheme of relaxation processes of the electronic energy in the compounds under study involving charge transfer states is suggested.     

K-capture probabilities in the electron capture decay of159Dy

TheK-electron capture probabilities (P _k) for the 58 keV state and the ground state of¹⁵⁹Tb in the decay of¹⁵⁹Dy have been determined. The measured values,P _k ⁵⁸ =0.81±0.05 andP _k ⁰ =0.79±0.06 are found to be in excellent agreement with theoretical results.     

Charged particle and π0 multiplicity distributions and the annihilation properties of\bar p p interactions at 70 GeV/c

The elastic and inelastic \(\bar p\) p cross sections at 70 GeV/c have been determined in an experiment performed at CERN using BEBC equipped with a TST. The topological cross sections were measured and the moments of the inelastic multiplicity distribution are 〈n _c 〉=6.16±0.09, 〈n _c 〉/D=2.04±0.05 andf ₂ ^cc =2.97±0.03. The average number of Dalitz pairs per inelastic event is (3.12±0.09)×10^?2. Assuming that these all arise from π⁰ decay the average π⁰ multiplicity is \(\langle n_{\pi ^0 } \rangle = 2.71 \pm 0.14\) . The \(\bar p\) p?pp cross section differences lead to an annihilation cross section σ _A = 4.42±0.41 mb and the moments of the annihilation multiplicty distribution are 〈n _A 〉=8.0±0.3, 〈n _A 〉/D=2.5±0.2 andf ₂ ^A?? =?1.4±0.3. An independent check of σ _A was made by investigating fast forward charged and neutral secondary interactions in the TST and in the surrounding neon-hydrogen mixture, and gives a value σ _A = 5.0±1.6 mb. The ratio of fast \(\bar n\) to \(\bar p\) production in non-annihilation interactions at 70 GeV/c is found to be 0.45±0.11.     

Preliminary results of the study of the d(d,n)3He reaction in the astrophysical energy range with the use of a Hall plasma accelerator

The possibility of using a plasma accelerator based on a pulsed Hall ion source to study the characteristics of pd, dd, d³He, ³He, and⁴He reactions in the astrophysical energy range (2–12 keV) has been considered. The preliminary experimental data on measurement of the astrophysical S factor for the dd reaction (dd → ³He + n (2.5 MeV)) at average deuteron collision energies E _col = 4.5 and 4.95 keV and the deuteron beam energy spread FWHM = 18% are reported. The found value of the S factor is in agreement with the results of the experiments carried out by us previously using linear plasma in the inverse Z-pinch configuration.     

Resonant absorption of the γ-radiation from the22Ne(p, γ)23Na reaction and the effect of rutherford scattering in the target on the width of the absorption curves

Gamma rays of energy 9.404 and 9.700 MeV were obtained from the reaction²²Ne(p, γ)²³Na at proton energies of 640 and 950 keV respectively and were resonantly absorbed in sodium metal. Isotopically separated²²Ne targets on nickel backings were used. The following level widths for²³Na were obtained: The 9.404 MeV level: Γ=65 ±40eV Γ_γ=2.2±0.7eV. The 9.700 MeV level: Γ=9.5 _?1.0 ^{+4.5 eV} Γ_γ=5.6 _?0.8 ^{+1.2 eV} . The disagreement between the results for the 9.404 MeV level and the previously determined values can probably be ascribed to proton scattering in the window of the gas target used in the latter measurement.     

Astrophysical <Emphasis Type="Italic">S</Emphasis>-factor of T(<Superscript>4</Superscript>He, γ)<Superscript>7</Superscript>Li reaction at <Emphasis Type="Italic">E</Emphasis><Subscript>cm</Subscript> = 15.7 keV

The astrophysical S-factor of the reaction T(⁴He, γ)⁷Li is measured for the first time at the center of mass energy E _cm = 15.7 keV, lower than the energy range of the Standard Big Bang Nucleosynthesis (SBBN) model. The experiment is performed on a Hall pulsed accelerator (TPU, Tomsk). An acceleration pulse length of 10 μs allows one to suppress the background of cosmic radiation and the ambient medium by five orders of magnitude. A beam intensity of ~ 5 × 10^{14 4}He⁺ ions per pulse allows one to measure an extremely low reaction yield. The yield of γ-quanta with the energies E _γ ⁰ = 2483.7 keV and E _γ ¹ = 2006.1 keV is registered by NaI(Tl) detectors with the efficiency ε = 0.331 ± 0.026. A method for direct measurement of the background from the chain of reactions T(⁴He, ⁴He)T→T(T, 2n)X→(n, γ) and/or (n, n′γ) which ends by neutron activation of materials surrounding the target is proposed and implemented in this study. The value of the astrophysical S-factor of the reaction T(⁴He, γ)⁷Li S _αt (E _cm = 15.7 keV) = 0.091 ± 0.032 keV b provides the choice from the set of experimental data for the astrophysical S _αt -factor in favor of experimental data [4] with S _αt (E _cm = 0) = 0.1067 ± 0.0064 keV b.     

Absolute cross sections of electron attachment to molecular clusters: Part I. Formation of (CO2) N −

A procedure of determining absolute cross section σ^? of electron attachment to (CO₂)_N clusters at pair collisions in crossed beams is suggested. The cross section is measured as a function of energy (E = 0.1–50 eV) and of cluster mean size N in a beam $(\bar N = 2 - 4000 molecules)$ . It is found that, even at $\bar N > 200$ and E ≤ 3 eV, σ^? is equal to, or larger than, 7 × 10^?13 cm², i.e., by more than one order of magnitude exceeds the maximal cross section of CO₂ ionization by electron impact. The dependences σ^? $(\bar N,E)$ have two wide continua at E ≤ 5.2 eV and E ≥ 6.9 eV, which correlate well with known functions of CO₂ electron-impact-induced excitation. These continua are attributed largely to formation of (CO₂) _N ^? ions during electron thermalization and solvation in the clusters. At E → 0, the polarization capture of an incident electron by the cluster leads to a sharp increase in cross section σ^?(E). From the dependences σ^? $(\bar N,E)$ measured, the thermalization and sovation probabilities for electrons with E ≤ 0.8 eV and the rate of electron energy loss in the cluster are found.     

Resonance strengths,branching ratios and mean lifetimes of nuclear energy levels in23Na

The gamma decay of the²²Ne(p, y)²³Na resonances in the proton energy rangeE _p=1.0→2.0 MeV has been investigated with a 20cm³ Ge(Li) detector. Implanted targets were used. The absolute strengths of the strongest resonances were determined and the branching ratios of twenty resonance levels and several bound states are reported. Mean lifetimes of the levels atE _x=2.078 MeV (18.7±3.5 fs), 2.393 MeV (580 _?190 ⁺³⁷⁰ fs), 2.641 MeV (88 _?14 ⁺²⁰ fs), 2.985 MeV (4.0 _?1.0 ^+1.3 fs), 3.679 MeV (24 _?4 ⁺⁵ fs), 3.915 MeV (7.4 _?2.0 ^+2.5 fs) and 4.775 MeV (<2.0 fs) were obtained from measurements of the gamma ray Doppler shifts.     

A preciseB(E2) for the first 2+ state in52Cr

A resonance fluorescence self-absorption experiment has been carried out for the 1,434 MeV first excited state in⁵²Cr, using gaseous⁵²MnI₂ as source for the exciting gamma radiation. TheB(E2,0 ₁ ⁺ →2 ₁ ⁺ )=(687±13)e ² fm⁴ is in agreement with the most recent Coulomb excitation and inelastic electron scattering experiments yielding (660±30)e ² fm⁴ and (634±39)e ² fm⁴, respectively, and disagrees with former electron scattering experiments.     

Recurrence of random walks in the Ising spins

Consider the 1/2-Ising model inZ ². Let σ _j be the spin at the site (j, 0)∈Z ² (j=0, ±1, ±2, ...). Let \(\{ X_n \} _{n = 0}^{ + \infty } \) be a random walk with the random transition probabilities such that $$P(X_{n + 1} = j \pm 1|X_n = j) = p_j^ \pm \equiv 1/2 \pm v(\sigma _j - \mu )/2$$ We show a case whereE[p _j ⁺ ≧E[p _j ^? ], but \(\mathop {\lim }\limits_{n \to \infty } X_n = - \infty \) is recurrent a.s.     

ΛΛ 6 He and Λ 9 Be systems in the three-body cluster model treated on the basis of differential Faddeev equations

The _ΛΛ ⁶ He and _Λ ⁹ Be hypernuclei are treated as the S=0, T=0 (for the former) and S=1/2, T=0 (for the latter) bound states of the three-cluster systems ΛΛα and Λαα, respectively. The cluster-reduction method is used to solve the s-wave differential Faddeev equations for these systems. On the basis of the MT I–III model, the ΛΛ interaction potential is specified in the form $V_{\Lambda \Lambda } = \frac{2}{3}V_{NN} $ . Phenomenological potentials are used to describe Λα and αα interactions. The binding energies of the _ΛΛ ⁶ He and _Λ ⁹ Be hypernuclei and the parameters of low-energy Λ-hyperon and α-particle scattering on a _Λ ⁵ He hypernucleus are calculated. It is shown that the proposed ΛΛ interaction potential makes it possible to reproduce faithfully the binding energy of the _ΛΛ ⁶ He hypernucleus and that scattering in the Λ _Λ ⁵ He system is similar to neutron scattering on a deuteron.     

Observation and analysis ofE mesons in\bar p p annihilation at rest in H2 gas

Antiproton-proton annihilation at rest in a gaseous H₂ target at NTP into the final state π⁺ π^? K ^± π^? (K ⁰) with an undetectedK ⁰ or \(\bar K^0 \) has been investigated. We observe theE(1420) resonance in the invariant mass spectrum (K ⁰)_miss K ^± π^? with massM _E =1413±8 MeV/c² and widthГ ^E =62 ± 16MeV/c² and find evidence for the production of thef ₁(1285). The absolute branching ratio of \(\bar p\) p → π⁺ π^? E ⁰,E ⁰ →K ₀ ^L K ^± π ^? at (61±6)%P wave annihilation is (3.0±0.9)·10^?4 of all annihilations. The observed suppression of theE production fromP wave with respect to theS wave together with some simple selection rules suggest that the quantum numbers of theE(1420) areJ ^pc=0^?+ and not I⁺⁺.