Der Zerfall des Cu60

Theγ-ray-spectrum of Ni⁶⁰ associated with the E.C.- and β⁺-decay of Cu⁶⁰ has been measured with Ge(Li)-crystals. The observedγ-ray-transitions led to a new levelscheme for this decay with Ni⁶⁰-levels at: 1332, 2159, 2286, 2627, 3125, 3196, 3272, 3391, 4025, 4080, 4332, 4500, 4554 and 4584 keV, most of them could be identified with previously reported levels found in scattering experiments. As far as possible spin and parity assignments have been made, and the levels are compared with phonon and quasi-particle theory.     

Der Zerfall des Co56

Theγ-ray-spectrum of Fe⁵⁶ associated with the E.C.- andβ ⁺-decay of Co⁵⁶ has been measured with Ge(Li)-crystals. 6 newγ-ray-transitions have been found in this spectrum deexciting 3 new levels in Fe⁵⁶. The intensities of these transitions have been estimated and a new level-scheme is proposed. The new levels could be identified with some of previously reported levels found in Fe⁵⁶(p, p′)-measurements.     

Relativmessung integrierter Wirkungsquerschnitte für den Kernphotoeffekt: Die Reaktion O16(γ, n)O15

Li₂CO₃ and Na₂C₄H₈O₈ have been irradiated by 34 MeV bremsstrahlung. The yield of the induced O¹⁵ activity has been measured relative to the yield of the C¹²(γ, n)C¹¹ resp. Cu⁶³(γ, n)Cu⁶² reaction by detecting the annihilation quanta. Additional yield measurements with the bremsstrahlung beam attenuated by 18 mm of lead were made to determine the ratio of the integrated cross sections for the reactions O¹⁶(γ, n)O¹⁵ and C¹²(γ, n)C¹¹ resp. Cu⁶³(γ, n)Cu⁶². Using the cross section ofBarber et al. for C¹²(γ, n)C¹¹, the cross section integrated up to 33 MeV for O¹⁶(γ, n)O¹⁵ was obtained to 61±7 MeVmb.     

Der Zerfall des Ruthenium 95

Theγ-spectrum of Tc⁹⁵ associated with the E.C.- and β⁺-decay of Ru⁹⁵ has been measured with a Ge(Li)-counter and a NaJ-crystal. 12 newγ-ray transitions have been found in these spectrums. To propose a new level-schemeγ-γ-coincidences have been taken with 2 NaJ-crystals in a two-dimensional device. Besides this the total conversion coefficient of the 336 keV transition was measured by detecting the electrons in a Si(Li)-counter and theγ-rays in a NaJ-crystal.     

Untersuchungen über die Energieabhängigkeit von Kernreaktionen mit Neutronen im Energiebereich zwischen 12 und 19 MeV

Continuing earlier investigations we studied the energy dependence of the cross sections of the following nuclear reactions produced by neutrons in the energy range from 12 to 19 MeV: P³¹(n, 2n)P³², P³¹(n,α)Al²⁸, Cu⁶⁵(n, 2n)Cu⁶⁴, Cu⁶⁵(n, p)Ni⁶⁵, Zn⁶⁴(n, 2n)Zn⁶³, Zn⁶⁴(n, p)Cu⁶⁴, V⁵¹(n, p)Ti⁵¹, Br⁷⁹(n, α)As⁷⁶, O¹⁶(n, α)C¹³. The results were compared with cross sections calculated according to the statistical theory, considering the competition ofγ-ray emission and particle (predominantly neutron) emission from the excited residual nucleus.     

Structure of β-decay Strength Function <Emphasis Type="Italic">S</Emphasis><Subscript>β</Subscript>(<Emphasis Type="Italic">E</Emphasis>) in Halo Nuclei

It is shown that when the parent nucleus has nn Borromean halo structure, then after Gamow–Teller (GT) β^–-decay of parent state or after M1 γ-decay of Isobar Analogue Resonance (IAR) the states with np tango halo structure or mixed np tango + nn Borromean halo structure can be populated. Resonances in the GT β-decay strength function S_β(E) of halo nuclei, may have np tango halo structure or mixed np tango + nn Borromean halo structure. Correct interpretation of halo structure is important in experiments on β-decay study, interpretation of M1 γ-decay of IAR, and charge-exchange nuclear reactions analysis.     

Untersuchung des Vanadium-52-Zerfalls

Theγ-rays of the decay of V⁵² were investigated with NaJ crystals andγ-γ-cascades had been sought for by a fast-slow coincidence circuit. Threeγ-transitions of energyγ ₁=0,935 (0,14%),γ ₂=1,331 (0,9%),γ ₃=1,531 MeV (0,16%), respectively, in coincidence with the 1,434 MeV transition could be detected. It is concluded that there are four branches of V⁵² β-decay:β ₀=2,47MeV (98,8%, logft=5,1),β ₁=1,53 MeV (0,14%, logft=7,0),β ₂=1,14 MeV (0,9%, logft=5,7),β ₃=0,94 MeV (0,16%, logft=6,1). Spin and parity of V⁵² ground level is concluded to be 3+.     

Beta-decay strength measurement,total beta-decay energy determination,and dcay-scheme completeness testing by total absorption <Emphasis Type="Italic">γ</Emphasis>-ray spectroscopy

Applications of total absorption γ-ray spectroscopy and its combination with high-resolution nuclear spectroscopy methods for measurements of a β-decay strength function S _β (E), determination of the total β-decay energy Q _β , and testing of decay-scheme completeness are presented.     

Der Zerfall des Sr94

Using a mass spectroscopic device we have investigated theβ-decay of the short-lived fission product Sr⁹⁴. A strong 1·42 MeV-γ-radiation is found to be in coincidence with an allowedβ-decay of maximum energy of 2·1 MeV. The halflife of the decay is redetermined to 72±7 sec.     

Hyperfine nuclear interaction at copper lattice sites of high-temperature superconductors studied by <Superscript>61</Superscript>Cu(<Superscript>61</Superscript>Ni) Mössbauer emission spectroscopy

Mössbauer emission spectroscopy on the ⁶¹Cu(⁶¹Ni) isotope has been used to determine the quadrupole coupling constant C(Ni) and magnetic induction B(Ni) for the ⁶¹Ni²⁺ probe at copper sites in Cu₂O, CuO, La_{2 ?x}Ba_xCuO₄, Nd_2?xCe_xCuO₄, RBa₂Cu₃O₆, and RBa₂Cu₃O₇ (R=Y, Nd, Gd, Yb). The compounds containing divalent copper were found to exhibit linear C(Ni) vs. C(Cu) and B(Ni) vs. B(Cu) relations [C(Cu) and B(Cu) are the quadrupole coupling constant and magnetic induction for the ⁶³Cu probe, respectively, found by NMR], which is interpreted as an argument for the copper being in divalent state. The deviation of the data points corresponding to the Cu(1) sites in RBa₂Cu₃O₆ and RBa₂Cu₃O₇ from the C(Ni) vs. C(Cu) straight line may be due either to the copper valence being other than 2+ (in the RBa₂Cu₃O₆ compounds) or to the principal axes of the total and valence electric field gradient being differently oriented (in the RBa₂Cu₃O₇ compounds).     

Der Zerfall des Co55,T 1/2=18h

Co⁵⁵ T ^1/2=18 h) was produced by bombarding iron-foiles with 9 MeV deuterons.γ-spectra from the decay of Co⁵⁵ have been investigated using a scintillation fast-slow-coincidence circuit and a Li-drifted Ge-counter. 18γ-transitions were observed having the following energies in keV and intensities per Co⁵⁵-decay:γ ₁=95 (0.006),γ ₂=413 (0.016),γ ₃=475 (0.12),γ ₄=645 (0.005),γ ₅=750 (0.002),γ ₆=810 (0.025),γ ₇=900 (0.024),γ ₈=940 (0.80),γ ₉=985 (0.009),γ ₁₀=1055 (0.005),γ ₁₁=1210 (0.01),γ ₁₂=1320 (0.065),γ ₁₃=1375 (0.042),γ ₁₄=1410 (0.13),γ ₁₅=1600 (0.001),γ ₁₆=1800 (0.0006),γ ₁₇=2160 (0.001),γ ₁₈=2310 (0.0042).     

Der Spin des Grundzustandes von F20

The spin of the F²⁰-ground-state has been determined by means of a circularpolarisation correlation measurement on theΒ-γ-cascade of F²⁰. The experimental result gives spin 2 for the ground-state of F²⁰. Within the statistical error of the experiment theΒ-decay of F²⁰ has pure Gamow-Teller-interaction.     

Search for a super-allowed β−-decay of H4

If aβ-decaying H⁴ exists a super-allowed transition to the excited analogue state of He⁴ is possible. Such a decay mode was not considered in previous experiments. The reaction Li⁶ (γ, 2p) H⁴ was used to produce H⁴. No super-allowedβ ^?-decay of H⁴ could be observed and upper limits for the production cross section are given.     

Photoneutron reactions in astrophysics

Among key problems in nuclear astrophysics, that of obtaining deeper insight into the mechanism of synthesis of chemical elements is of paramount importance. The majority of heavy elements existing in nature are produced in stars via radiative neutron capture in so-called s- and r processes, which are, respectively, slow and fast, in relation to competing β ^?-decay processes. At the same time, we know 35 neutron-deficient so-called bypassed p-nuclei that lie between ⁷⁴Se and ¹⁹⁶Hg and which cannot originate from the aforementioned s- and r-processes. Their production is possible in (γ, n), (γ, p), or (γ, α) photonuclear reactions. In view of this, data on photoneutron reactions play an important role in predicting and describing processes leading to the production of p-nuclei. Interest in determining cross sections for photoneutron reactions in the threshold energy region, which is of particular importance for astrophysics, has grown substantially in recent years. The use of modern sources of quasimonoenergetic photons obtained in processes of inverse Compton laser-radiation scattering on relativistic electronsmakes it possible to reveal rather interesting special features of respective cross sections, manifestations of pygmy E1 and M1 resonances, or the production of nuclei in isomeric states, on one hand, and to revisit the problem of systematic discrepancies between data on reaction cross sections from experiments of different types, on the other hand. Data obtained on the basis of our new experimental-theoretical approach to evaluating cross sections for partial photoneutron reactions are invoked in considering these problems.     

Der β-Zerfall des208Tl

An iron-free intermediate-imageβ-ray spectrometer was used to investigate theβ-decay of²⁰⁸T1 in coincidence with the 2.615 MeVγ-ray of²⁰⁸Pb. Fourβ-groups were found, three of which were previously known. The fourth group has an endpoint energy of 0.64±0.03 MeV and an intensity of (4.5±1.5)%. It is supposed that this transition is still complex and feeds a group of levels around the known 4.3 MeV level of²⁰⁸Pb. Noβ-ray of maximum energy 1.032 MeV to the 3.961 MeV level could be found.     

The MTV experiment: searching for T-violation in polarized Li-8 at TRIUMF

The MTV experiment (Mott Polarimetry for T-Violation Experiment) is running at TRIUMF, to search for a large T-violating transverse electron-polarization in polarized ⁸Li β-decay. We aim at reaching precision of 10^?4 for the R-correlation, which is defined as a T-violating triple vector correlation in the β-decay rate function. A Mott polarimeter system using a CDC (Cylindrical Drift Chamber) is used to measure the left-right scattering asymmetry in the Mott scattering from a thin metal foil. In the present study, we aim to discuss systematic effects in Mott polarimetry using the CDC.     

Study of background processes with the formation of neutrons in nuclear reactions in the energy range of 26–32 kev

The nature of background processes accompanying astrophysical nuclear reactions induced by hydrogen, helium, and neon ions in deuterated targets with small cross sections has been studied in calculations and experiments. The experiments have been performed at a Hall pulsed plasma accelerator in the ion energy range of 26–32 keV. The yield of background neutrons and γ-quanta with energies below 4 MeV in the proton-induced D(p, γ)³He reaction is primarily due to the presence of a natural impurity of gaseous deuterium in gaseous hydrogen and the chain of D(D, ³He)n → (n, γ) or (n, n'γ) reactions. A small contribution comes from the chain of D(¹H, ¹H)D → D(D, ³He)n → (n, γ) or (n, n'γ) reactions. It has been shown that background neutrons and γ-quanta from the D(4He, γ)6Li reaction are entirely due to the chain of D(⁴He, ⁴He)D → D(D, ³He)n → (n, γ) or (n, n'γ) reactions. It has been shown that the yield of neutrons and γ-ray photons detected at the interaction of neon ions with deuterated targets is also entirely due to the chain of elastic- scattering reactions of neon ions on deuterons in the target and to subsequent inelastic processes of interaction of deuterons accelerated at elastic scattering with other deuterons of the target. The main contribution to the yields of background neutrons and γ-quanta comes from doubly charged neon ions. The main conclusion is that the explanation of the yield of neutrons and γ-quanta at the interaction of hydrogen, helium, and neon ions with deuterated targets does not require “exotic” theoretical models.     

Data on photoneutron reactions from various experiments for <Superscript>133</Superscript>Cs, <Superscript>138</Superscript>Ba and <Superscript>209</Superscript>Bi nuclei

Basic methods for determining cross sections for photoneutron partial reactions are examined. They are obtained directly in experiments with quasimonoeneregetic annihilation photons or from the cross section for the (γ, xn) = (γ, 1n) + 2(γ, 2n) + 3(γ, 3n) +... neutron-yield reaction in experiments with bremsstrahlung photons by introducing corrections based on statistical nuclear-reaction theory. The difference in the conditions of these experiments, which leads to discrepancies between their results because of sizable systematic errors, is analyzed. Physical criteria are used to study the reliability of data on the photodisintegration of ¹³³Cs, ¹³⁸Ba, and ²⁰⁹Bi nuclei. The cross sections for partial and total reactions satisfying the reliability criteria are evaluated within the experimental–theoretical method (σ^eval(γ, in) = F_i^theor × σ^expt(γ, xn)) on the basis of the experimental cross sections σ^expt(γ, xn) and the results of the calculations within the combined model of photonuclear reactions.     

Zum γ-Spektrum von Po214 (RaC′)

Theγ-ray spectrum arising from Bi²¹⁴→Po²¹⁴ β-decay was investigated by means of a three-crystal-pair-spectrometer. In addition to many already known energies and intensities several new lines have been found, partly improved values for relative intensities are given. These results have been achieved by programming a computer to reproduce the obtained data in a trial and error procedure.