Decay of the 4.2-min152Pm into levels of152Sm

After bombardments of enriched¹⁵²Sm with 14-MeV neutrons, three isomers of¹²⁵Pm reaction, have been observed with half-lives of 4.2±0.2 min, 7.5±0.2 min and 15.0±1.0 min. Sources of pure 4.2-min¹⁵²Pm were obtained by separating the promethium from its parent 11-min¹⁵²Nd produced by thermal-neutron induced fission of²³⁵U. The beta and gamma radiations of the 4.2-min¹⁵²Pm have been investigated using semiconductor and scintillation spectrometers. Most of theγ-ray transitions could be placed in a level scheme for 152Sm. Especially interesting is a level at 1083 keV for which the assignmentI ^π=0⁺ is proposed. In a 4πβγ experiment, the ground state feeding of¹⁵²Sm in theβ ^?-decay of the 4.2-min¹⁵²Pm has been measured to be 61% of allβ-ray transitions. AQ _β-value of 3.4±0.2 MeV has been obtained.     

The mean life of the second 0+ state in 42Ca

The mean life of the second excited state in ⁴²Ca (1.84 MeV, O⁺) was measured by a direct electronic timing technique to be 558 ± 8 ps. This result compares with a previous measurement of 480 ± 30 ps which yields a high B(E2) value. The present result gives a B(E2; 0₂⁺ 1.84 MeV → 2₁⁺ 1.52 MeV) value of 484 e² · fm⁴ or 55 single-particle units; the theoretical implications of this are discussed.The accurate mean life was extracted using a convoluted function to describe both the inherent time resolution of the experimental system and the exponential decay of the state of interest.     

Reactions of 40Ar with 159Tb, 142Nd and 144Sm; New α-activities from 189Bi, 173Pt and 177Au

Reactions of ⁴⁰Ar ions with targets of ¹⁵⁹Tb, ¹⁴²Nd, and ¹⁴⁴Sm have been studied at energies below 300 MeV with a helium gas-jet system. Excitation functions for (Ar, xn) reactions, where x = 5–10, were obtained for the radioactive products that decay by α-emission. Based on the characteristics of these excitation functions and on the systematics of α-decay, evidence is presented for the existence of the nuclides ¹⁸⁹Bi with α-particle energy E_α = 6.67±0.01 MeV and half-life < 1.5 sec, and ¹⁷³Pt with E_α = 6.19±0.01 MeV; and for the emission from ¹⁷⁷Au of an α-particle with E_α = 6.15±0.01 MeV.     

Use of the64Ni(36S,34Si)66Zn reaction to measure the mass of34Si

The reaction⁶⁴Ni(³⁶S,³⁴Si)⁶⁶Zn atE=198 MeV has been used to measure the mass excess of³⁴Si; a value of ?19.971 _?0.044 ^+0.037 MeV was obtained. This result which is in agreement with the previous value (?19.85±0.30 MeV) is in excellent agreement with recent shell-model mass predictions. The result is discussed within the context of the proposed region of deformation aroundZ=11,N=20.     

TheK-shell particle parameter of the 122 keV transition in152Sm

TheK-shell particle parameter of the 122 keV transition in¹⁵²Sm has been investigated using different sources and different experimental arrangements. From our measurements we obtain the mean valueb ₂=1.77±0.03. This result deviates from the theoretical value by (6.5±1.5)%. We do not observe hygroscopic effects as reported in Ref.     

A measurement of Γrad/Γ for the 7.654 MeV state of 12C and the rate of the stellar 3α reaction

The branching ratio Γ_rad/Γ for the radiative de-excitation of the 7.654 MeV, 0⁺ state in ¹²C has been measured. Coincidences between α-particles from ¹²C(α, α')¹²C(7.654 MeV) and recoil ¹²C ions at the proper energy and angle were the signature of radiative decay. Conservative techniques were used throughout to avoid the need for large corrections. A value, of Γ_rad/Γ = (3.87±0.25) × 10^?4 was obtained in good agreement with other recent results but substantially higher than the previously accepted value of (2.9±0.3) × 10^?4. Available results are reviewed and a recommended value of Γ_rad/gG is presented. The implication of this result for the rate of the 3α process in stellar helium burning is discussed and a recommended reaction rate is presented.     

Core-breakup reactions of the halo nuclei 11Be and 11Li: momentum distributions and shadow effects

The halo nuclei ¹¹Be and ¹¹Li have been studied in core-breakup reactions where the halo neutrons are expected to be released without a major distortion due to the reaction. The widths of the halo-neutron momentum distributions have been extracted in coincidence with He fragments, Γ = 32 ± 4 MeV/c, and Li fragments, Γ = 42 ± 4 MeV/c for ¹¹Be and with He fragments, Γ = 42 ± 6 MeV/c for ¹¹Li. The ¹¹Be breakup gives a very low neutron multiplicity of 0.38±0.09 which is a manifestation of the shadowing of the neutron in the core-breakup reaction. This value can be understood from a simple theoretical calculation, which also accounts for the observed transverse momentum widths at small angles.     

Mass excess of 147Tb

The mass excess of ¹⁴⁷Tb has been determined from the Q-value measurement of the ¹⁴⁴Sm(^14N, ¹¹Be)¹⁴⁷Tb reaction to be ?71.00 ± 0.05 MeV. The two-proton separation energy provides little evidence for a magic proton shell closure at Z = 64.     

Low-energy πN partial wave analysis

An energy-independent partial-wave analysis has been performed on pion-nucleon elastic and charge-exchange differential cross sections and elastic polarizations, for lab. momenta below 500 MeV/c. The amplitudes were constrained by a simultaneous fixed momentum transfer analysis, which leads to a unique and smooth solution. The masses and widths of Δ⁺⁺ and Δ⁰ have been redetermined from total cross sections as m_Δ⁺⁺ = 1230.9 ± 0.3 MeV, m_Δ⁰ = 1233.6 ± 0.5 MeV, Γ_Δ⁺⁺ = 111 ± 1 MeV and Γ_Δ⁰ = 113 ± 1.5 MeV. For the pion-nucleon coupling constant the value |² = 0.079 ± 0.001 was obtained.     

Messung der Neutronenpolarisation bei der Reaktion12C(d,n 0)13N mit Hilfe der Mott-Schwinger-Streuung

The polarization of neutrons produced in the reaction¹²C(d, n ⁰)¹³N was measured. Deuterons from the Karlsruhe isochronous cyclotron were used to induce this reaction at 51,5 MeV laboratory energy. The degree of polarization was determined by using the special features of Mott-Schwinger scattering. With an uranium scatterer analysing efficiencies of up to 0.92 can be obtained at very small angles (0.23°). The analysing efficiency can be calculated if the differential cross section at 0° and the total cross section is known. These quantities were experimentally determined. The differential cross section for 49.4 MeV neutrons, scattered by uranium, was measured between 0.88° and 2.10°. By an extrapolation the value 43.4±2.6 b/sr was found for the nuclear differential cross section at zero degree. A total cross section ofσ _t=4.80±0.22 b was obtained. The neutron polarization was measured at a reaction angle of 24.5° and the result isP=?0.45±0.07. This value is fairly above the semiclassical 1/3 limit and can be only explained, if spin orbit forces are taken into account. For (d, n) reactions this is the first neutron-polarization measurement above an energy of 20 MeV.     

Radiative width for the 10.35−6.92 MeV transition in 16O

From a measurement of the cross section for ¹²C(α, γ)¹⁶O at the E_α = 4.253±0.014 MeV(E = 10.352±0.011 MeV) resonance, the radiative width for the 10.35 MeV (J^π = 4⁺) to 6.92 MeV (J^π = 2⁺) transition was determined to be Γ_γ = 58±7 meV. This is somewhat higher than the value predicted by large j-j shell-model calculations, but agrees well with predictions based on the rotational and the SU(3) models for a 4p-4h band, and the deformed- basis calculation of Green and Brown.     

The charge radii of198Pt-183Pt

The reactions⁵⁸Ni+¹⁰²Pd→¹⁶⁰W and⁵⁸Ni+¹⁰⁶Cd→¹⁶⁴Os were investigated to search for new decay data of neutron deficient nuclei. Excitation energies of the compound nuclei covered a range from 47 to 89 MeV. Velocity separation of the evaporation residues and position time correlations with the a decays of the implanted nuclei were used. The following new decay data were measured:¹⁶²Os (E_α=(6611 ±30) keV, T_1/2=(1.9±0.7) ms);¹⁵⁸W (T_1/2=(0.9±0.3) ms);¹⁵⁸m_W (E=1.88 MeV, E_α=(8280±30) keV, T_1/2=(0.01-1) ms);^155mLu (E_α=(5575±10) keV); β decay of¹⁵⁶Ta (T_1/2 > 10 ms) to the 8⁺ yrast isomer in¹⁵⁶Hf. A cross section of 5μb was measured for the new isotope¹⁵⁶Ta produced in a p3n evaporation channel from¹⁶⁰W at 64 MeV excitation energy.     

g-factor of the 91.5 keV state in 151Sm

The g-factor of the 91.5 keV state in ¹⁵¹Sm has been measured by the TDPAC method using γγ cascades following the β-decay of 28 h ¹⁵¹Pm. The result is g = ?0.21±0.01. The anisotropy of the angular correlation for the 232.2-25.7 keV cascade is measured to be A = +0.058±0.006. From this an M1/E2 mixing ratio of δ² = 0.008±0.002 for the 232.3 keV transition is concluded. No attenuation of the anisotropy of the angular correlation is observed for aqueous solution sources of SmC1 in excess of hydrochloric acid. Spin and parity assignments for excited states in ¹⁵¹Sm are presented.     

Measurements of the radiative widths of the first T = 1, 2+ state of 20Ne and their relationship to analog β-decays

The radiative widths for decays of the ²⁰Ne T = 1, 2⁺ (10.27 MeV) state were measured by resonance α-capture in the reaction ¹⁶O(α, γ)²⁰Ne. A special windowless gas-cell target yielded a low-background spectrum enabling six γ-branches to be observed with a Ge(Li) detector. The six branches correspond to decays from the 10.27 MeV level to the following levels: 2⁺(7.83 MeV), 2⁺(7.42 MeV), 3^?(5.62 MeV), 2^?(4.97 MeV), 2⁺(1.63 MeV) and 0⁺(g.s.). The branching ratios and radiative widths Γ_γ to these levels are: 7.83 MeV [(0.22 ± 0.06)%, 0.008 ± 0.002 eV], 7.42 MeV [(6.9 ± 0.4)%, 0.31 ± 0.04 eV], 5.62 MeV [(2.1 ± 0.2)%, 0.097 ± 0.014 eV], 4.97 MeV [(1.3 ± 0.1)%, 0.060 ± 0.008 eV], 1.63 MeV [(88.9 ± 0.5)%, 4.08 ± 0.43 eV] and 0.0 MeV [(0.64 ± 0.14)%, 0.029 ± 0.008 eV]. The radiative widths to the 1.63 MeV and 7.42 MeV levels are used to determine the CVC predictions of the weak magnetism form factors and their effects on certain β-decay observables are evaluated.     

Analysis of the K S K S system from the reaction π − p → K S K S n at 40 GeV

On the basis of experimental data from the 6-m spectrometer of the Institute of Theoretical and Experimental Physics (ITEP, Moscow), an amplitude analysis of 40 553 events of the reaction π ^? p → K _S K _S n induced by a negatively charged pion of energy 40 GeV is performed over a broad momentumtransfer range by using a new procedure. The results for |t| > 0.1 GeV² are obtained for the first time. In particular, resonances of mass 1700 and 1900 MeV and width 120 MeV are discovered in the D ₊ wave (there were no such resonances for |t| < 0.1 GeV²). In the region of low momentum transfers, the S wave exhibits a structure that lies in the mass region around 1370 MeV and which requires three resonances for its explanation. Two of these (that of mass 1234 ± 6 MeV and width 47 ± 33 MeV and that of mass 1478 ± 6 MeV and width 119 ± 10 MeV) were found in the studies of A. Etkin et al. [Phys. Rev. D 25, 2446 (1982)] and O.N. Baloshin et al. {Yad. Fiz. 43, 1487 (1986) [Phys. At. Nucl. 43, 959 (1986)]}. The third has a mass of 1389 ± 9 MeV and a width of 30 ± 24 MeV. At high momentum transfers, the S wave is found to feature resonances that have the following parameters: M = 1328 ± 8 MeV and Γ = 237 ± 20 MeV, M = 1440 ± 6 MeV and Γ = 121 ± 15 MeV, and M = 1776 ± 15 MeV and Γ = 250 ± 30 MeV. For the D ₀ wave, it is found that, in addition to the well-known resonances f ₂, a ₂, and f′ ₂, there appear the following resonances in this wave: a resonance of mass 2005 ± 12 MeV and width 209 ± 32 MeV and a resonance of mass 2270 ± 12 MeV and width 90 ± 29 MeV at low |t| and a resonance of mass 1659 ± 6 and width 152 ± 18 and a resonance of mass 2200 ± 13 MeV and width 91 ± 62 MeV at high |t|.     

The (18O, 20Ne) reaction on the even Ni isotopes and the mass of 62Fe

The (¹⁸O, ²⁰Ne) reaction on the even Ni isotopes has been studied at 63.0 MeV with ΔE-E time-of-flight telescopes. From the measured ground-state Q-value for the ⁶⁴Ni(¹⁸O, ²⁰Ne)⁶²Fe reaction, ?1.97±0.20 MeV, a mass excess ?58.87±0.20 MeV is obtained for the ⁶²Fe nucleus. This result is in good agreement with a recent measurement of the β-endpoint energy. Angular distributions for the transitions to the Fe ground states, leaving ²⁰Ne in its ground and 1.63 MeV 2⁺ excited state, yield relative spectroscopic strengths in fair agreement with DWBA calculations based on simple shell-model estimates.     

Observation of a doubly charged charmed baryon in the reaction υp→μ−Σ++c

Evidence for the quasi-elastic production of the doubly charged charmed barron Σ⁺⁺_c has been observed in a vp interaction in BEBC. The mass of the Σ⁺⁺_c and of its decay product, the Λ⁺_c, are 2454±5 MeV and 2288±5 MeV, respectively. The mass difference M(Σ⁺⁺_c)? M(Λ⁺_c) is 166±1 MeV. Combining the Λ⁺_c mass value obtained here with the values obtained in the two Λ⁺_c events previously observed in this experiment, thevalue M(Λ⁺_c)=2283±3 MeV is deduced.     

Evidence for resonant structure near 1780 MeV in e+ e− annihilations observed with the new colliding beam ring at Orsay

We present evidence for the existence of a new J^PC = 1^?? resonance with a mass of 1778 ± 14 (±12) MeV and 150 ± 40 (±30) MeV wide. We tentatively conclude that it is an I = 0 state.     

Messung des Elektroneneinfang am Kern Ga70

The electron capture of Ga⁷⁰ has been observed using a x-ray semiconductor Ge(Li) detector. Measuring the ZnK x-rays and the 0.1755 MeV gamma-rays from the beta decay of Ga⁷⁰ the transition probability to the ground state ofZn⁷⁰ was found to be 0.24%. The log(ft) value is 4.8. The half-life of Ga⁷⁰ has been found to be (21.15±0.06) min and the energies of the gamma-rays are (0.1755±0.0005) MeV and (1.040±0.003) MeV.     

High-resolution (e,e') study of isovector M1 and M2 transitions in the oxygen isotopes: (I). 16O

The M1 and M2 transition strength distribution for ¹⁶O in the excitation energy range from 16 to 20 MeV has been measured in a high-resolution electron scattering experiment. The M1 strength is concentrated in three sharp states at E_x = 16.22, 17.14 and 18.79 MeV (± 0.01 MeV) with B(M1, k)↑ = 0.20 ± 0.02, 0.32 ± 0.03 and 0.13 ± 0.03 μ_N², respectively. An additional strength of 0.35 ± 0.09 μ_N², distributed over eight weakly excited states with excitation energies E_x = 17.4 to 18.0 MeV, brings the total measured M1 strength to B(M1, k)↑ = 1.0 ± 0.1 μ_N². The experimental M2 strength is distributed over states at E_x = 16.82, 17.78, 18.50 and 19.0 MeV (± 0.01 MeV) with B(M2, k)↑ = 19 ± 2, 13 ± 2, 59 ± 7 and 341 ± 51 μ_N² · fm², respectively. Electric transitions were also measured to states at E_x = 16.45 MeV (2⁺, E2), 17.30 MeV (1⁺, E1) and 18.20 MeV (2⁺, E2). Calculations were performed using the modified surface delta interaction in a 2p-2h shell model for the M1 transitions and the random phase approximation for the M2 transitions. The results show the sensitivity of the M1 strength as a measure of ground-state correlations and compare well with results from the ¹⁵N($\text{p}$, γ) reaction.