Proton-hole states in 115In observed in the 116Sn(d, 3He) reaction

The ¹¹⁶Sn(d, ³He)¹¹⁵In reaction has been investigated at E_d = 50 MeV. Thirteen transitions to states up to 3 MeV excitation energy were studied. The measured angular distributions were compared with DWBA calculations and transferred angular momenta and spectroscopic factors were deduced. Levels at 1.04, 2.23 and 2.52 MeV were found to be excited most likely by l = 3 angular momentum transfer in contrast to previous investigations at lower incident energies in which no l = 3 transitions have been observed.     

Measurement of the total neutron cross section of 14N and 24Mg

The total neutron cross section of ¹⁴N and ²⁴Mg has been determined for neutron energies between 1.0 and 5.2 MeV. For this purpose, the attenuation of a continuous neutron spectrum in absorbing samples of liquid natural nitrogen and enriched ²⁴Mg has been measured in open geometry with the time-of-flight technique. A time resolution of 0.07 ns/m was achieved. The obtained data improve the knowledge on the cross section of ¹⁴N above 2 MeV and of ²⁴Mg in the total energy range. In the latter, a large number of resonances is observed for the first time.     

Energy levels of 92Nb and 94Tc from 92Zr, 94Mo(p,nγ)92Nb, 94Tc

The γ-decays of the energy levels of ⁹²Nb and ⁹⁴Tc were measured following the ⁹²Zr(p, n)⁹²Nb and ⁹⁴Mo(p, n)⁹⁴Tc reactions. For ⁹²Nb the γ-ray thresholds were measured and a detailed excitation function was obtained near the ⁹³Zr ground-state isobaric analog resonance. Also, γ-γ coincidence measurements with two Ge(Li) detectors were made for both ⁹²Nb and ⁹⁴Tc. The coincidence measurements determined ten energy levels in ⁹²Nb and two levels in ⁹⁴Tc. A comparison with particle transfer reactions is used to elucidate the structure of ⁹²Nb levels observed here but not seen in the transfer reactions.     

9Be + 12C, 9Be + 16O,9Be + 19F reactions at energies below the barrier

The ¹⁶O + ⁹Be reactions have been studied from E_c.m. = 2.0 MeV to 5.1 MeV, an energy near the top of the Coulomb barrier. The cross section for the neutron transfer reaction ⁹Be(¹⁶O,¹⁷O¹ (0.87 MeV))⁸Be has been measured over this range by detecting the prompt 0.87 MeV γ-rays. The total fusion cross section has been determined from E_c.m. = 2.8 to 5.1 MeV by observing individual γ-ray transitions in the evaporation residues with a Ge(Li) detector, and then summing the separate yields. Direct processes are found to dominate the reaction yield below E_c.m. = 4 MeV. A comparison of the energy dependence of the fusion cross section for this reaction and the ¹²C + ¹³C reaction, which proceeds via the formation of the same compound nucleus, ²⁵Mg, reveals differences at sub-barrier energies. Optical model and incoming-wave boundary condition calculations are presented. Data have also been obtained for the near optimum Q-value neutron-transfer reactions ⁹Be(¹²C, ¹³C¹)⁸Be and ⁹Be(¹⁹F, ²⁰F)⁸Be, and these are discussed in terms of a simple model of sub-barrier direct reactions.     

Non-linear density dependence of the Δ-self-energy in nuclear matter and its implications in pionic atoms

The $\text{Δ(}\text{3}\text{2}\text{,}\text{3}\text{2}$) self-energy in a nuclear medium is shown to be highly non-linear in density, when proper care is taken of the virtual meson propagation in the medium and retardation effects. As a consequence the p-wave absorptive potential for pionic atoms diverges appreciably from the standard ρ² form. A fit to the existing data on pionic atoms is carried out with the new functional of the density and turns out to be as good as those with the ρ² functional. The successful fits with such different density functionals are due to a very narrow range of nuclear effective densities felt by the pion in the observed pionic atoms. The influence of these effects in related problems is discussed along with the suggestion to widen the range of nuclear densities felt by the pions by looking at other nuclear phenomena.     

Quasi-fission and other strongly damped collisions between 63Cu ions and 197Au nuclei

The interaction of ⁶³Cu ions with ¹⁹⁷Au nuclei have been studied experimentally at incident energies of 365 and 443 MeV (1.1 and 1.4 times the Coulomb barrier). Mass and kinetic energy distributions of reaction products have been measured at several angles. Near the grazing angle, a continuous transition was found from elastic events to partially damped (PD) events, and to fully damped events (quasi-fission, QF). Away from the grazing angle a clean separation between elastic and QF events was observed. Events that may be due to fission following fusion (CF) were also obtained. Results are discussed in terms of decomposition into PD, QF, and CF components. The QF kinetic energy is independent of the incident energy (implying full damping of the initial relative motion). It is lower than the Coulomb barrier and close to the kinetic energies from the fission of similar systems. The angular distribution is peaked somewhat forward of the grazing angle for low mass transfers. For large mass transfers the yield increases slowly with decreasing angle. At 443 MeV a large contribution from negative angles is present. σ_QF accounts for more than 65 % of the reaction cross section σ_R at 443 MeV and for more than 50 % at 365 MeV. The upper limit on CF is about 10 % of σ_R, and σ_PDis of the order of 25 % of σ_R.     

Large transient magnetic fields for rare-earth ions recoiling in gadolinium and g-factors of high-spin states in 156, 158, 160Gd

We have determined the transient magnetic field for Coulomb-excited rare-earth nuclei recoiling with velocities in the range between 0.7ν₀ and 6ν₀ into ferromagnetic gadolinium cooled to a temperature T = 80 K. Measured and calculated g-factors in ¹⁶⁹Tm have been used as calibration standards. The transient field is found at first to increase with increasing recoil velocity, and then to level off, approaching a nearly constant value of 5.5 kT at ν = 6ν₀. At the higher velocities (3ν₀ < ν < 6ν₀) the transient fields for ¹⁶⁹Tm recoils in gadolinium are a factor of 1.42 ± 0.12 larger than those in iron, whereas the densities of polarized electrons are the same in both ferromagnets. This result demonstrates that an explanation of the transient field must take into account the atomic structure of the host (and probably also that of the recoil). The transient field is too large to be described only in a statistical picture in which inner-shell (ns) vancancies are filled by capture of polarized (4f) electrons. Possible mechanisms may involve either polarization transfer from the outer shells by spin-flip interactions, or direct vacancy polarization by diabatic molecular orbitals.The transient field calibration has been corroborated making use of known g-factors of low-spin states in ^{156, 158, 160}Gd populated by Coulomb excitation of thick Gd single crystals. For the high-spin states in these nuclei, the g-factors are found to decrease slightly, with the ratio $\text{g(10}{}^{\mathrm{+}}\text{)}\text{g(2}{}^{\mathrm{+}}$) reduced to 0.89±0.12, 0.83±0.11, and 0.93±0.13, respectively. Similar decreases have been observed previously for other N = 90?96 nuclei.     

Static quadrupole moments of the first excited states of 200Hg and 202Hg

The static quadrupole moments Q_2⁺ and B(E2; 0⁺ → 2⁺) values of the 2⁺ first excited states of ²⁰⁰Hg and ²⁰²Hg have been determined using the reorientation effect in Coulomb excitation. An annular silicon surface-barrier detector was used to detect backscattered ⁴He, ¹²C and ¹⁶O projectiles. It is found that for ²⁰⁰Hg, Q_2⁺ = +1.07 ± 0.19 e · b(+0.98 ± 0.19 e · b) for destructive (constructive) interference from the 2^+′ state, and B(E2; 0⁺ → 2⁺) = 0.853 ± 0.007 e² · b². For ²⁰²Hg, we find Q_2⁺ = +1.01 ± 0.13 e · b (+0.87 ± 0.13 e · b) and B(E2; 0⁺ → 2⁺) = 0.605 ± 0.005 e² · b². The Q_2⁺ value obtained for ²⁰⁰Hg is in agreement with previous work, but that for ²⁰²Hg is not. The results obtained are compared with the predictions of various nuclear models, and the mass dependence of Q_2⁺ in the region 182 ≦ A ≦ 206 is examined.