The 18O(18O, 16O)20O reaction at 52 MeV

The structure of the ²⁰O nucleus was studied by the ¹⁸O(¹⁸O, ¹⁶O)²⁰O reaction at E_1ab = 52 MeV. Angular distributions for the transitions to the lowest four states in ²⁰O were obtained and analyzed with finite-range DWBA calculations. Optical potential sets were used which fit the experimental elastic scattering differential cross sections over almost the whole angular range. The two L = 0 transitions to the ground state and the 4.45 MeV state of ²⁰O populated by the ¹⁸O(¹⁸O, ¹⁶O) reaction were analyzed with exact finite-range DWBA calculations using microscopic form factors. These calculations underestimate the absolute cross sections by a factor of 11. The relative strength of the two L = 0 transitions is well reproduced in the ¹⁸O(¹⁸O, ¹⁶O) reaction. However, DWBA calculations for the ¹⁸O(t, p)²⁰O reaction overestimated the relative cross sections for the excited 0⁺ state by a factor of 6. Several model wave functions were tested for the ground-state transition. It was found that the absolute cross sections of the (¹⁸O, ¹⁶O) reaction are very sensitive to the mixing of shell-model configurations. The angular distribution shapes are also slightly dependent on the mixing.     

A microscopic calculation of inelastic electron scattering to the first 2+ state in some even tin isotopes

We present a calculation of the inelastic electron scattering form factors to the first excited 2⁺ state in the even ^{116, 120, 124}Sn isotopes in the plane wave Born approximation. The states of the even tin isotopes are described in terms of one particle parentage coefficients, which have been obtained self-consistently for the pairing-plus-quadrupole model. The experimentally observed structure of the cross section is well reproduced but the magnitude of the cross section shows the need for a DWBA analysis.     

0+ states and E0 and E2 transition rates in even Sn nuclei

0⁺ states and their depopulating E0 and E2 transitions have been studied in ^112–124Sn. Several methods of γ-ray and electron spectrometry have been employed, including special coincidence techniques for lifetime, conversion electron and double Coulomb excitation measurements. For ^114–118Sn the E2 transition probabilities from the first excited 0⁺states (0₂⁺) are about 20 W.u., which is compatible with a vibrational two-phonon character. Also the E0 transition probabilities from these states are within a factor of two from the vibrational values. For the second excited 0⁺ states (0₃⁺) the corresponding E2 and E0 transition probabilities are considerably smaller. A total of 12 E0 transitions have been observed. The 0₃⁺ → 0₂⁺ transition is observed in ^114–120Sn and has in ¹¹⁶Sn a reduced transition probability 1–2 orders of magnitude larger than those of the groundstate E0 transitions, which indicates that the 0₃⁺ and 0₂⁺ states are strong mixtures of components with different 〈r²〉. The 0⁺ states in ¹¹⁶Sn are discussed as possible rotational band heads associated with a deformation β₂ ≈ 0.2. The Coulomb excitation cross section of the 0₂⁺ state is found to be sensitive to an interference term including matrix elements with the 2₂⁺ state. The relative sign of this term has been determined.     

High-spin states in109Sn and their decay to the ground state

An extended level scheme of¹⁰⁹Sn is presented showing high-spin states up to E_x≈ 8 MeV and spins up toJπ=(41/2+). Their decay to the 5/2+ ground state has been observed identifying a 12.8 keV 7/2⁺ → 5/2⁺ transition. A half-life of T_1/2=7(1) ns has been measured for the 17/2⁺ state atE _x =2114 keV. The experimental data are compared with the predictions of shell-model calculations.     

The deformation of the ground and excited states in the Ag and Sn nuclei

The microscopic calculation of the potential energies in the ground and excited states of Ag and Sn nuclei has been performed. The single particle Nilsson potential and the shell correction Strutinski method have been used. The weak sensitivness to nonaxial deformation has been found for even neighbours of these nuclei. The small tendency towards prolate deformation of the ground and excited one-quasiparticle states originating from theg _9/2 proton subshell in^101–105Ag odd isotopes has been noticed. The behaviour with quadrupole e and hexadecapole ε₄ deformation of the ground and two-quasiparticle excited 0⁺ states originating from thed _5/2,g _9/2 andg _7/2 proton subshells andh _11/2 neutron subshell in^112–118Sn has been investigated. The small quadrupole deformation of the excited 0⁺ states has been found what is in agreement with the experimental data concerning the rotational bands build on the first excited 0⁺ states in Sn isotopes.     

Proton direct capture on 40Ca

Excitation functions for the ⁴⁰Ca(p, γ)⁴¹Sc reaction have been measured at 0° and 90° in the proton energy range E_p = 2.1–3.1 MeV. The experimental results have been interpreted in terms of the direct capture process to the first excited state of ⁴¹Sc. The direct capture transition to the ground state has been observed only at a few proton energies. The spectroscopic factor of the first excited state in ⁴¹Sc has been found to be 1.0 ± 0.3. The direct capture cross section to the ground state is consistent with the spectroscopic factor reported from stripping reactions.     

Untersuchung von Kernniveaus des16O bis 14 MeV Anregungsenergie durch unelastische Elektronenstreuung

Using electrons with up to 60 MeV energy, ten transitions in¹⁶O have been studied: twoE0 (6.05 and 12.05 MeV), oneE1 (13.10 MeV), fourE2 (6.92, 9.85, 11.52 and 13.1 MeV), twoM2 (12.53 and 12.96 MeV) and oneE3 (6.13 MeV). The cross sections measured as a function of momentum transfer have been analyzed to yield transition probabilities to the ground state and transition radii. The results are compared with the theory ofBrown andGreen, and with the particle-hole calculations ofLewis andDeForest. For levels at 11.08 and 13.67 MeV, upper limits for the transition probabilities are given.     

Analysis of inelastic scattering of3He on14C at 37.9 MeV

The analogue of the 0⁺ ground state in¹¹⁸Sn has been observed in the compound nucleus¹¹⁸Sb through¹¹⁷Sn(p,nγ)¹¹⁷Sb reaction. The neutron decays of this analogue resonance have been studied from the deexcitingγ-rays of the residual nucleus¹¹⁷Sb. From off resonance excitation functions, spin assignments have been made to states in¹¹⁷Sb, on the basis of Hauser-Feshbach formalism. The resonance parameters of the isobaric analogue resonance have been determined, including the total, proton and neutron decay widths.     

Electron scattering studies of low-lying collective states of even Zn isotopes

The inelastic electron scattering cross sections for the excitation of the low-lying collective states in the even Zn isotopes ⁶⁴Zn, ⁶⁶Zn, ⁶⁸Zn and ⁷⁰Zn have been measured in the momentum transfer region q = 0.3–1.1 fm^?1. Strong transitions to the first 2⁺ and 3^? states have been observed and the modified Tassie model with a two parameter Fermi charge distribution for the ground state was used to extract the values for the reduced transition probability B↑ (Eλ). Besides the investigation of these states, which in the framework of the vibrational model are considered as one-phonon states, special effort was made to measure the transition to the 2⁺ two-phonon states in ⁶⁴Zn (ε = 1.80 MeV) and ⁷⁰Zn (ε = 1.76 MeV). We have applied the anharmonic vibrator model to these two nuclei and have extracted values for the static quadrupole moment of the first excited state.     

Two-proton transfer reaction48Ca(18O,16C)50Ti at 102 MeV

Differential cross sections for¹⁸O elastic scattering and the (¹⁸O,¹⁶C) and (¹⁸O,¹⁷N) reactions on⁴⁸Ca were measured at 102 MeV using a Q3D magnetic spectrograph. The transitions to the 7/2^? ground state (g.s.) of⁴⁹Sc and the 0⁺ (g.s.), 2⁺ (1.554 MeV), 4⁺ (2.675 MeV), and 6⁺ (3.198 MeV) states of⁵⁰Ti were analyzed by DWBA calculations which include finite-range and recoil effects. Simple cluster-transfer calculations were done for all two-proton transfer transitions. For the 0⁺ (g.s.) transition a two-nucleon transfer code employing microscopic wave functions was also used. It was found that absolute cross sections for this kinematically well-matched transition were underrated by a factor of about 7 for a reasonable amount of configuration mixing in the nuclear states involved in this transition. This factor is very close to the value 5 derived for the similarly well-matched⁴⁸Ca(¹⁸O,¹⁶O)⁵⁰Ca reaction.     

Study of the excited states of119Sn by the decay of119g+m In

The decay of^119g+m In to the excited states of¹¹⁹Sn was investigated.¹¹⁹In was produced by the¹²⁰Sn(γ,p)¹¹⁹In reaction on an enriched SnO₂ target. The isomeric transition of 311.25 keV to the¹¹⁹In ground state was observed. In the beta decay of^119m In excited states at 23.9, 920.5, 921.4, 1089.0, 1187.9 and 1249.6keV in¹¹⁹Sn withJ ^π values of 3/2⁺, 3/2⁺, 5/2⁺, 5/2⁺, 3/2⁺ and 1/2⁺ respectively, are fed. In the decay of the¹¹⁹In ground state only the 7/2⁺ level in¹¹⁹Sn at 787.0 keV is fed.     

Zur Gamma- und Röntgenstrahlung von Holmium-164

The photon spectrum in the decay of¹⁶⁴Ho was investigated using a high resolution solid state detector separating theK-X-rays of Dy, Ho and Er. The two γ-rays depopulating the 3⁺ and 2⁺ levels in¹⁶⁴Ho were found to have energies of 56.6 and 37.3 keV. The 91.4 keV radiation of Er from our sample seems to have a non resolved high energy component with about 2.5% intensity. It may be due to the cross-over transition 3⁺→1⁺ or a sum line. The half-life of the isomeric state of¹⁶⁴Ho was found to be 36.7 ± 1 min. The total transition rates between different levels were calculated from the measured photon intensities. The fraction 0.27 found in the branching of thee ^?-capture feeding the 2⁺-state of Dy has nearly the same value as the analog branching in the β^?-decay. Combining the measured complex ground state decay curve and the transition intensities of the isomeric and of the ground state the ground state half-live can be deduced and was found to be (28.1 ± 1.0) min. The corresponding ratio of the ground state and the isomeric state production rates is 2.8₄:1. A ratio of 0.04 was found for the cross section of¹⁶⁵Ho (γ, 3n),¹⁶²Ho and¹⁶⁵Ho (γ,n)¹⁶⁴Ho for a 90 MeV bremsspectrum.     

The binary and ternary fission of thorium,lead and platinum induced by 12.2 GeV protons

We have investigated the decay of^123g+mIn to excited states of¹²³Sn.¹²³In was produced by the¹²⁴Sn(y,p)¹²³In reaction on an enriched SnO₂ target. The isomeric transition to the¹²³In ground state was not observed. In the beta decay of^123m In excited states at 24, 150.9, 920.5, 1194, 2621, 3151, 3256 and 3306 keV in¹²³Sn withJπ values 3/2⁺, 1/2⁺, (5/2⁺), 5/2⁺, 1/2⁺, (1/2⁺, 3/2⁺), 3/2⁺ and (l/2⁺, 3/2⁺), are fed. In the β decay of the¹²¹In ground state only the 7/2⁺ level at 1154 keV in¹²³Sn is observed.     

Spectroscopy of9He with the (13C,13O)-reaction on9Be

First results of the double-charge-exchange reaction⁹Be(¹³C,¹³O)⁹He, E_Lab=380 MeV, are presented. The ground state and an excited state at 3.8 MeV are clearly seen. A preliminary value of the⁹He mass excess is obtained: 41.5±0.6 MeV. Spectra of of the⁹Be(¹³C,¹⁴O) He-reaction have been measured with high resolution. The ground state transition appears as a pronounced sharp peak, but no other narrow peaks are observed.     

Collective excitations in145Ba

High-spin levels in¹²⁵Ba have been produced in the¹¹⁶Sn(¹² C, 3n) reaction and studied by in-beam spectroscopic methods. Two strongly populated band structures are observed. The odd-parity one is based on a 7/2^? state and can be explained as the result of the coupling between anh _11/2 neutron-hole and a prolate type triaxial core. The even-parity band, built on a 7/2⁺ state, corresponds to collective excitations associated with a neutron-hole in theg _7/2 shell. Comparisons with heavier odd-A Ba isotopes and discussions are made in the frame work of the triaxial core model. Nuclear Reactions¹¹⁶Sn(¹²C, 3nγ), E=45–55 MeV; measuredσ(E;E _γ,θ),γγ-coinc,γ-γ delay. Enriched target, Ge(Li) detectors.¹²⁵Ba deduced levels,J,π,γ-mixing.     

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.     

The 16O(6Li,dγ)20Ne reaction

The discrepancy between observed reaction streghts and those predicted from SU(3) considerations in the ¹⁶O(⁶Li, d) reaction has been studied. The effects of both ¹⁶O ground state correlations and of inelastic couplings on the reaction strengths are included. Particle-gamma angular correlations are presented as a test of the reaction predictions. It is found that inclusion of both the ground state correlations and the inelastic coupling does help to resolve the theoretical- experimental discrepancy, and results in generally improved representations of both cross section and angular correlation data.     

16, 18O induced transfer reactions on122, 120Sn

The reactions¹²⁰Sn+72 MeV¹⁸O and¹²²Sn+74 MeV¹⁶O were investigated with time of-flightΔE-E-telescopes. Data are presented for all quasi-elastic reaction channels. The two neutron stripping and pickup reactions (¹⁸O,¹⁶O), (¹⁸O,²⁰O) and (¹⁶O,¹⁸O) are analyzed in detail. It is shown that these heavy ion induced two neutron transfer reactions proceed with essentially the same type of selectivity as the corresponding light ion induced reactions. The differential cross sections for transfer reactions leaving the^{120, 122}Sn nuclei in their 2⁺ first excited states are shown to be influenced by interference effects due to additional inelastic excitations.     

Spectrum of H218O in the 2900 to 3400 cm−1 region

Measurements of line center positions of H₂¹⁸O in the 2900 to 3400 cm^?1 region have been made at high resolution. This region contains absorptions of the (020) band and P-branch absorptions of the (100) and (001) bands of H₂¹⁸O. Values of the energy levels of the (020) state were determined in which ground state energy levels derived by Fraley, Rao, and Jones [J. Mol. Spectrosc.29, 312 (1969)] and Williamson, Rao, and Jones [J. Mol. Spectrosc.40, 372 (1971)] were used in the analysis. A new set of ground state levels was obtained by an iterative procedure.     

Pairing effects in quasi-elastic neutron transfer between Tin isotopes

The transfer of neutrons between low-lying states of Tin isotopes has been measured in the reaction¹²⁰Sn→¹¹²Sn at energies below the Coulomb barrier. The transfer probabilities are deduced as function of the classical minimum distance from transfer and scattering cross sections at different angles and two energies. At the smallest distances very large transfer probabilities,p _t =0.5, are observed for one- and two-neutron transfer. The two-neutron transfer is significantly enhanced as compared to a successive independent single-nucleon transfer. The definition of enhancement is discussed.