<Superscript>18</Superscript>Ne diproton decay

Two proton radioactivity studies have been performed on excited states of ¹⁸Ne produced, among other fragments, by ²⁰Ne projectile fragmentation and excited via Coulomb excitation on a Pb target. Every incoming ion was tagged before interacting with the lead target on an event by event basis in order to discriminate the secondary reactions according to the projectile. Decay of ¹⁸Ne levels has been studied by complete kinematical reconstruction. In spite of the low statistics a couple of events looks very promising for two proton correlated emission.     

Structure of low-lying quadrupole states in nucleus <Superscript>134</Superscript>Xe

Starting from the Skyrme interaction, we study the M1 transitions between vibration quadrupole states. The finite rank separable approach for quasiparticle random phase approximation is used. As an example, we investigate the properties of the low-energy spectrum of quadrupole excitations in nucleus ¹³⁴Xe.     

Alpha-cluster states in <Superscript>18</Superscript>O

The excitation function of elastic α-particle scattering on ¹⁴C has been measured in the laboratory energy range 16.3–19.2 MeV using a backscattering technique with a thick target. These data were analyzed together with the old low-energy data of G.L. Morgan et al. in the framework of the R-matrix formalism. Spin-parity assignments were made for 32 states in ¹⁸O in the excitation range 9–20 MeV. The estimates of the widths of the states are also presented. The 0⁺ and 0^?α-cluster bands appeared to be well separated by 5.6 MeV (as in ¹⁶O and ²⁰Ne). We have not found a confirmation of existence of the negative-parity molecular states proposed by M. Gai et al. We observed an effect of a doubling of α-cluster levels in ¹⁸O similar to that found in ²²Ne.     

Concerning positive-parity collective states in <Superscript>18</Superscript>O

I discuss collective positive-parity states in ¹⁸O in light of two recent experiments. Single-particle widths have been calculated and used to extract spectroscopic factors. Special attention is given to 4p -2h and 6p -4h cluster bands.     

Structure of low-lying <Superscript>12</Superscript>C resonances

The hyperspherical adiabatic expansion is combined with complex scaling and used to calculate low-lying nuclear resonances of ¹²C in the 3α model. We use Ali-Bodmer potentials and compare results for other potentials α-α with similar ⁸Be properties. A three-body potential is used to adjust the ¹²C resonance positions to desired values extending the applicability of the method to many-body systems decaying into three α-particles. For natural choices of three-body potentials we find 14 resonances below the proton separation threshold, i.e. two 0⁺, three 2⁺, two 4⁺, one of each of 1^±, 2^-, 3^±, 4^-, and 6⁺. The partial-wave decomposition of each resonance is calculated as a function of the hyperradius. Strong variation is found from small to large distance. The connection to previous experimental and theoretical results is discussed and agreements as well as disagreements are emphasized.     

Spin-orbit coupling in the ground and low-lying excited states of HF<Superscript>+</Superscript> and HF<Superscript>-</Superscript>

Electronic structure and spectroscopic properties B _e, ω_e, ω_e x _e, α_e, T _e of ground state and the low-lying excited states of HF⁺ and HF^- molecular ions were investigated within scalar relativistic multireference configuration interaction with single and double excitations framework using the GAMESS-US program package. All potential energy curves (PECs) were calculated using the relativistic complete active space self-consistent field/spin-orbit multi-configuration quasi-degenerate perturbation theory (CASSCF/SO-MCQDPT). The curves are all fitted to the analytical potential energy function (APEF), from which accurate spectroscopic constants are derived. The spin-orbit splitting was also been studied, the split value of X²P^{2}{\rm \Pi} state of HF⁺ is determined to be 288.38 cm^-1. The calculated properties are in good agreement with the available experimental value. Spectroscopic constants of the ground states of HF^- that have never been observed in experiment are obtained. These curves provide an interpretation of the known experimental observations on this system and suggest a number of further experiments which possible provide a critical test of this data.     

1<Superscript>+</Superscript>(0<Superscript>+</Superscript>) state at 12.4 MeV in <Superscript>20</Superscript>Ne

Careful review of all the evidence makes it clear that at least three states are important at 12.4-MeV excitation in ²⁰Ne (four, if the broad (2⁺) at 12.5 MeV is included). The three states are 3 ^- , 0 ⁺ , and 1 ⁺ (0⁺). The latter, which is quite strong in ¹⁹F (³He, d) singles, is probably the state observed in coincidence with 6.13-MeV γ-rays in ¹⁹F(³He, dγ). Received: 19 August 2002 / Accepted: 28 October 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: fortune@physics.upenn.edu Communicated by D. Guerreau     

Light-charged-particle emission from hot <Superscript>32</Superscript>S<Superscript>*</Superscript>formed in <Superscript>20</Superscript>Ne + <Superscript>12</Superscript>C reaction

Inclusive energy distributions for light charged particles (p , d , t and have been measured in the ²⁰Ne (158, 170, 180, 200 MeV) + ¹²C reactionsintheangularrange$10^°$ - - $50^°$.Exclusivelight-charged-particleenergydistributionmeasurementswerealsodoneforthesamesystemat158 MeVbombardingenergybyin - planelightchargedparticle - - fragmentcoincidence.Pre - equilibriumcomponentshavebeenseparatedoutfromprotonenergyspectrausingthemovingsourcemodelconsideringtwosources.ThedatahavebeencomparedwiththepredictionsofthestatisticalmodelcodeCASCADE.Ithasbeenobservedthatsignificantdeformationeffectswereneededtobeintroducedinthecompoundnucleusinordertoexplaintheshapeoftheevaporated$d$,$t$energyspectra.Forprotons, evaporatedenergyspectrawereratherinsensitivetonucleardeformation, thoughangulardistributionscouldnotbeexplainedwithoutdeformation.Thedecaysequenceofthehot$³²S$nucleushasbeeninvestigatedthroughexclusivelight - - charged - particlemeasurementsusingthe$²⁰Ne$$(158 MeV) + $¹²C reaction. Information on the sequential decay chain has been extracted through a comparison of the experimental data with the predictions of the statistical model. It is observed from the present analysis that exclusive light-charged-particle data may be used as a powerful tool to probe the decay sequence of hot light compound systems.     

Contribution of quasiparticle-phonon,recoil and coriolis interactions in describing low-lying states of <Superscript>133</Superscript>Nd isotope

A quasiparticle-phonon coupling based on one quadrupole phonon is developed. The coupling is constructed by using a deformed average field of Nilsson, a monopole pairing interaction and a quadrupole-quadrupole force. Microscopic structure of the quadrupole phonon is given from the Tamm-Dancoff Approximation. The two effects of recoil and Coriolis forces are included with the assumption of a symmetric rotational motion. Since theoretical treatment is performed for an odd- A nuclei the configuration of intrinsic states should contain both one-quasiparticle and quasiparticle-phonon components. This method is applied to describe the level scheme of ¹³³Nd for which an agreement with experimental data is obtained. The results are also found similar to previous calculations obtained by the Particle plus Triaxial Rotor Model. Received: 23 August 1999     

Double-beta decay of <Superscript>100</Superscript>Mo to 0<Superscript>+</Superscript> excited states in <Superscript>100</Superscript>Ru

A brief review on the 2νββ decay of ¹⁰⁰Mo to the 0⁺ excited state in ¹⁰⁰Ru is performed. A weighted-average half-life value for the decay has been obtained, T_1/2 = (6.8 ± 1.2) × 10²⁰ yr. The corresponding average value for the nuclear matrix element was extracted, 0.095 ± 0.009.     

Lifetimes of <Superscript>48</Superscript>Ti, <Superscript>52</Superscript>Cr and <Superscript>80</Superscript>Se excited states

Doppler shift attenuation was used to measure the lifetimes of ⁴⁸Ti, ⁵²Cr and ⁸⁰Se nuclei excited states populated in the (n, n′γ) reaction using the neutron beam of the Republic of Kazakhstan’s WWR-K research reactor. The measured data are in good agreement with the latest literature data.     

Structure of 2<Subscript>1,2</Subscript> <Superscript>+</Superscript> states in <Superscript>132,134,136</Superscript>Te

Starting fromthe Skyrme interaction f_ together with the volume pairing interaction, we study the g factors for the 2_1,2⁺ excitations of ^132,134,136Te. The coupling between one- and two-phonon terms in the wave functions of excited states is taken into account within the finite-rank separable approximation. Using the same set of parameters we describe the available experimental data and give the prediction for ¹³⁶Te, g(2₁⁺) = ?0.18 in comparison to +0.32 in the case of ¹³²Te.     

Low-spin states in <Superscript>182</Superscript>Os and K<Superscript>π</Superscript> = 0<Superscript>+</Superscript>, 2<Superscript>+</Superscript> excited bands

Excited states in ¹⁸²Os were populated by the β⁺/EC decay of ¹⁸²Ir following mass separation. Gamma-ray and conversion electron spectroscopy techniques were employed. Monopole (E0) contributions were determined in transitions populating the ground-state band. A systematic study of the low-spin structures in the Os isotopes is presented and a detailed analysis in the framework of a microscopic configuration mixing approach is performed.     

The low-lying rotational bands of the neutron-rich nucleus <Superscript>172</Superscript>Tm

The microscopic mechanism of four experimentally observed bands in 172Tm is investigated using the particle-number conserving method of the cranked shell model with monopole and quadrupole paring interactions.The experimental results,including the moments of inertia and angular momentum alignments of four bands in 172Tm are reproduced well by the particle-number conserving calculations.The ω variation of the occupation probability of each cranked orbital and the contribution to moment of inertia from each c...     

Interaction of intermediate-energy protons with <Superscript>20</Superscript>Ne and <Superscript>24</Superscript>Mg nuclei within the multiple-scattering model

Observables of the elastic and inelastic scattering of 800- and 250-MeV protons on ²⁰Ne and ²⁴Mg nuclei were calculated on the basis of the theory of multiple diffractive scattering and the dispersive α-cluster model. The ²⁰Ne and ²⁴Mg nuclei were assumed to consist of a core (¹⁶O nucleus) and additional alpha-particle clusters, which could be situated with the highest probability both in the vicinity of the center of mass of the core and outside the core. The multiparticle densities of these nuclei and single-particle nucleon-distribution densities as obtained from the dispersive α-cluster model were used in the calculations. The differential cross sections and polarizations for elastic and inelastic p ²⁰Ne and p ²⁴Mg scattering at the energy of 800 MeV are in better agreement with experimental data than the analogous calculations at the energy of 250 MeV. The spin-rotation functions calculated in the singleparticle approximation for elastic p ²⁰Ne and p ²⁴Mg scattering at these two energy values differ qualitatively from their counterparts calculated on the basis of the dispersive α-cluster model.     

Elastic and inelastic scattering of 800-MeV protons on <Superscript>16</Superscript>O and <Superscript>20</Superscript>Ne nuclei

Differential cross sections and polarization observables for the elastic and inelastic scattering of 800-MeV protons on ¹⁶O and ²⁰Ne nuclei are calculated on the basis of the theory of multiple diffractive scattering and the α-cluster model involving dispersion. The single-particle nucleon-density distributions obtained within the α-cluster model involving dispersion are used in the calculations. The differential cross sections and polarization calculated for elastic and inelastic p¹⁶O and p²⁰Ne scattering are compatible with available experimental data. The spin-rotation functions calculated for elastic p¹⁶O and p²⁰Ne scattering within the independent-nucleon model differ qualitatively from their counterparts calculated within the α-cluster model involving dispersion.