Three-particle correlations from208Pb+6Li

Three-particle correlations in the reaction²⁰⁸Pb+⁶Li were studied near the Coulomb threshold between \(E_{6_{Li} } = 24\) and 30 MeV. Three reaction mechanisms contribute predominantly to the observed coincidences of the charged particles: 1. Coulomb excitation of the 2.184 MeV,J=3⁺ state of⁶Li, followed by the decay intoα+d, 2. Deuteron pick-up of the⁶Li to the ground state of⁸Be and sequential decay into twoα-particles and 3. Neutron-transfer to the ground state and the first excited states of²⁰⁹Pb:²⁰⁸Pb(⁶Li,αp). The last two reaction mechanisms explain the previously measured large contributions to theα-channel relative to thed-channel.     

Influence of theD and6Li quadrupole moments on theD(α,γ)6Li stellar reaction rate

We have studied theD(α, γ)⁶Li reaction at stellar energies within a potential model. Our calculation improves previous investigations as we explicitely take into account the internal quadrupole moment of the deuteron and ad-state component in the⁶Li ground state. We reproduce the experimental data for energiesE<3 MeV. We find, however, that our improvements represent only minor corrections.     

Microscopic multi-channel calculations for the10Li system

A microscopic multichannel calculation for the¹⁰Li system has been performed in the framework of the Refined Resonating Group Method. Elastic neutron scattering off the⁹Li ground state and transitions into four excited states were considered. The energy spectrum of¹⁰Li is deduced from a phase shift analysis. Besides theJ ^π = 1⁺ ground state, five excited states are identified.     

Die Breite des 4+(11,4 MeV)-Zustandes von8Be aus7Li(d,n) 2α

With the reaction⁷Li+“d→n+⁸Be→n+2α the location and width of the⁸Be(4,+) level is redetermined. While the location at 11.4±0.05 MeV is found in agreement with known values, the width is found to be onlyΓ=2.8±0.2 MeV thereby disagreeing with data fromα-α-scattering but being close to a recent determination from the reaction¹⁰B(d,α)⁸Be (Γ=2.6 MeV). — No indication for participation of an excited state of⁵He in the simultaneously possible reaction via⁵He is found.     

The role of partly Pauli-forbidden states in nucleus-nucleus elastic scattering

The¹²C(⁶Li,d)¹⁶O reaction at 28 MeV and 34 MeV bombarding energy are analized in Zero Range Distorted Wave Born Approximation (ZR-DWBA) utilizing microscopic four-particle transfer form factors. Configuration mixing is taken into account utilizing the Zuker, Buck and McGrory wave functions for¹⁶O. Good agreement is found for the angular distributions. For the relative cross sections to the different excited states, acceptable agreement is found for the 1^? state (7.12 MeV) and 4⁺ (10.56 MeV), while the model clearly underestimates the transition to the 2⁺ state (6.92 MeV).     

Charge exchange reaction 14C(6Li, 6He)14N

Angular distributions of the charge exchange reaction ¹⁴C(⁶Li, ⁶He)¹⁴N leading to the 1⁺ ground state and 3.95 MeV 1⁺, and 5.20 MeV 2^? excited states at the 34 MeV incident beam energy were analyzed and measured. The 62 MeV data of Goodman et al. were also reanalyzed. The direct one-step charge exchange caused by the spin-isospin dependent term in the two-body interaction can account well for the observed data. The strength of spin-isospin dependent effective interaction (gaussian form with a range parameter of 1.8 fm) was extracted to be 18.5 MeV.     

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.     

Experimental investigation of highly excited states of the 5,6He and 5,6Li nuclei in the (6Li, 7Be) and (6Li, 7Li) one-nucleon pickup reactions

The (⁶Li, ⁷Be) and (⁶Li, ⁷Li) reactions on ⁶Li and ⁷Li nuclei were investigated in the angular interval 0°–20° in the laboratory system at a ⁶Li energy of 93 MeV. In addition to low-lying states of the ^5,6He and ^5,6Li nuclei, broad structures were observed near the t(³He)+d and t(³He)+t thresholds at the excitation energies of 16.75 (3/2⁺) and ～20 MeV (for ⁵He), 16.66 (3/2⁺) and ～20 MeV (⁵Li), 14.0 and 25 MeV (⁶He), and ～20 MeV (⁶Li). The angular distributions measured in the ⁷Li(⁶Li, ⁷Be)⁶He reaction for transitions to the ground state (0⁺) and excited states at E _x=1.8 MeV (2⁺) and 14.0 MeV of the ⁶He nucleus were analyzed by the finite-range distorted-wave method assuming the 1p-and 1s-proton pickup mechanism. The (⁶Li, ⁷Be) and (⁶Li, ⁷Li) reactions were shown to proceed predominantly through the one-step pickup mechanism, and the broad structures observed at high excitation energies are considered as quasimolecular states of the t(³He)+d and t(³He)+t types.     

Observation of the nuclear rainbow scattering for12C+12C atE Lab =300 MeV

The elastic and inelastic scattering of¹²C on¹²C has been measured in the angular range between 2.8° and 70.4° in the c.m. system atE _Lab =300 MeV. Optical model calculations have been performed with Woods-Saxon and folded potentials, the ground state and the first 2⁺-state were coupled in the calculations. The large cross sections of the elastic scattering at large angles is related to the nuclear rainbow scattering, which is centered at about 56°. This requires a potential depth of 100 MeV at a distance of 3 fm, the fit to the data is sensitive down to this region. The calculations with the folded potential show a better agreement with the data than those with the Woods-Saxon shape. The total reaction cross section of 1,420 mb, obtained from the optical model analysis, corresponds to the geometrical value; no transparency is observed.     

The decay of121g+m In to levels in121Sn

The decay of¹²¹ g+m In to the excited states of¹²¹Sn was investigated.¹²¹In was produced by the¹²²Sn(γ,p)¹²¹In reaction on an enriched SnO₂ target. Strong indications of the isomeric transition of 321 keV to the¹²¹In ground state were found. In the beta decay of^121m In excited states at 60.1, 908.9, 1101.9, 1120.4, 1403.0, 2864.1, 3119.8 and 3228 keV in¹²¹Sn withJ ^π values 1/2⁺, 3/2(5/2)⁺, 3/2⁺, 5/2⁺, 5/2⁺ and 1/2⁺ or 3/2⁺ for the three levels around 3 MeV, are fed. In the decay of the¹²¹In ground state only the 7/2⁺ level in¹²¹Sn at 925.3 keV is fed.     

The 28Si(7Li, 7Be)28Al reaction at 36 MeV

The ²⁸Si(⁷Li, ⁷Be)²⁸Al reaction has been investigated at E_7Li = 36 MeV. States and groups of states were observed up to 5.3 MeV excitation in the ²⁸Al+⁷Be system. Experimental angular distribution for unresolved doublets of states at ≈ 0.0 and 0.44 MeV excitation, corresponding to ⁷Be in its ground state (⁷Be₀) and first excited states (⁷Be₁) with ²⁸Al in its ground state (3⁺) and first excited state (0.031 MeV, 2⁺) are compared with microscopic distorted wave approximation calculations.     

Excited states of154Nd studied through the decay of154Pr

Excited states in the neutron-rich doubly-odd nucleus⁷⁸As have been identified for the first time by proton-γ and γ-γ coincidence measurements via the⁷⁶Ge(α, pn) reaction at 32, 36, and 40 MeV beam energy. Four levels have been found to decay with lifetimes in the nanosecond region. The 5⁽⁺⁾ to (10⁺) states are ascribed to the (πg _9/2?νg _9/2) intruder two-quasiparticle configuration with some collective components in the 9⁽⁺⁾ and (10⁺) states.     

High spin states in97Rh

High spin states in⁹⁷Rh were excited via the⁹⁶Ru (α,2np) reaction at 45 MeV. As a main finding we have observed a positive parity band, built on the 9/2⁺ ground state, which depopulated levels at 3,550.7 (25/2⁺), 3,259.1 (23/2⁺), 2,895.1 (23/2⁺), 1,961.3 (19/2⁺), 1,553.1 (17/2⁺) and 857.1 (13/2⁺). Also we have excited levels at 3,055.8 (21/2), 2,225.4 (17/2) and 1,463.5 (15/2), which most likely are negative parity states.     

Study of short-lived silver isotopes with a laser ion source

The continuum part of the⁶Li (a,a)⁶Li (1.47–2.47 MeV) scattering data at E_a=50 MeV are extracted in two discretized bins. Coupled-channel calculations are carried out coupling the 1⁺ ground state of⁶Li with both the resonant, 3⁺ ₁ state, and two non-resonant continuum states. The discretized continuum of the⁶Li (p,p)⁶Li (1.75–3.25 MeV) scattering data at E_p=65 MeV are also analysed on the same footing. In both the cases the effect of coupling is found to be minimal.     

FastM1 transitions in85Rb

Excited states in⁸⁵Rb have been studied via the⁸²Se(⁷Li, 4n) reaction by using in-beamγ-ray spectroscopy. On the basis of new experimental data on coincidence relations, angular distributions and linear polarizations of theγ-rays the yrast sequence has been extended up to a 33/2⁺ level at 7.1 MeV excitation energy. Using the DSA method mean lifetimes have been determined for 9 levels. Above the 21/2⁺ yrast state 5 fast M1 transitions withB (M 1) ≧0.3 W.u. have been identified. They are interpreted as transitions between recoupled states of the configuration πg_9/2ν(g_9/2) ₈₊ ^?2 or πg_9/2(f ₅ ² /?1p ₃ ^2?1 )₄₊ν(g_9/2) ₈₊ ^?2 .     

Shell model and octupole states in148Gd from in-beam experiments

Through (α, 4n) and (τ, 3n) reactions the high-spin states in the two-neutron nucleus¹⁴⁸Gd were populated up toI ^π=21? at 7.2 MeV, including numerous states above the yrast line. The¹⁴⁸Gd energy spectrum is interpreted in terms of the spherical shell model. Identification of the (νf _7/2 i _{1 3/2})_10? state gives the νi _13/2 single particle energy free of octupole admixtures as 2.1(1) MeV. Eight high-spin states between 1.2 and 3.7 MeV were identified as the couplings of the two valence-particles to the¹⁴⁶Gd octupole phonon, and three above-lying levels are assigned as double-octupole excitations including a 12⁺ state which decays by anE3-E3 stretched cascade. All these octupole levels can be quantitatively predicted from the one-particle x phonon spectrum of¹⁴⁷Gd. The high-spin states above 3 MeV are four-quasiparticle excitations ofπ ⁺¹ π ^?1 ν ² andπ ² ν ² type and their energies are in good accord with shell model estimates.     

Spatial periphery of lithium and beryllium isotopes

The spatial structure of the periphery of lithium and beryllium isotopes is studied by means of charge-exchange reactions and the (t, p) and (d, p) reactions on their nuclei. It is shown that the 0⁺ isobaric-analog state of ⁶Li at 3.56 MeV has a halo structure formed by a proton and a neutron, that there is virtually no manifestation of a neutron halo in the ground state of the ⁹Li nucleus, and that the ¹¹Li nucleus has a Borromean halo structure that two neutrons form with respect to the ⁹Li core and which manifests itself in cigar and dineutron configurations. The ¹⁰Be nucleus has a substantial two-neutron periphery in either configuration both in the ground and in the 2⁺ excited state at 3.37MeV.     

New search for 0νEC/EC and 2νEC/EC decay of 106Cd

The studies aimed at decreasing the background of the TGV-2 spectrometer have led to constructive changes in the cryostat and increased the sensitivity of the 32-detector spectrometer. New search for 0νEC/EC, 2νEC/EC) decays of ¹⁰⁶Cd was started with ～13.6 g of ¹⁰⁶Cd with enrichment of 75%. The evaluation of the experimental data accumulated for 4800 h was performed. Limits (at 90% CL) on the half-lives of 0νEC/EC resonant decay of ¹⁰⁶Cd to the 2741 keV excited state of ¹⁰⁶Pd (T _1/2 ≥ 6.5 × 10¹⁹ y) and on t 2νEC/EC decay to the ground state of ¹⁰⁶Pd (0⁺ → 0⁺, g.s.) (T _1/2 ≥ 1.7 × 10²⁰ y) were obtained. The limits on the other branches of ¹⁰⁶Cd decay—2νEC/EC decay to the 2⁺, 512 keV and 0 ₁ ⁺ , 1334 keV excited states of ¹⁰⁶Pd and 2νβ⁺β⁺ and 2νβ⁺ EC decays of ¹⁰⁶Cd to the ground and excited states of ¹⁰⁶Pd were improved.     

Spins and parities of hole states in25Na and25Mg

Angular distributions of differential cross sections and vector analyzing powers were measured forl=0, 1 and 2 transitions induced by the \(^{26} Mg\left( {\overrightarrow d ,\tau } \right)^{25} Na\) reaction at 52 MeV. The following spins and parities of final states in²⁵Na were deduced:J ^π =1/2⁺ (1.069 MeV), 3/2⁺ (2.202 MeV), 5/2⁺ (2.914 MeV), 1/2^? (3.995 MeV) and 3/2^? (5.190, 5.690, 6.549 and 7.603 MeV). The DWBA analysis of proton and neutron pick-up spectra obtained from a parallel measurement of the²⁶Mg(d, τ)²⁵Na and²⁶Mg(d, t)²⁵Mg reactions allows the identification ofT=3/2 analog states in²⁵Mg. Interpretation in terms of the Nilsson model of energies and spectroscopic factors of the first 1/2^? and 3/2^? hole states observed in proton pick-up reactions from even 1d _5/2- shell nuclei indicates a close correspondence of the final state deformations with those of the first excited 2⁺ states in the target nuclei.     

Elastic and inelastic scattering of protons from Li between 25 and 45 MeV

The elastic and inelastic scattering of protons from ⁶Li has been studied at incident energies of 25.9, 29.9, 35.0, 40.1 and 45.4 MeV. The 2.18 MeV (3⁺, T = 0) first excited state of ⁶Li was found to be strongly excited, but the 3.56 MeV (0⁺, T = 1) second excited state was quite weakly excited. Angular distributions for excitation of the 2.18 MeV level were measured at all five energies, while angular distributions for excitation of the 3.56 MeV level were extracted only at 25.9 and 45.4 MeV. To test the applicability of the optical model for the scattering of protons from such a light nucleus the elastic scattering angular distributions have been analyzed using the eleven-parameter search code SEEK. Available polarization angular distributions were included in the analysis. Reasonable fits to the data have been obtained with an average geometry potential. Theoretical estimates of the real part of the optical potential and the inelastic scattering differential cross sections have been made using the microscopic model for proton-nucleus scattering. Both phenomenological and realistic forces have been considered and the necessary nuclear transition densities have been extracted from experimental elastic and inelastic electron scattering data. An estimate of a possible spin-spin term in the optical potential has also been made.