States In 209Pb Research Articles

The continuum shell-model neutron states of209Pb

The neutron strength distributions of the three high-spin 1k 17/2, 2h 11/2 and 1j13/2 states of209Pb have been obtained within the formalism of the core-polarisation effect where the effect of interaction of the neutron shell-model states of209Pb with the collective vibrational states (originating also from the giant resonances) have been taken into consideration. The theoretical results have been discussed in the light of works on 1k 17/2, 2h111/2 and 1j13/2 neutron orbitals of209Pb. The shell-model energies of the neutron states have been obtained by Skyrme-Hartree-Fock method

γ Spectroscopy of 209Pb with deep inelastic reactions

High spin states in nuclei around 208Pb were populated in deep inelastic collisions of 76Ge, 136Xe, and 208Pb projectiles with 208Pb targets at beam energies about 12% above the Coulomb barrier. New states in 209Pb were found by measuring γ-γ-coincidences. They are interpreted as the yrast states that originate from the coupling of one neutron to the lowest excitations of the 208Pb core. The results are discussed in the frame of the shell model.

Particle decay of high-lying states in odd nuclei

A method for calculating non-statistical particle decay of excited states in odd nuclei is presented. Using the quasiparticle-phonon model partial cross sections and branching ratios for the neutron decay of the high angular momentum states in 209 Pb and 91 Zr excited by means of the (α, 3 He) reaction have been evaluated. The calculated branching ratios are compared with existing experimental data.

On the direct nucleon decay of high-spin subbarrier single-particle states in near-magic nuclei

Abstract The description of the direct nucleon decay of high-spin subbarrier one-particle states in near-magic nuclei is attempted using a simple optical model and the simplest version of the coupled-channel approach. The branching ratios for the direct decay of the several single-neutron states in 209Pb and 91Zr to the ground state and to the low-lying collective states of 208Pb and 90Zr, respectively, are evaluated. Results are compared with recent experimental data.

Non-statistical neutron decay of high-lying states in odd nuclei

Abstract We present a method for calculating non-statistical particle decay of excited states in odd nuclei. Using the quasiparticle-phonon model we evaluate the escape widths of high-lying states in 209Pb. It is found for high angular momentum states ( 11 2 − , 13 2 − , 17 2 + ) direct escape widths are in the range 10–100 keV at the peaks of the strength functions.

Fragmentation of the high spin discrete neutron and proton states of209Pb and209Bi

The distribution of the discrete 1h 9/2, 2f 7/2, 1i 13/2 and 2f 5/2 proton states of209Bi and 2g 9/2, 1i 11/2, 1j 15/2 and 2g7/2 neutron states of209Pb have been obtained within the particle-vibration coupling model calculation and compared with the experimental datas baising on the most recent high resolution stripping reaction on208Pb using 480 MeV12C projectile. The optimised shell model energies arising from the core-polarisation effect have profound influence for both the study of the structures of the high spin continuum shell model states of208Pb and stability of superheavy nuclei.

Evidence of projectile polarisation effects on the reaction 208Pb( 17O, 16O) 209Pb

Abstract Coupled reaction channels calculations (CRC) of the reactions 208 Pb( 17 O, 16 O) 209 Pb leading to different states of 209 Pb are compared with DWBA predictions at projectile energies of 78, 86 and 102 MeV. The calculations exhibit strong effects of multistep processes on Q -value and angular-momentum-mismatched transfer reactions. It is shown that the contribution to the transfer through the inelastic excitation of 17 O contains a major part of the multistep effect. A simple three-channel model comprising the elastic, inelastic and transfer channels is constructed which simulates the CRC effects on the transfer cross sections. The polarization effects of the eliminated channels give rise to effective potentials which are mainly imaginary.

High-spin shell-model states in 209Pb

Three unbound high-spin shell-model states in 209Pb (1k172, 1j132 and 2h112) are fou have measurable strengths at about 3.5 to 5.6 MeV excitation as a result of the coupling of these neutron states with the collective vibrational states of 208Pb. All the four 1j152 states and four 2h112 states observed in a recent 208Pb(d, p) reaction study are accounted for by this model. Two more states at 3.93 and 4.12 MeV, seen in 208Pb(α, 3He) reactions, may correspond to the fragmented 1k172 state.

Pion photoproduction to single-particle states in209Pb

Pion photoproduction to single-particle states in209Pb

Gamma decay of particle-core states in 209Pb

Abstract A γ-decay scheme for levels in 209Pb up to 4.13 MeV of excitation has been established by means of the reaction 208Pb(d, pγ)209Pb. In high efficiency p-γ coincidence measurements γ-cascades have been observed from the single-particle states and from core-excited states with very small single-particle strength. Assuming a qualitative validity of the weak-coupling model spins and main configurations of particle-core states can be deduced from their γ-decay. The J π = ( 3 2 − , 5 2 − or 7 2 − , 11 2 − , 15 2 − ) members of the g 9 2 ⊗3 − multiplet could be located. A systematic manner of doublet splitting is found for the lowest states with main configuration ( p 1 2 ) −1 ⊗3 210 Pb (0 + , 2 + , 4 + , 6 + , 8 + ) . A new decay branch of the g 7 2 single-particle state is attributed to an admixture of quadrupole core vibration.

The 208Pb(α, 3He) 209Pb reaction at 58 MeV

The 208 Pb(α, 3 He) 209 Pb reaction at 58 MeV has been used to search for high-spin states in 209 Pb. Only three levels are excited with appreciable intensity: the ground state (2 g 9 2 ) and levels at 0.781 ( li 11 2 ) and 1.426 MeV ( lj 15 2 ) . The angular distributions for these levels have been measured and analyzed using standard DWBA calculations to obtain spectroscopic strengths. The 208 Pb(α, α) elastic scattering was measured and optical parameters deduced from the data. A normalization value N = 50 yields spectroscopic values which are close to the values measured in the (d, p) reaction. The (α, 3 He) reaction should easily pick out any appreciable components of the j 15 2 shell model state, which weak-coupling calculations predict should be fragmented. However only three weak transitions previously seen in a (d, p) experiment are observed.

Excitation of two-particle-one-hole states by the 208Pb(d, p) 209Pb reaction

Abstract The weak transitions in the 208 Pb(d, p) 209 Pb reaction leading to two-particle-one-hole (2p-1h) states in 209 Pb have been studied at a bombarding energy of 20 MeV. These transfers exhibit typical stripping-type angular distributions and were analyzed using standard DWBA for l -values and spectroscopic factors. Arguments are presented which support an interpretation of these results as one-step transfer reactions proceeding in some cases via single-particle admixtures in the final states and in other cases via 2p-2h correlations in the 208 Pb ground state. The results imply a departure of 208 Pb from shell closure in qualitative agreement with the magnitude and character predicted by RPA calculations. Four fragments which exhaust most of the available j 15 2 single-particle strength are observed. Evidence is also obtained for fragments of single-particle strength from the N > 184 shell mixed into low-lying states of primary 2p-1h configuration. The observed levels are compared with the 209 Pb level structure predicted by calculations based on a hole coupled to the multipole pairing states in 210 Pb and a particle coupled to particle-hole excitations in 208 Pb.

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.

Study of the reactions [formula omitted] and [formula omitted] near the coulomb barrier

Abstract The vector analyzing power and differential cross section have been measured at a deuteron energy of 12.3 MeV for 208 Pb ( d , p ) , transitions to seven states of 209 Pb ( E x = 0.0, 0.79, 1.42, 1.56, 2.01 and 2.47+2.51 MeV, for 208 Pb ( d , t ) transitions to three states 207 Pb ( E x = 0.0, 0.57 and 0.89 MeV), and for 208 Pb ( d , d ) . Two deuteron optical model potentials were obtained from analysis of the elastic scattering measurements, and were used in a DWBA analysis of the present transfer-reaction results and of previous results for 207 Pb ( d , p 0 ) 208 Pb . The sensitivity of the DWBA analysis to the nuclear interior is investigated. The relative importance of Coulomb and of nuclear distortions is discussed. The sign of the vector analyzing power for given l n depends on j n and on Q -value for both the ( d, p ) and the ( d,t ) reactions. The Q -dependence invalidates the simple rule proposed by Griffith and Roman to relate j n to the predominant sign of iT 11 . Comparison of the measurements and DWBA predictions for iT 11 ( θ ) allows unambiguous determination of j n for all transitions except 207 Pb ( d , p 0 ) . All spins determined in the present work confirm previous assignments. The vector analyzing powers for the 208 Pb ( d , t 0 ) 207 Pb and 207 Pb ( d , p 0 ) 208 Pb transitions are observed to be similar in angular dependence but opposite in sign at all angles. The sign reversal reflects differences in the distortions of the proton and triton waves.

Particle-core coupling in the lead region

Abstract Several nuclei in the neighbourhood of 208Pb have been studied in terms of the core-particle coupling model. The present studies include the high-lying negative-parity states in 209Pb and positive-parity states in 209Bi, the levels of 207Bi, the low-lying negative-parity states of 205Pb and the high-lying positive-parity states of 205Pb. The results are compared with the results of single-nucleon and double-nucleon transfer reactions.

A comparison between two methods for the solution of the Lane equations

Abstract Scattering amplitudes for elastic proton scattering from the isospin-dependent local Lane potential are calculated by exact numerical integration and in a one-level approximation using the Green function techniques. As an example, scattering from 208 Pb is considered around resonances which are analogues of single-particle bound states in 209 Pb. Close agreement is found between scattering amplitudes calculated with the two methods. Tables of calculated S -matrix elements, which are useful for checking purposes, are given. The parameters for resonances such as analogue resonances are determined from an analytic pole-expansion of the scattering amplitude; this method is particularly useful in combination with the exact numerical integration method.

A study of the reactions208Pb(d, d)208Pb and208Pb(d, p)209Pb at energies above and below the Coulomb barrier

The reactions208Pb(d, d)208Pb and208Pb(d, p)209Pb have been studied in the energy region from below to above the Coulomb barrier. An optical-model analysis of the elastic scattering results has been performed to obtain parameters for a DWBA analysis. Distorted wave calculations for the direct transitions leading to single-particle states in209Pb have been used to extract spectroscopic factors. Only two deuteron potential sets give a good account of the stripping data throughout the energy region studied.

The reactions 207,208Pb(t,p) 209,210Pb and the two-particle-one-hole states of 209Pb

Abstract The reactions 207,208Pb(t, p)209,210Pb were investigated at 13 MeV bombarding energy. In 210Pb, a total of 35 levels was excited below Ex = 4.7 MeV, and in 209Pb a total of 31 levels was identified below Ex = 4.6 MeV. In the latter nucleus, all of the seven single-neutron states were observed. States at 2.16, 2.74, 2.87 and 2.91 MeV are indentified as two-particle-one-hole states of 209Pb. The transition to the 2.16 MeV level has L = 0, whereas the three latter transitions have L = 2.