Experimental Spectroscopic Factors Research Articles

Diverse mechanisms in proton knockout reactions from the Borromean nucleus ^{17}text {Ne}

Nucleon knockout experiments using beryllium or carbon targets reveal a strong dependence of the quenching factors, i.e., the ratio (hbox {R}_{textrm{s}}) of theoretical to the experimental spectroscopic factors (hbox {C}^2{textrm{S}}), on the proton-neutron asymmetry in the nucleus under study. However, this dependence is greatly reduced when a hydrogen target is used. To understand this phenomenon, exclusive ^{1}text {H}(^{17}text {Ne},2hbox {p}~^{16}text {F}) and inclusive ^{12}text {C}(^{17}text {Ne},2hbox {p}~^{16}text {F})hbox {X}, ^{12}text {C}(^{17}text {Ne},^{16}text {F})hbox {X} as well as ^{1}text {H}(^{17}text {Ne},^{16}text {F})hbox {X} (X-denotes undetected reaction products) reactions with ^{16}text {F} in the ground and excited states were analysed. The longitudinal momentum distribution of ^{16}{textrm{F}} and the correlations between the detached protons were studied. In the case of the carbon target, there is a significant deviation from the predictions of the eikonal model. The eikonal approximation was used to extract spectroscopic factor values hbox {C}^2{textrm{S}}. The experimental hbox {C}^2hbox {S} value obtained with C target is markedly lower than that for H target. This is interpreted as rescattering due to simultaneous nucleon knockout from both reaction partners, ^{17}text {Ne} and ^{12}text {C}.

Core of F25 studied by the F25(−p ) proton-removal reaction

The $^{9}\mathrm{Be}(^{25}\phantom{{}^{B}e}\mathrm{F}(5/{2}^{+}),^{24}\phantom{{}^{B}e}\mathrm{O}$)X proton-removal reaction was studied at the NSCL using the S800 spectrometer. The experimental spectroscopic factor for the ground-state to ground-state transition indicates a substantial depletion of the proton ${d}_{5/2}$ strength compared to shell-model expectations, similar to the findings of an inverse-kinematics $(p,2p)$ measurement performed at RIBF. The $^{25}\phantom{{}^{B}e}\mathrm{F}$ to $^{24}\phantom{{}^{B}e}\mathrm{O}$ ground-states overlap is considerably less than anticipated if the core nucleons behaved as rigid, doubly-magic $^{24}\phantom{{}^{B}e}\mathrm{O}$ within $^{25}\phantom{{}^{B}e}\mathrm{F}$. We interpret the new results within the framework of the Particle-Vibration Coupling (PVC) model, of a ${d}_{5/2}$ proton coupled to a quadrupole phonon of an effective core. This approach provides a good description of the experimental data, requiring an effective $^{24}\phantom{{}^{B}e}\mathrm{O}^{*}$ core with a phonon energy of $\ensuremath{\hbar}{\ensuremath{\omega}}_{2}$= 3.2 MeV and a $B(E2)\ensuremath{\approx}2.7$ W.u. -- softer and more collective than a bare $^{24}\phantom{{}^{B}e}\mathrm{O}$. Both the Nilsson deformed mean field and the PVC models appear to capture the properties of the effective core of $^{25}\phantom{{}^{B}e}\mathrm{F}$, suggesting that the additional proton polarizes $^{24}\phantom{{}^{B}e}\mathrm{O}$ in such a way that it becomes either slightly deformed or a quadrupole vibrator.

Uncertainty Quantification of the Experimental Spectroscopic Factor from Transfer Reaction Models

We study the uncertainty stemming from different theoretical models in the spectroscopic factors extracted from experiments. We use three theoretical approaches, the distorted wave Born approximation (DWBA), the adiabatic distorted wave approximation (ADWA) and the continuum discretized coupled-channels method (CDCC), and analyze the 12C(d, p)13C, 14C(d, p)15C reactions. We find that the uncertainty associated with the adopted theoretical models is less than 20%. We also investigate the contribution from the remnant term and observe that it gives less than 10% uncertainty. We finally make an attempt to explain the discrepancy in the spectroscopic factors of $$^{17}C(\frac{3}{2}^+)$$ between the ones extracted from experiments and from shell model calculations by analyzing the 16C(d, p)17C reaction.

Spectroscopic factor and proton formation probability for the d3/2 proton emitter 151mLu

The quenching of the experimental spectroscopic factor for proton emission from the short-lived d3/2 isomeric state in 151mLu was a long-standing problem. In the present work, proton emission from this isomer has been reinvestigated in an experiment at the Accelerator Laboratory of the University of Jyväskylä. The proton-decay energy and half-life of this isomer were measured to be 1295(5) keV and 15.4(8) μs, respectively, in agreement with another recent study. These new experimental data can resolve the discrepancy in the spectroscopic factor calculated using the spherical WKB approximation. Using the R-matrix approach it is found that the proton formation probability indicates no significant hindrance for the proton decay of 151mLu.

Spectroscopic factor strengths using ab initio approaches

We have calculated the spectroscopic factor strengths for the one-proton and one-neutron pick-up reactions $^{27}$Al($d$,$^{3}$He)$^{26}$Mg and $^{27}$Al($d$,$t$)$^{26}$Al within the framework of the shell model. We employed two different $ab ~ initio$ approaches : an in-medium similarity renormalization targeted for a particular nucleus, and the coupled- cluster effective interaction. We also compared our results with recently determined experimental spectroscopic factors.

Even-odd staggering of the spectroscopic factor as new evidence forαclustering

We evidence a staggering effect of the experimental spectroscopic factors corresponding to even-even and odd-mass (odd-mass and odd-odd) $\ensuremath{\alpha}$ emitters. The comparison to the theoretical estimate within the standard Bardeen-Cooper-Schrieffer (BCS) approach reveals a similar staggering, but with a different behavior. It turns out that the ratio between corresponding experimental and theoretical spectroscopic factors is proportional to the experimental reduced decay width. A similar dependence was found in a previous work between the strength of the quadrupole-quadrupole $\ensuremath{\alpha}$-core interaction, describing the $\ensuremath{\alpha}$-decay fine structure and the reduced width. Thus, the even-odd staggering effect in the spectroscopic factor is a new evidence of the $\ensuremath{\alpha}$-clustering phenomenon in medium and heavy nuclei.

Shell-model study of single-neutron strength fragmentation in137Xe

We have performed shell-model calculations for the nucleus $^{137}$Xe, which was recently studied experimentally using the $^{136}$Xe($d,p$) reaction in inverse kinematics. The main aim of our study has been to investigate the single-neutron properties of the observed states, focusing attention on the spectroscopic factors. We have employed a realistic low-momentum two-body effective interaction derived from the CD-Bonn nucleon-nucleon potential that has already proved quite successful in describing the spectroscopic properties of nuclei in the $^{132}$Sn region. Comparison shows that our calculations reproduce very well the experimental excitation energies and yield spectroscopic factors that come close to those extracted from the data.

Dynamics of nuclear single-particle structure in covariant theory of particle-vibration coupling: From light to superheavy nuclei

The impact of particle-vibration coupling and polarization effects due to deformation and time-odd mean fields on single-particle spectra is studied systematically in doubly magic nuclei from low-mass $^{56}\mathrm{Ni}$ up to superheavy ones. Particle-vibration coupling is treated fully self-consistently within the framework of the relativistic particle-vibration coupling model. Polarization effects due to deformation and time-odd mean field induced by odd particle are computed within covariant density functional theory. It has been found that among these contributions the coupling to vibrations makes a major impact on the single-particle structure. The impact of particle-vibration coupling and polarization effects on calculated single-particle spectra, the size of the shell gaps, the spin-orbit splittings and the energy splittings in pseudospin doublets is discussed in detail; these physical observables are compared with experiment. Particle-vibration coupling has to be taken into account when model calculations are compared with experiment since this coupling is responsible for observed fragmentation of experimental levels; experimental spectroscopic factors are reasonably well described in model calculations.

Concise methods for proton radioactivity

Concise methods are proposed to study proton radioactivity. The spectroscopic factor is obtained from relativistic mean field (RMF) theory combined with the BCS method (RMF+BCS). The assault frequency is estimated by a quantum mechanical method considering the structure of the parent nucleus. The penetrability is calculated by the WKB approximation. No additional parameters are introduced. The extracted experimental spectroscopic factors are compared with those from the calculations by the RMF+BCS, and the agreement is good, implying that the present methods work quite well for proton radioactivity. Predictions are provided for some most possible proton emissions, which may be useful for future experiments.

Measurement of conversion electrons with thePb208(p,n)Bi208reaction and derivation of the shell model proton neutron hole interaction from the properties ofBi208

Conversion electrons from Bi208 have been measured using singles and coincidence techniques with the Pb208(p,n)Bi208 reaction at 9 MeV. The new information on multipolarities and spins complements that available from recent γ-γ-coincidence studies with the same reaction [Boutachkov, Nucl. Phys. A768, 22 (2006)]. The results on electromagnetic decays taken together with information on spectroscopic factors from earlier single-particle transfer reaction measurements represent an extensive data set on the properties of the one-proton one-neutron-hole states below 3 MeV, a spectrum which is virtually complete. Comparison of the experimental observables, namely, energies, spectroscopic factors, and γ-branching ratios, with those calculated within the shell model allows extraction of the matrix elements of the shell model residual interaction. More than 100 diagonal and nondiagonal elements can be determined in this way, through a least squares fit to the experimental data. This adjustment of the interaction significantly affects the calculated properties of the γ-ray transitions. Nevertheless, the matrix elements thus obtained are remarkably similar to those of a realistic interaction calculated from free-nucleon scattering. Characteristic features of the interaction are discussed.

Survey of Ground State Neutron Spectroscopic Factors from Li to Cr Isotopes

The ground state neutron spectroscopic factors for 80 nuclei ranging in Z from 3 to 24 have been extracted by analyzing the past measurements of the angular distributions from (d, p) and (p, d) reactions. We demonstrate an approach that provides systematic and consistent values with minimum assumptions. For the 61 nuclei that have been described by large-basis shell-model calculations, most experimental spectroscopic factors are reproduced to within 20%.

In-beam and decay spectroscopy of very neutron deficient iridium nuclei

Iridium nuclei at and beyond the proton drip line have been studied via fusion evaporation reactions. A reaction of 92Mo(78Kr, p2n) at a beam energy of 360 MeV and target thickness 500 µg cm−2 was employed to study 167,167mIr. A reaction of 112Sn(58Ni, p2n) at a beam energy of 266 MeV and target thickness 500 µg cm−2 was used to study 169,169mIr. The experiments were performed at the University of Jyväskylä utilizing the RITU separator in conjunction with the focal plane GREAT spectrometer and the JUROGAM Ge array at the target position. Excited states feeding both the ground state and isomeric state in 169Ir, excited states feeding the ground state of 167Ir and the ground state alpha decay of 165Re have been observed for the first time along with excited states feeding 167mIr. Experimental spectroscopic factors and reduced widths have been obtained for the proton and alpha decay of these nuclei.

Electron momentum spectroscopy of N 2O

An electron momentum spectroscopy (EMS) study of the outer valence orbitals of N 2O is reported. The experiments were performed at impact energies of 1000, 1200, 1600 and 1800 eV by using a recently developed multichannel (e, 2e) spectrometer. The experimental momentum profiles are compared with each other to examine their impact energy dependence. The results are used for comparisons with Hartree–Fock (HF) and density functional theory (DFT) calculations using various basis sets. The HF and DFT calculations with large basis sets are in very good agreement with the measured electron momentum profiles. Experimental spectroscopic factors for several transitions are reported.

Electronic structures of organometallic complexes of f elements. LIII. Comparison of the experimental spectroscopic splitting factors of a magnetically diluted tetrahydrofuran adduct derived from tris(η 5-cyclopentadienyl)erbium with calculated values based on wavefunctions obtained from a parametric analysis of the absorption spectrum

The absorption spectrum of (η 5-Cp) 3Er·MeTHF ( 1) has been measured at room and low temperatures. Fitting the experimental energy levels to those obtained by the diagonalization of the energy matrices obtained from a parametric Hamiltonian resulted in 47 crystal field assignments with an r.m.s. deviation of 27.6 cm −1. The averaged values of the spectroscopic splitting factors ∣ g ‖∣=8.07 and ∣ g ⊥∣=4.41 (extracted from the 2.6 K electron paramagnetic resonance spectrum of Cp 3La 0.945Er 0.055·THF ( 2)) could be reproduced in a satisfactory manner with the wavefunction of the CF ground state obtained from these calculations. Also the experimentally determined temperature dependence of μ 2 eff of the powdered complex 1 could be simulated by using the calculated wavefunctions and eigenvalues.

L-forbiddenM1transitions and pseudospin symmetry

Pseudospin symmetry relates the l-forbidden magnetic dipole transition strengths between pseudospin partners to the magnetic moments of the involved states. These relations are tested against experimental data after correction for the fragmentation of the single particle strengths. Within typical uncertainties of the experimental spectroscopic factors good agreement is found for a wide range of shell closures $Z=20--82, N=20\ensuremath{-}126,$ and pseudo-orbital angular momenta. Systematic deviations are observed for particle states above $N=28$ and $Z=50$ where the predicted $B(M1)$ values are about an order of magnitude too large.

Identification of a proton-emitting isomer in151Lu

An isomer of {sup 151}Lu was identified by its direct proton radioactivity. It was produced by bombardment of {sup 96}Ru with 266-MeV {sup 58}Ni from the Holifield Radioactive-Ion Beam Facility, mass separated with a recoil separator and implanted in a double-sided silicon strip detector, which provided signals to correlate each proton decay with a particular implant. The proton energy and half-life of {sup 151}Lu{sup m} were measured to be 1310(10) keV and 16(1) {mu}s, respectively. The half-life of the previously known h{sub 11/2} ground state was observed to be 80(2) ms in agreement with the previously adopted value of 88(10) ms. Comparison of the half-life of {sup 151}Lu{sup m} with WKB barrier-penetration calculations leads to the conclusion that the isomer is a d{sub 3/2} proton state. A two-potential approach predicts a half-life of 5.5{sub {minus}1.1}{sup +1.4} {mu}s which yields an experimental spectroscopic factor of 0.34{sub {minus}0.08}{sup +0.12}. {copyright} {ital 1999} {ital The American Physical Society}

A study or the 29,30Si( alpha ; alpha 0, alpha ') and 30Si( alpha ,t) reactions at Ealpha =26.6 MeV

The 29,30Si( alpha ; alpha 0, alpha ') and 30Si( alpha , t) reactions have been studied at a beam energy of 26.6 MeV. The data have been analysed assuming a presence of direct and compound reaction mechanisms. Angular distributions have been calculated using coupled channels or DWBA and Hauser-Feshbach model approaches. For the inelastic excitations quadrupole deformation parameters were found. For transfer reaction the experimental spectroscopic factors were obtained.

Study of the 13N(d,n)14O reaction cross section and its astrophysical implications for the 13N proton capture reaction.

The total cross section for the N-13(d, n)O-14g.s. reaction has been measured with N-13 radioactive beams at laboratory energies of 8.2, 12.0, 16.2, and 28.5 MeV. A spectroscopic factor of 0.9 is obtained from a distorted-wave Born approximation analysis of this transfer reaction. The astrophysical S factor for the N-13(p,gamma)O-14 reaction is calculated using the experimentally known resonance parameters for the resonant contribution and the direct-capture model with the experimental spectroscopic factor for the non-resonant contribution.

Construction of shell-model interactions for Z >~ 50, N >~ 82 nuclei: Predictions for A=133-134 beta - decays.

Two-shell-model interactions are constructed in the model space of the five proton and six neutron orbits just above the double shell closure at $^{132}\mathrm{Sn}$. One interaction uses the two-body matrix elements calculated by Kuo and Herling for use near $^{208}\mathrm{Pb}$. For the other, the proton-proton two-body matrix elements are replaced with effective ones of Kruse and Wildenthal and selected proton-neutron matrix elements were varied in order to better reproduce the known energy spectra of $^{134}\mathrm{Sb}$. The main difficulty in this construction is the determination of the neutron single-particle energies. This determination was done by comparison of theoretical and experimental (d,p) spectroscopic factors for the N=83, Z=54, 56, and 58 isotones. The \ensuremath{\Delta}J\ensuremath{\ne}0 first-forbidden ${\mathrm{\ensuremath{\beta}}}^{\mathrm{\ensuremath{-}}}$ decays of $^{133}\mathrm{Sn}$(7/${2}^{\mathrm{\ensuremath{-}}}$), $^{134}\mathrm{Sn}$(${0}^{+}$), $^{134}\mathrm{Sb}$(${0}^{\mathrm{\ensuremath{-}}}$), and $^{134}\mathrm{Sb}$(${7}^{\mathrm{\ensuremath{-}}}$) were considered in order to exemplify the application of these interactions.

A NEW LARGE AMPLITUDE COLLECTIVE MOTION IN NUCLEI: CLUSTERS AS SOLITONS ON THE NUCLEAR SURFACE

Based on the liquid drop model, by including nonlinear terms in the hydrodynamic equations, we show that stable solitons can exist on the nuclear surface of 208 Pb or dose to it, this being the most rigid double magic spherical nucleus. The shell effects related with this nucleus lead to a new minimum in the total potential energy. In order to connect this minimum with the cluster decays, which are spontaneous decays, we choose the corresponding energy to be degenerate with the ground state minimum. A new coexistence model consisting of the usual shell model and a cluster-like model describing a soliton moving on the nuclear surface is obtained. The corresponding amplitudes describe excellently the experimental spectroscopic factors for cluster decays.