GT Transition Research Articles

Theoretical investigation of two-particle two-hole effects on spin-isospin excitations through charge-exchange reactions

Coherent one-particle one-hole (1p1h) excitations have given us effective insights into general nuclear excitations. However, the two-particle two-hole (2p2h) excitation beyond 1p1h is now recognized as critical for the proper description of experimental data of various nuclear responses. The spin-flip charge-exchange reactions $^{48}{\rm Ca}(p,n)^{48}{\rm Sc}$ are investigated to clarify the role of the 2p2h effect on their cross sections. The Fermi transition of $^{48}{\rm Ca}$ via the $(p,n)$ reaction is also investigated in order to demonstrate our framework. The transition density is calculated microscopically with the second Tamm-Dancoff approximation, and the distorted-wave Born approximation is employed to describe the reaction process. A phenomenological one-range Gaussian interaction is used to prepare the form factor. For the Fermi transition, our approach describes the experimental behavior of the cross section better than the Lane model, which is the conventional method. For spin-flip excitations including the GT transition, the 2p2h effect decreases the magnitude of the cross section and does not change the shape of the angular distribution. The $\Delta l=2$ transition of the present reaction is found to play a negligible role. The 2p2h effect will not change the angular-distributed cross section of spin-flip responses. This is because the transition density of the Gamow-Teller response, the leading contribution to the cross section, is not significantly varied by the 2p2h effect.

Self-consistent relativistic quasiparticle random-phase approximation and its applications to charge-exchange excitations

The self-consistent quasiparticle random-phase approximation (QRPA) approach is formulated in the canonical single-nucleon basis of the relativistic Hatree-Fock-Bogoliubov (RHFB) theory. This approach is applied to study the isobaric analog states (IAS) and Gamov-Teller resonances (GTR) by taking Sn isotopes as examples. It is found that self-consistent treatment of the particle-particle residual interaction is essential to concentrate the IAS in a single peak for open-shell nuclei and the Coulomb exchange term is very important to predict the IAS energies. For the GTR, the isovector pairing can increase the calculated GTR energy, while the isoscalar pairing has an important influence on the low-lying tail of the GT transition. Furthermore, the QRPA approach is employed to predict nuclear $\beta$-decay half-lives. With an isospin-dependent pairing interaction in the isoscalar channel, the RHFB+QRPA approach almost completely reproduces the experimental $\beta$-decay half-lives for nuclei up to the Sn isotopes with half-lives smaller than one second. Large discrepancies are found for the Ni, Zn, and Ge isotopes with neutron number smaller than $50$, as well as the Sn isotopes with neutron number smaller than $82$. The potential reasons for these discrepancies are discussed in detail.

High energy-resolution measurement of theSe82(He3,t)Br82reaction for double-βdecay and for solar neutrinos

A high-resolution ($^{3}\mathrm{He},t$) charge-exchange experiment at an incident energy of 420 MeV has been performed on the double beta ($\ensuremath{\beta}\ensuremath{\beta}$) decay nucleus $^{82}\mathrm{Se}$. A detailed Gamow-Teller (${\mathrm{GT}}^{\ensuremath{-}}$) strength distribution in $^{82}\mathrm{Br}$ has been extracted, which provides information to the $\ensuremath{\beta}\ensuremath{\beta}$-decay nuclear matrix elements. Three strong and isolated transitions, which are to the 75, 1484 and the 2087 keV states in $^{82}\mathrm{Br}$, are found to dominate the low-excitation region below $\ensuremath{\approx}2.1$ MeV. Above 2.1 MeV a sudden onset of a strong GT fragmentation is observed. The degree of fragmentation resembles a situation found in the neighboring $A=76$ system $^{76}\mathrm{Ge}$, whereas the observed concentration of strength in the three low-lying states is reminiscent of the heavier neighbors $^{96}\mathrm{Zr}$ and $^{100}\mathrm{Mo}$. The strong GT transition to the 75 keV $({1}^{+})$ state makes $^{82}\mathrm{Se}$ interesting for solar neutrino detection. The $^{82}\mathrm{Se}({\ensuremath{\nu}}_{e},{e}^{\ensuremath{-}})^{82}\mathrm{Br}$ solar neutrino capture rate in a nonoscillation scenario is therefore evaluated to $668\ifmmode\pm\else\textpm\fi{}12\text{(stat)}\ifmmode\pm\else\textpm\fi{}60\text{(sys)}$ SNU, and some of the advantages of using selenium for solar neutrino studies are discussed.

Gamow-Teller transitions from the14Nground state to the14Cground and excited states

Gamow-Teller transitions from the ${}^{14}\mathrm{N}$ ground state to the ${}^{14}\mathrm{C}$ ground and excited states were investigated, based on the model of antisymmetrized molecular dynamics. The calculated strengths for the allowed transitions to the ${0}^{+}$, ${1}^{+}$, and ${2}^{+}$ states of ${}^{14}\mathrm{C}$ were compared with the experimental data measured by high-resolution charge-exchange reactions. The calculated GT transition to the ${2}_{1}^{+}$ state is strong while those to the ${0}_{2,3}^{+}$ and ${2}_{2,3}^{+}$ states having dominant $2\ensuremath{\hbar}\ensuremath{\omega}$ excited configurations are relatively weak. The present calculation cannot describe the anonymously long lifetime of ${}^{14}\mathrm{C}$, though the strength of the ${}^{14}\mathrm{C}$ ground state is somewhat suppressed because of the cluster (many-body) correlation in the ground states of ${}^{14}\mathrm{C}$ and ${}^{14}\mathrm{N}$.

The (3He,t) reaction on76Ge, and the double-β-decay matrix element

A ${}^{76}$Ge(${}^{3}$He,$t$)${}^{76}$As charge-exchange experiment at an incident energy of 420 MeV has been performed with an energy resolution of 30 keV. The Gamow-Teller GT${}^{\ensuremath{-}}$ strength distribution in ${}^{76}$As, which is the intermediate nucleus in the double-beta ($\ensuremath{\beta}\ensuremath{\beta}$) decay of ${}^{76}$Ge, has been extracted. An unusually strong fragmentation of the GT${}^{\ensuremath{-}}$ strength is observed even at low excitation energies of ${E}_{x}\ensuremath{\leqslant}5\phantom{\rule{0.16em}{0ex}}\phantom{\rule{4pt}{0ex}}\mathrm{MeV}$. By combining the data with those for GT${}^{+}$ transitions from a recent ${}^{76}$Se($d$,${}^{2}$He)${}^{76}$As measurement, the nuclear matrix element for the ${}^{76}$Ge $2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay has been evaluated. A lack of correlation among the GT transition strengths feeding the same levels from the two different directions is observed. The impact on the ${}^{76}$Ge $2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay nuclear matrix element is discussed.

High-resolution study of Gamow-Teller transitions via the54Fe(3He,t)54Co reaction

The Gamow-Teller transition strengths, $B$(GT), in $pf$-shell nuclei are of interest in nuclear physics as well as in nuclear astrophysics. A high-resolution (${}^{3}\mathrm{He},t$) charge-exchange (CE) reaction was performed on the ${T}_{z}=+1$ nucleus ${}^{54}$Fe at 0${}^{\ensuremath{\circ}}$ and at an intermediate incident energy of 140 MeV/nucleon for the study of precise GT transition strengths to the final ${T}_{z}=0$ nucleus ${}^{54}$Co. By applying dispersion matching techniques for a high-quality ${}^{3}$He beam at RCNP, an energy resolution of 21 keV and an angular resolution of 5 mr were realized. The bumplike structure of the GT resonance observed in low-resolution CE reactions at around the excitation energy (${E}_{x}$) of 10 MeV was resolved in individual $L$ $=$ 0, GT states. Excitation strengths were obtained for these GT states. If the ${R}^{2}$ value that is defined by the ratio between GT and Fermi unit cross sections is known, the $B$(GT) values can be determined from the excitation strengths. For the derivation of the ${R}^{2}$ value, the ``merged analysis'' combining the GT strength distribution from the ${}^{54}$Fe(${}^{3}\mathrm{He},t$)${}^{54}$Co study and the half-life from a ${}^{54}$Ni $\ensuremath{\beta}$ decay was used, where $T=1$ isospin symmetry for $A=54$ isobars was assumed. The GT strengths were compared with a shell-model calculation using the GXPF1 interaction. The final GT states can have the isospin values $T$ $=$ 0, 1, and 2. The isospin $T$ of each GT state observed in the $8.3\ensuremath{\le}{E}_{x}\ensuremath{\le}12.0$ MeV region of the ${}^{54}$Fe(${}^{3}\mathrm{He},t$)${}^{54}$Co spectrum was identified by comparing the excitation strength with that of corresponding $M1$ state observed in a ${}^{54}$Fe($p,{p}^{\ensuremath{'}}$)${}^{54}$Fe experiment. The $B$(GT) values of the states identified to have $T=2$, in particular, are of importance for the calculation of the electron capture rates at the core-collapse stage of presupernovae. The $B$(GT) strengths were further compared with $B(M1)$ strengths measured in the ${}^{54}$Fe($e,{e}^{\ensuremath{'}}$)${}^{54}$Fe reaction. In the $M1$ excitation using an electromagnetic probe, isoscalar (IS) and isovector (IV) orbital type operators are active in addition to the IV spin type operator that mediates the GT transitions. The contributions of the IS and IV orbital terms were studied by calculating the ratio of the strengths of analogous $M1$ and GT transitions.

Theoretical investigation of the Gamow-Teller transition across N=40 shell

The Gamow-Teller transitions for pf shell nuclei with proton number less than 40 and neutron number larger than 40 were believed to be blocked, due to the full filling of the neutron orbit. However, recent experimental research shows that the Gamow-Teller transitions for these kinds of nuclei are not blocked. In this paper, we systematically calculate the GT transition of pf shell nuclei 76Se in different truncations, and the results are compared with experimental results. It is shown that, due to correlations, the believed blocked GT transition occurs, and the shell model calculations reproduce the experimental GT strength. In addition, the electron capture rates in a stellar environment are calculated and discussed.

Familial congenital cyanosis caused by Hb-M Yantai (α-76 GAC → TAC, Asp → Tyr)

Methemoglobin (Hb-M) is a rare hemoglobinopathy in China. We hereby report on a family living in Yantai, East China, with congenital cyanosis due to Hb-M mutation. The proband, a 65-year-old female, presented 63% oxygen saturation. Both Hb-M concentration and arterial oxygen saturation remained unchanged, even following intravenous treatment with methylene blue. There was also no change in blood-color (chocolate-brown) after adding 0.1% KCN. A fast-moving band (Hb-X) in hemolysates was found by cellulose acetate electrophoresis, the Hb-X/Hb-A ratio exceeding 10%. GT transition at 131nt of exon 2, although present in one of the α2 -globin alleles, was not found in α1 -globin alleles as a whole. This mutation leads to the aspartic acid to tyrosine substitution (Asp76Tyr). In this family, the novel mutation in the α2 -globin gene resulted in a rare form of congenital cyanosis due to Hb-M. This hemoglobin was named Hb-M Yantai .

Studies on the double-β decay nucleusZn64using the (d,He2) reaction

The (d,He-2) charge-exchange reaction on the double-beta decay (beta beta) nucleus Zn-64 has been studied at an incident energy of 183 MeV. The two protons in the S-1(0) state (indicated as He-2) were both momentum analyzed and detected simultaneously by the BBS magnetic spectrometer and its position-sensitive detector. He-2 spectra with a resolution of about 115 keV (FWHM) have been obtained allowing identification of many levels in the residual nucleus Cu-64 with high precision. Zn-64 is one of the rare cases undergoing a beta beta decay in beta(+) direction. In the experiment presented here, Gamow-Teller (GT(+)) transition strengths have been extracted. Together with the GT(-) transition strengths from Ni-64(He-3,t) data to the same intermediate nucleus Cu-64, the nuclear matrix elements of the beta beta decay of Zn-64 have been evaluated. Finally, the GT(+/-) distributions are compared with shell-model calculations and a critical assessment is given of the various residual interactions presently employed for the pf shell.

Unified description of the doubleβdecay to the first quadrupole phonon state in spherical and deformed nuclei

The Gamow-Teller transition operator is written as a polynomial in the dipole proton-neutron and quadrupole charge-conserving quasiparticle random-phase approximation boson operators, using the prescription of the boson expansion technique. Then, the $2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ process ending on the first ${2}^{+}$ state in the daughter nucleus is allowed through one-, two-, and three-boson states describing the odd-odd intermediate nucleus. The approach uses a single particle basis that is obtained by projecting out the good angular momentum from an orthogonal set of deformed functions. The basis for mother and daughter nuclei may have different deformations. The GT transition amplitude as well as the half-lives were calculated for 18 transitions. Results are compared with the available data as well as with the predictions obtained with other methods.

Double beta decay to the first 2+ state within a boson expansion formalism with a projected spherical single particle basis

Abstract The Gamow–Teller transition operator is written as a polynomial in the dipole proton–neutron and quadrupole charge conserving QRPA boson operators, using the prescription of the boson expansion technique of Belyaev–Zelevinski type. Then, the 2 ν β β process ending on the first 2 + state in the daughter nucleus is allowed via one, two and three boson states describing the odd–odd intermediate nucleus. The approach uses a single particle basis which is obtained by projecting out the good angular momentum from an orthogonal set of deformed functions. The bases for mother and daughter nuclei have different deformations. The GT transition amplitude as well as the half lives was calculated for eleven transitions. Results are compared with the available data as well as with some predictions obtained with other methods.

Gamow-Teller transitions in pf-shell nuclei studied in ( 3He, t) reactions

The Gamow-Teller transition strengths in pf-shell nuclei are important parameters in a presupernova model. A high resolution (He-3,t) reaction was performed from T-z = +1 nuclei (Ca-42, Ti-46, Cr-50 and Fe-14) to T-z = 0 nuclei ((SC)-S-42, V-46, Mn-50 and Co-54) at an incident energy of 140 MeV/nucleon and at 0 degrees for the precise study of GT transition strengths B(GT). To derive B(GT) values for these pf-shell nuclei, the R-2 value, the ratio between the GT and Fermi unit cross sections, was introduced. The R-2 values were studied for various mass nuclei by using the B(GT) values from beta-decay studies as standard, and the mass dependence was derived. It was found that GT strengths in these four pf-shell nuclei move to higher excitation energies as the mass number A increases. The obtained GT strength distributions were compared with shell model calculations.

Acid alpha-glucosidase deficiency: identification and expression of a missense mutation (S529V) in a Japanese adult phenotype.

We report a missense mutation in an adult Japanese patient with acid alpha-glucosidase (GAA) deficiency. A TC to GT transition at nucleotides 1585-1586, was identified. This transition resulted in an amino acid substitution of Ser-529 to Val (S529V) in exon 11. We also have demonstrated that the S529V mutation abolishes the catalytic activity of the enzyme. Our data suggest that this mutation is the cause of the clinical manifestation known as adult-onset GAA deficiency. The missense mutation described here is a new mutation, and the first identified in Japanese patients with GAA deficiency.

Correlation between the quenching of total GT + strength and the increase of E2 strength

Relations between the total β + Gamow-Teller (GT +) strength and the E2 strength are further examined. It is found that in shell-model calculations for N = Z nuclei, in which changes in deformation are induced by varying the single-particle energies, the total GT + or GT − strength decreases monotonically with increasing values of the B(E2) from the ground state to the first excited J π = 2 + state. Similar trends are also seen for the double GT transition amplitude (with some exceptions) and for the spin part of the total M1 strength as a function of B(E2).

Structure of nuclei near100Sn and the?g 9/2 ?vg 7/2 Gamow-Teller beta decays

Selected properties of the Gamow-Teller beta decay of even nuclei near100Sn have been studied. Two theoretical models were used: a self-consistent Hartree-Fock-Bogolyubov approach with the Skyrme interaction and a shell-correction model with a Woods-Saxon average field and monopole pairing residual interaction. Calculations reproduce fairly well both theQ EC values and the average energies of theI π=1+ states fed directly in the decay. It is shown that the observed energy splitting between the 1+ states cannot be associated with a stable deformation of a final doubly-odd nucleus. The calculated pairing factors are used to estimate the 0+ → 1+ GT transition strength in the neighbourhood of doubly-magic 50 100 Sn50.

ChemInform Abstract: LAYERED COMPOUNDS. LXIV. SYNTHESES AND CHARGE TRANSFER SPECTRA OF MULTILAYERED PARACYCLOPHANEQUINONES

AbstractDie aus den Komponenten (I) und (II) erhältlichen isomeren Disulfide (IIIa) und (IIIb) liefern bei der Photodesulfurierung die gleiche Verbindung (IV), die über die Stufen (Va) und (Vb) [74% Ausb. bezogen auf (IV)] in das Quartärsalz (Vc) übergefuhrt wird.

Layered Compounds. LXIV. Syntheses and Charge Transfer Spectra of Multilayered Paracyclophanequinones

Abstract Three isomeric triple-layered and two isomeric quadruple-layered charge transfer cyclophanes containing benzoquinone and dimethoxybenzene moieties have been synthesized together with two triple-layered and two quadruple-layered paracyclophanequinones. The structures of the isomers were determined by 1H- and 13C-NMR spectra and/or alternative syntheses. By comparing the CT bands of a series of dimethoxycyclophanequinones with those of the corresponding cyclophanequinones, it is concluded that the CT stabilization of multilayered dimethoxyquinones should be attributed mainly to the π-basicity of the durene ring which faces the acceptor quinone ring and partly to the decreasing π-basicity of dimethoxybenzene ring as the layer number increases. No orientational dependence of quinone and dimethoxybenzene moieties on GT transition was observed in the multilayered series.