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Register a new userCoulomb shifts and shape changes in the mass 70 region
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The technique of recoil beta tagging has been developed which allows prompt gamma decays in nuclei from excited states to be correlated with electrons from their subsequent short-lived beta decay. This technique is ideal for studying nuclei very far from stability and improves in sensitivity for very short-lived decays and for high decay Q-values. The method has allowed excited states in 78Y to be observed for the first time, as well as an extension in the knowledge of T=1 states in 74Rb. From this new information it has been possible to compare Coulomb energy differences (CED) between T=1 states in 70Br/70Se, 74Rb/74Kr, and 78Y/78Sr. The A=70 CED exhibit an anomalous behavior which is inconsistent with all other known CED. This behavior may be accounted for qualitatively in terms of small variations in the Coulomb energy arising from shape changes.
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We studied the proton-rich $T_z=-1$ nucleus $^{70}$Kr through inelastic scattering at intermediate energies in order to extract the reduced transition probability, $B(E2;;0^+ rightarrow 2^+)$. Comparison with the other members of the $A=70$ isospin triplet, $^{70}$Br and $^{70}$Se, studied in the same experiment, shows a $3sigma$ deviation from the expected linearity of the electromagnetic matrix elements as a function of $T_z$. At present, no established nuclear structure theory can describe this observed deviation quantitatively. This is the first violation of isospin symmetry at this level observed in the transition matrix elements. A heuristic approach may explain the anomaly by a shape change between the mirror nuclei $^{70}$Kr and $^{70}$Se contrary to the model predictions.
Excited states in the $T_z=-1$ nucleus $^{70}$Kr have been populated using inelastic scattering of a radioactive $^{70}$Kr beam as well as one- and two-neutron removal reactions from $^{71,72}$Kr at intermediate beam energies. The level scheme of $^{70}$Kr was constructed from the observed $gamma$-ray transitions and coincidences. Tentative spin and parity assignments were made based on comparison with the mirror nucleus $^{70}$Se. A second $2^+$ state and a candidate for the corresponding $4^+_2$ state suggest shape coexistence in $^{70}$Kr.
Within a relativistic single particle model, we calculate the Coulomb sum rule of inclusive electron scattering from $^{40}$Ca and $^{208}$Pb in quasielastic region. Theoretical longitudinal and transverse structure functions are extracted for three momentum transfers from 300 to 500 MeV/c and compared with the experimental data measured at Bates and Saclay. We find that there is no drastic suppression of the longitudinal structure function and that the Coulomb sum rule depends on nucleus in our theoretical model.
The reaction network in the neutron-deficient part of the nuclear chart around $A sim 100$ contains several nuclei of importance to astrophysical processes, such as the p-process. This work reports on the results from recent experimental studies of the radiative proton-capture reactions $^{112,114}mathrm{Cd}(p,gamma)^{113,115}mathrm{In}$. Experimental cross sections for the reactions have been measured for proton beam energies residing inside the respective Gamow windows for each reaction, using isotopically enriched $^{112}mathrm{Cd}$ and $^{114}mathrm{Cd}$ targets. Two different techniques, the in-beam $gamma$-ray spectroscopy and the activation method have been employed, with the latter considered necessary to account for the presence of low-lying isomers in $^{113}mathrm{In}$ ($E_{gamma} approx 392$~keV, $t_{1/2} approx 100$~min), and $^{115}mathrm{In}$ ($E_{gamma} approx 336$~keV, $t_{1/2} approx 4.5$~h). Following the measurement of the total reaction cross sections, the astrophysical S factors have been additionally deduced. The experimental results are compared with Hauser-Feshbach theoretical calculations carried out with the most recent version of TALYS. The results are discussed in terms of their significance to the various parameters entering the models.
Excited states of $^{80}$Br have been investigated via the $^{76}$Ge($^{11}$B, $alpha$3n) and $^{76}$Ge($^{7}$Li, 3n) reactions and a new $Delta I$ = 1 band has been identified which resides $sim$ 400 keV above the yrast band. Based on the experimental results and their comparison with the triaxial particle rotor model calculated ones, a chiral character of the two bands within the $pi g_{9/2}otimes u g_{9/2}$ configuration is proposed, which provides the first evidence for chirality in the $Asim80$ region.
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