Search

High-spin states of $^{110}\mathrm{Ag}$ have been studied by in-beam $\ensuremath{\gamma}$-ray spectroscopic techniques using the fusion-evaporation reaction $^{110}\mathrm{Pd}$($^{7}\mathrm{Li}, \ensuremath{\alpha}3\mathrm{n}$)$^{110}\mathrm{Ag}$ at a beam energy of 46 MeV. The previously known level scheme of $^{110}\mathrm{Ag}$ is significantly extended and modified with the addition of 50 new $\ensuremath{\gamma}$ transitions and 21 new levels. In total, four new rotational bands are observed, among which two negative-parity coupled bands are assigned to the four-quasiparticle $\ensuremath{\pi}{g}_{9/2}^{\ensuremath{-}1}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}{({g}_{7/2}/{d}_{5/2})}^{2}$ configuration based on the quasiparticle alignment analysis and cranked shell model calculations. The properties of both bands show general agreement with the fingerprints of chiral rotation, and thus such two negative-parity bands are suggested to be candidates for near degenerate chiral doublet bands. A new decoupled $\mathrm{\ensuremath{\Delta}}I=2$ band decaying directly to the yrast band is established, and probably results from one-particle-one-hole (1p-1h) proton excitation from the ${g}_{9/2}$ orbital to the ${g}_{7/2}$ orbital across the large $Z=50$ shell gap, i.e., the 2p2h $\ensuremath{\pi}{g}_{9/2}^{\ensuremath{-}2}{g}_{7/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ configuration. In addition to, a weak positive-parity sequence consisting of magnetic dipole $(M1)$ and no $E2$ crossover transitions is also identified in the present work.

High-spin states of $^{113}\mathrm{In}$ have been populated using the $^{110}\mathrm{Pd}(^{7}\mathrm{Li},4n)^{113}\mathrm{In}$ reaction at beam energies of 38 and 50 MeV. More than 50 new $\ensuremath{\gamma}$ transitions are observed in $^{113}\mathrm{In}$. Three previously observed magnetic dipole bands are extended to higher spin states, and several new $E2$ crossover transitions within the bands are observed in two of the dipole bands. A new positive-parity $▵I=2$ band built on the $\ensuremath{\pi}{d}_{5/2}$ configuration is established. The known $▵I=2$ band is extended to $51/{2}^{+}$ state, and a gentle up-bend associated to the alignment of neutrons in the normal-parity $\ensuremath{\nu}{g}_{7/2}/{d}_{5/2}$ orbitals is found. The properties of this band are discussed based on the self-consistent tilted axis cranking relativistic mean-field model calculations. The predicted $B(E2)$, deformation parameters ${\ensuremath{\beta}}_{2}$ and $\ensuremath{\gamma}$, and ${J}^{(2)}/B(E2)$ ratios indicate that the $▵I=2$ band based on the $\ensuremath{\pi}{g}_{9/2}^{\ensuremath{-}2}{g}_{7/2}\ensuremath{\bigotimes}\ensuremath{\nu}{({h}_{11/2})}^{2}$ and $\ensuremath{\pi}{g}_{9/2}^{\ensuremath{-}2}{g}_{7/2}\ensuremath{\bigotimes}\ensuremath{\nu}{({h}_{11/2})}^{2}{({g}_{7/2}/{d}_{5/2})}^{2}$ configurations, has the characteristics of antimagnetic rotation. Furthermore, the two-shears-like mechanism for the possible antimagnetic rotational bands is examined by investigating the orientation of the angular momenta.

High-spin states in $^{92}\mathrm{Nb}$ have been investigated by using in-beam $\ensuremath{\gamma}$ ray spectroscopy with the $^{82}\mathrm{Se}(^{14}\mathrm{N},4\mathrm{n})^{92}\mathrm{Nb}$ reaction at a beam energy of 54 MeV. The positive-parity decay sequences above the previously known state ${13}^{+}$ have been extended to ${I}^{\ensuremath{\pi}}\ensuremath{\ge}({20}^{+})$ by adding nineteen new $\ensuremath{\gamma}$ rays. The level structures in $^{92}\mathrm{Nb}$ have been interpreted in terms of the shell model calculations performed in the configuration space $\ensuremath{\pi}(1{f}_{5/2},2{p}_{3/2},2{p}_{1/2},1{g}_{9/2})$ for the protons and $\ensuremath{\nu}(2{p}_{1/2},1{g}_{9/2},1{g}_{7/2},2{d}_{5/2})$ for the neutrons. The calculated results show that the inclusion of proton core excitation relative to the $Z=38$ subshell closure and neutron particle-hole excitation for the $N=50$ shell closure are essential to adequately describe the experimental high-spin states at $I\ensuremath{\approx}(18--20)\ensuremath{\hbar}$ with excitation energies above 8.5 MeV.

High-spin states of $^{138}\mathrm{Pm}$ have been populated using the $^{124}\mathrm{Te}(^{19}\mathrm{F},\phantom{\rule{0.28em}{0ex}}5\mathrm{n})^{138}\mathrm{Pm}$ reaction at a beam energy of 105 MeV. A new positive-parity side band with the same $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ configuration as that of the yrast band is observed in $^{138}\mathrm{Pm}$. The properties of the two positive-parity bands show general agreement with the fingerprints of chiral rotation and thus these two bands are suggested to be candidates for near degenerate chiral doublet bands. Besides, odd-even spin staggering of the $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ bands is studied systematically in odd-odd Cs, La, Pr, and Pm isotopes. As a result of this study we suggest that the spin value of lowest observed state of the yrast band be reassigned as 9 in $^{138}\mathrm{Pm}$. This new spin assignment is also supported by the argument of alignment additivity.

High-spin states of ${}^{126}$La have been populated using the ${}^{116}$Sn(${}^{14}$N, 4$n$)${}^{126}$La reaction at a beam energy of 77 MeV. A side band linking to the known yrast $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ band is observed. $B(M1)/B(E2)$ ratios and alignments of the side band and DCO ratios of linking transitions between the side band and the yrast band suggest that the side band has the same $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ configuration as that of the yrast band, and thus the side band is a second $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ band in ${}^{126}$La. The separation energy, $\ensuremath{\Delta}E(I)=E{(I)}_{\mathrm{side}}\ensuremath{-}E{(I)}_{\mathrm{yrast}}$, between the side band and the yrast band at the same spin, and the energy staggering parameter $S(I)$ of the second $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ band in ${}^{126}$La are compared to those of other odd-odd La isotopes. The variation trends of $\ensuremath{\Delta}E(I)$ and $S(I)$ both suggest that it is reasonable to interpret the second $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ band in ${}^{126}$La as an excited $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ band as proposed for ${}^{124}$La rather than to interpret it as a partner band of a near degenerate chiral doublet band as done for ${}^{128\ensuremath{-}134}$La.

Previous to the present study, three isolated rotational bands with tentative spin assignments had been reported in the literature and the authors estimated that, to meet the predicted alignments, the spin of these bands has to be increased by $4\ensuremath{\hbar}$ to 5$\ensuremath{\hbar}$. Based on the linking transitions observed in the present work, through the reaction ${}^{118}$Sn(${}^{14}$N,4n)${}^{128}$La, and the ${I}^{\ensuremath{\pi}}={5}^{+}$ assignment for the bandhead of the yrast band proposed by Hayakawa, Lu, Mukai, Saitoh, Hasimoto, Komatsubara, and Furuno [Z. Phys. A 352, 241 (1995)] from $\ensuremath{\beta}$-decay studies, the spins of these bands are reassigned. The alignments of bands in ${}^{128}$La deduced from the present spin assignments are consistent with the alignments of relevant bands observed in neighboring odd-$A$ nuclei ${}^{127}$La, ${}^{127}$Ba, and ${}^{131}$La. Additionally, a new band with a tentative configuration assignment $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}{d}_{3/2}$ is reported.

The candidate chiral doublet bands in ${}^{128}$La have been searched for through the ${}^{118}$Sn(${}^{14}$N, 4n)${}^{128}$La reaction at a beam energy of 69 MeV. A positive-parity sideband with the same configuration as that of the yrast band has been identified. The positive-parity and spins of the sideband have been assigned based on the $\ensuremath{\Delta}I=1$ mixed $M1/E2$ and $E2$ characters of the linking transitions between the sideband and the yrast band. The properties of the sideband and the yrast band are discussed. The newly identified sideband and the yrast band are suggested to form the candidate of the near degenerate chiral doublet bands.