C. Wu

A new short-lived neutron-deficient isotope ^{220}Np was synthesized in the fusion-evaporation reaction ^{185}Re(^{40}Ar,5n)^{220}Np at the gas-filled recoil separator SHANS. Based on the measurement of the correlated α-decay chains, the decay properties of ^{220}Np with E_{α}=10040(18) keV and T_{1/2}=25_{-7}^{+14} μs were determined, which are in good agreement with theoretical predictions. From the new experimental results coupled with the recently reported α-decay data of ^{219,223}Np, the α-decay systematics for Np isotopes around N=126 was established, which allows us for the first time to test the robustness of the N=126 shell closure in Z=93 Np isotopes. The results also indicate that, in the region of nuclei with Z≥83, the proton drip line has been reached for all odd-Z isotopes up to Np.

β-delayed one-proton emissions of ^{22}Si, the lightest nucleus with an isospin projection T_{z}=-3, are studied with a silicon array surrounded by high-purity germanium detectors. Properties of β-decay branches and the reduced transition probabilities for the transitions to the low-lying states of ^{22}Al are determined. Compared to the mirror β decay of ^{22}O, the largest value of mirror asymmetry in low-lying states by far, with δ=209(96), is found in the transition to the first 1^{+} excited state. Shell-model calculation with isospin-nonconserving forces, including the T=1, J=2, 3 interaction related to the s_{1/2} orbit that introduces explicitly the isospin-symmetry breaking force and describes the loosely bound nature of the wave functions of the s_{1/2} orbit, can reproduce the observed data well and consistently explain the observation that a large δ value occurs for the first but not for the second 1^{+} excited state of ^{22}Al. Our results, while supporting the proton-halo structure in ^{22}Al, might provide another means to identify halo nuclei.

Abstract Eclogites and granulites are fossil records of orogenies and provide crucial evidence of geodynamic processes. Incomplete knowledge on both hampers the establishment of detailed tectonothermal models for the central Himalaya. Utilizing detailed petrography, pseudosection modelling, mineral thermometers, and zircon petrochronology, the granulitized eclogites discovered firstly at Yadong region at the southern tip of the Yadong–Gulu Rift record five metamorphic stages. The epidote–amphibole eclogite facies metamorphism (M1) is preserved in the garnet core including the relics of omphacite. The peak eclogite facies metamorphism (M2) is represented by the garnet rim and melt‐related polymineralic inclusions. From M1 to M2, the eclogites experienced a prograde path from 1.7 GPa/620°C to 2.1 GPa/750–770°C. The clockwise pressure–temperature path, the occurrence as coherent layers in gneiss, and zircon U–Pb dating imply that the Indian crust subducted to a maximum depth of ~60 km in the central Himalaya, close to the Moho of southern Lhasa block at c . 17 Ma. Afterwards, the exhumation started with decompressional heating. In the high‐pressure granulite facies metamorphism (M3), almost all the omphacite broke down to the symplectites of diopside and plagioclase. The subsequent two‐pyroxene granulite facies metamorphism (M4) is characterized by the intergrowth of clinopyroxenes and orthopyroxenes, high‐Ti amphibole, and antiperthite. The exhumed eclogites eventually reached ultrahigh‐temperature conditions of ~0.8 GPa/950–1,000°C in M4 and were near completely transformed into mafic granulites. At the final stage, these granulitized eclogites cooled in the middle crust to amphibolite facies (M5) of 0.6 GPa/700–750°C. Given the spatio‐temporal consistencies between the granulitized eclogites, post‐collisional magmatism, and north‐trending rifts, the heat source of the ultrahigh‐temperature metamorphism was attributed to the upwelling of asthenospheric mantle due to slab tear of subducted Indian lithosphere. The granulitized eclogites from Yadong evolved from the high‐pressure eclogite to the ultrahigh‐temperature granulite facies, which recorded the transitions from collisional convergence to post‐collisional extension during their exhumation.

The $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$-ray spectroscopy of neutron-rich $^{123,125}\mathrm{Ag}$ isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN, and the long-predicted $1/{2}^{\ensuremath{-}}$ $\ensuremath{\beta}$-emitting isomers in $^{123,125}\mathrm{Ag}$ are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest $9/{2}^{+}$ and $1/{2}^{\ensuremath{-}}$ levels is extended in Ag isotopes up to $N=78$, providing a clear signal for the reduction of the $Z=40$ subshell gap in Ag towards $N=82$. Shell-model calculations with the state-of-the-art ${V}_{\mathrm{MU}}$ plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in $^{123,125}\mathrm{Ag}$. The tensor force is found to play a crucial role in the evolution of the size of the $Z=40$ subshell gap. The observed inversion of the single-particle levels around $^{123}\mathrm{Ag}$ can be well interpreted in terms of the monopole shift of the $\ensuremath{\pi}1{g}_{9/2}$ orbitals mainly caused by the increasing occupation of $\ensuremath{\nu}1{h}_{11/2}$ orbitals.