Jeogndo Park

Seoul National University of Science and Technology · Deparment of Design Engineering

To analyze the cause of the destruction of thin, carbon-backed lithium fluoride targets during a measurement of the fusion of ⁷Li and ¹⁷O, we estimate theoretically the lifetimes of carbon and LiF films due to sputtering, thermal evaporation, and lattice damage and compare them with the lifetime observed in the experiment. Sputtering yields and the...

Background: Electric-quadrupole (E2) strengths relate to the underlying quadrupole deformation of a nucleus and present a challenge for many nuclear theories. Mirror nuclei in the vicinity of the line of N=Z represent a convenient laboratory for testing deficiencies in such models, making use of the isospin symmetry of the systems.

Motivated primarily by the large uncertainties in the thermonuclear rate of the $^{30}$P$(p,\gamma)^{31}$S reaction that limit our understanding of classical novae, we carried out lifetime measurements of $^{31}$S excited states using the Doppler Shift Lifetimes (DSL) facility at the TRIUMF Isotope Separator and Accelerator (ISAC-II) facility. The...

Low-lying states of Cd98 have been populated by the two-nucleon removal reaction (In100,Cd98+γ) and studied using in-beam γ-ray spectroscopy at the Radioactive Isotope Beam Factory at RIKEN. Two new γ transitions were identified and assigned as decays from a previously unknown state. This state is suggested to be based on a π1g9/2−12p1/2−1 configur...

DOI:https://doi.org/10.1103/PhysRevC.103.049901

The β decay of neutron-rich In129 into Sn129 was studied using the GRIFFIN spectrometer at the ISAC facility at TRIUMF. The study observed the half-lives of the ground state and each of the β-decaying isomers. The level scheme of Sn129 has been expanded with thirty-one new γ-ray transitions and nine new excited levels, leading to a reevaluation of...

The $\beta$-decay of neutron-rich $^{129}$In into $^{129}$Sn was studied using the GRIFFIN spectrometer at the ISAC facility at TRIUMF. The study observed the half-lives of the ground state and each of the $\beta$-decaying isomers. The level scheme of $^{129}$Sn has been expanded with thirty-one new $\gamma$-ray transitions and nine new excited lev...

The level structure of Na25 and Ne22 in the high excitation energy/high spin regime was studied using γ-ray spectroscopy and Doppler shift lifetime measurements following C12(O18,αp)Na25 and C12(O18,2α)Ne22 reactions. Multiple new levels and transitions were identified in both nuclides based on γ−γ coincidence data. In Na25, evidence was found for...

A high-precision branching ratio measurement for the superallowed Fermi β+ emitter Ga62 was performed with the Gamma-Ray Infrastructure for Fundamental Investigations of Nuclei (GRIFFIN) spectrometer at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. The high efficiency of the GRIFFIN spectrometer allowed 63 γ-...

A high-precision branching ratio measurement for the superallowed Fermi $\beta^{+}$ emitter $^{62}$Ga was performed with the Gamma-Ray Infrastructure for Fundamental Investigations of Nuclei (GRIFFIN) spectrometer at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. The high efficiency of the GRIFFIN spectrometer...

Excited states of In129 populated following the β decay of Cd129 were experimentally studied with the GRIFFIN spectrometer at the ISAC facility of TRIUMF, Canada. A 480-MeV proton beam was impinged on a uranium carbide target and Cd129 was extracted using the Ion Guide Laser Ion Source (IG-LIS). β and γ rays following the decay of Cd129 were detect...

Spectroscopy of doubly magic 50132Sn82 has been performed with the GRIFFIN spectrometer at TRIUMF-ISAC following the β decay of 49132In83. The analysis has allowed for the placement of a total of 70 transitions and 29 excited states in Sn132. Detailed spectroscopy has also been performed on Sb131, resulting from the β decay of Sn131, produced from...

The low-lying structure of semimagic Sn118 has been investigated through the β decay of In118 (T1/2=4.45 min) to study shape coexistence via the reduced transition probabilities of states in the 2p-2h proton intruder band. This high-statistics study was carried out at TRIUMF-ISAC with the GRIFFIN spectrometer. In total, 99 transitions have been pla...

Excited states of $^{129}$In populated following the $\beta$-decay of $^{129}$Cd were experimentally studied with the GRIFFIN spectrometer at the ISAC facility of TRIUMF, Canada. A 480-MeV proton beam was impinged on a uranium carbide target and $^{129}$Cd was extracted using the Ion Guide Laser Ion Source (IG-LIS). $\beta$- and $\gamma$-rays follo...

Spectroscopy of doubly magic $^{132}_{50}$Sn$_{82}$ has been performed with the GRIFFIN spectrometer at TRIUMF-ISAC following the $\beta$ decay of $^{132}_{49}$In$_{83}$. The analysis has allowed for the placement of a total of 70 transitions and 29 excited states in $^{132}$Sn. Detailed spectroscopy has also been performed on $^{131}$Sb, resulting...

The low-lying structure of semi-magic $^{118}$Sn has been investigated through the $\beta$-decay of $^{118}$In ($T_{1/2}=4.45$ min) to study shape coexistence via the reduced transition probabilities of states in the 2p-2h proton intruder band. This high-statistics study was carried out at TRIUMF-ISAC with the GRIFFIN spectrometer. In total, 99 tra...

We report on new γ-ray spectroscopy results from β decays of In99 and Sn101. 30 new γ rays were observed following the β decay of In99, and inconsistencies in the literature with respect to the γ rays following the β decay of Sn101 were addressed with two confirmed cases and two new transitions. The experimental γ-ray energies, intensities, and coi...

Background: Recent developments in {\it ab initio} nuclear theory demonstrate promising results in medium- to heavy-mass nuclei. A particular challenge for many of the many-body methodologies, however, is an accurate treatment of the electric-quadrupole, $E2$, strength associated with collectivity. Purpose: In this work we present high-precision $E...

Gamma-ray spectroscopy and lifetime measurements using the Doppler shift attenuation method (DSAM) were performed on the nucleus Mg28 near the N=20 “island of inversion,” which was populated using a C12(O18,2p)Mg28 fusion-evaporation reaction to investigate the impact of shell evolution on its high-lying structure. Three new levels were identified...

A record number of 100 Sn nuclei was detected and new isotopic species toward the proton dripline were discovered at the RIKEN Nishina Center. Decay spectroscopy was performed with the high-efficiency detector arrays WAS3ABi and EURICA. Both the half-life and the β-decay end point energy of 100 Sn were measured more precisely than the literature va...

The Tz=−32 nucleus Mg21 has been studied by Coulomb excitation on Pt196 and Pd110 targets. A 205.6(1)-keV γ-ray transition resulting from the Coulomb excitation of the 52+ ground state to the first excited 12+ state in Mg21 was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half...

The island of inversion for neutron-rich nuclei in the vicinity of N=20 has become the testing ground par excellence for our understanding and modeling of shell evolution with isospin. In this context, the structure of the transitional nucleus Mg29 is critical. The first quantitative measurements of the single-particle structure of Mg29 are reporte...

The half-lives of three β-decaying states of In8249131 have been measured with the GRIFFIN γ-ray spectrometer at the TRIUMF-ISAC facility to be T1/2(1/2−)=328(15)ms, T1/2(9/2+)=265(8)ms, and T1/2(21/2+)=323(55)ms, respectively. The first observation of γ rays following the βn decay of In131 into Sn130 is reported. The β-delayed neutron emission pro...

The half-lives of three $\beta$ decaying states of $^{131}_{~49}$In$_{82}$ have been measured with the GRIFFIN $\gamma$-ray spectrometer at the TRIUMF-ISAC facility to be $T_{1/2}(1/2^-)=328(15)$~ms, $T_{1/2}(9/2^+)=265(8)$~ms, and $T_{1/2}(21/2^+)=323(55)$~ms, respectively. The first observation of $\gamma$-rays following the $\beta n$ decay of $^...

The "Island of Inversion" for neutron-rich nuclei in the vicinity of N=20 has become the testing ground par excellence for our understanding and modelling of shell evolution with isospin. In this context, the structure of the transitional nucleus 29Mg is critical. The first quantitative measurements of the single particle structure of 29Mg are repo...

A decay spectroscopy experiment on proton-rich nuclei in the vicinity of the doubly magic Sn100 was carried out at RIKEN Nishina Center. More than 20 nuclei with 43≤Z≤50 and N≤51, produced by fragmentation reactions were investigated via analyses of β-decay, βp-decay, and subsequent γ-ray data. Owing to higher statistics, the precision on the half-...

A γ-decaying isomeric state (τ1/2=197−17+19 ns) has been identified in Cd96, which is one α particle away from the last known bound N=Z nucleus, Sn100. Comparison of the results with shell-model calculations has allowed a tentative experimental level scheme to be deduced and the isomer to be interpreted as a medium-spin negative-parity spin trap ba...

Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei, GRIFFIN, is a new high-efficiency γ-ray spectrometer designed for use in decay spectroscopy experiments with low-energy radioactive ion beams provided by TRIUMF's Isotope Separator and Accelerator (ISAC-I) facility. GRIFFIN is composed of sixteen Compton-suppressed large-volume clov...

Isospin symmetry was investigated in the lower $sd$ shell by studying the $T_z$ = $-\frac{3}{2}$ nucleus ${}^{21}$Mg in Coulomb excitation on ${}^{196}$Pt and ${}^{110}$Pd targets. A 205.6(1)-keV $\gamma$-ray transition resulting from the Coulomb excitation of the $\frac{5}{2}^+$ ground state to the first excited $\frac{1}{2}^+$ state in ${}^{21}$M...

The half-lives of isotopes around the $N=82$ shell closure are an important ingredient in astrophysical simulations and strongly influence the magnitude of the second $r$-process abundance peak in the $A\sim130$ region. The most neutron-rich $N=82$ nuclei are not accessible to the current generation of radioactive beam facilities and $r$-process si...

Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei, GRIFFIN, is a new high-efficiency $\gamma$-ray spectrometer designed for use in decay spectroscopy experiments with low-energy radioactive ion beams provided by TRIUMF's Isotope Separator and Accelerator (ISAC-I) facility. GRIFFIN is composed of sixteen Compton-suppressed large-volu...

The SPectrometer for Internal Conversion Electrons (SPICE) has been commissioned for use in conjunction with the TIGRESS γ-ray spectrometer at TRIUMF's ISAC-II facility. SPICE features a permanent rare-earth magnetic lens to collect and direct internal conversion electrons emitted from nuclear reactions to a thick, highly segmented, lithium-drifted...

We report on new or more precise half-lives, β-decay endpoint energies, and β-delayed proton emission branching ratios of Pd91, Cd95, In97, and Sn99. The measured values are consistent with known mirror transitions in lighter Tz=−1/2 nuclei, shell-model calculations, and various mass models. In addition to the β-decaying (9/2+) ground state, circum...

DOI:https://doi.org/10.1103/PhysRevC.97.019901

Excited states of 122Xe were studied via the β+/EC decay of 122Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. Compton-suppressed HPGe detectors were used for measurements of γ-ray intensities, γγ coincidences, and γ-γ angular correlations. Two sets of data were collected to optimize the decays of the ground (21.2 s) and isomeric (3....

The β-decay half lives of nuclei near the r-process path are critical information required for abundance calculations, especially those near neutron number N = 82. Specifically, the nuclei below doubly-magic 132Sn are key, and play an important role in the formation and shape of the second r-process abundance peak. The half lives in this region are...

The Xe isotopes are centrally located in the Z > 50, N < 82 region that displays an extraordinarily smooth evolution of simple collective signatures. However, the collectivity of excited states in this region is poorly characterized because of a general lack of spectroscopic data for low-spin states that provide measures of collective properties su...

DOI:https://doi.org/10.1103/PhysRevC.96.049901

Half-lives and energies of γ rays emitted in the decay of isomeric states of nuclei in the vicinity of the doubly magic Sn100 were measured in a decay spectroscopy experiment at Rikagaku Kenkyusho (The Institute of Physical and Chemical Research) of Japan Nishina Center. The measured half-lives, some with improved precision, are consistent with lit...

Many-body nuclear theory utilizing microscopic or chiral potentials has developed to the point that collectivity might be dealt with in an {\it ab initio} framework without the use of effective charges; for example with the proper evolution of operators, or alternatively, through the use of an appropriate and manageable subset of particle-hole exci...

The β-decay half-lives of Cd128-130 have been measured with the newly commissioned GRIFFIN γ-ray spectrometer at the TRIUMF-ISAC facility. The time structures of the most intense γ rays emitted following the β decay were used to determine the half-lives of Cd128 and Cd130 to be T1/2=246.2(21) ms and T1/2=126(4) ms, respectively. The half-lives of t...

Precision measurements of superallowed Fermi β-decay transitions, particularly for the lightest superallowed emitters C10 and O14, set stringent limits on possible scalar current contributions to the weak interaction. In the present work, a discrepancy between recent measurements of the C10 half-life is addressed through two high-precision half-lif...

Several new isotopes, 96In, 94Cd, 92Ag, and 90Pd, have been identified at the RIKEN Nishina Center. The study of proton drip-line nuclei in the vicinity of 100Sn led to the discovery of new proton emitters 93Ag and 89Rh with half-lives in the submicrosecond range. The systematics of the half-lives of odd-Z nuclei with Tz=−1/2 toward 99Sn shows a st...

Shape coexistence between the strongly deformed ground state and the weakly deformed 02+ state in Sr98 has been a major topic of interest due to the energy difference of 215 keV, which is the smallest in all even-even nuclei. The electric monopole transition strength ρ2(E0) is an important quantity that can relate the deformation difference and the...

The nuclear structure of 122 Xe has been investigated with measurements of the β + /EC decay of 122 Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled the determination of relative B(E2) values of some low-energy transitions, and the in-band transitions of the excited 0 + bands have been observed. As a re...

A new ancillary detector, SPICE (SPectrometer for Internal Conversion Electrons) has been constructed and recently commissioned for use with radioactive ion beams at the TRIUMF-ISAC II facility. SPICE is designed to be operated in conjunction with the TIGRESS High-Purity Germanium (HPGe) spectrometer to perform combined in-beam ?-ray and internal-c...

KOBRA (KOrea Broad acceptance Recoil spectrometer and Apparatus) facility being designed at Rare Isotope Science Project in Korea will be utilized to produce rare isotope beams by employing multi-nucleon transfer reactions at about 20 MeV/nucleon for studies of nuclear structure. KOBRA will also provide high suppression of beam induced background f...

The GRIFFIN (Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei) project is a major upgrade of the decay spectroscopy capabilities at TRIUMF-ISAC. GRIFFIN will replace the 8π spectrometer with an array of up to 16 large-volume HPGe clover detectors and use a state-of-the-art digital data acquisition system. The existing ancillary det...

This study examines when and why high performers feel job dissatisfaction by focusing on role overload (resource outflow) and relative leader-member exchange compared to other members (resource inflow) from the resource flow approach. More specifically, drawing on social exchange theory (SET) and conservation of resources theory (COR), we explore h...

Drawing on costly signaling theory, this study explores the hidden motive about why people voluntarily share their tacit knowledge with others and the resultant outcome. More specifically, we theoretically and empirically show how the need for status facilitates knowledge sharing behavior and this knowledge sharing behavior ultimately leads to incr...