arXiv subjects

Yi-Fei Niu

Publications and source records attributed to Yi-Fei Niu.

5 recordsLinked to original sources

arXiv2026

Microscopic Calculation of Electric Quadrupole Effective Charges in Exotic Nuclei

Electric quadrupole ($E2$) effective charges are evaluated based on the self-consistent relativistic Hartree-Fock single-particle states, with core-polarization corrections resummed to all orders using the Tamm-Dancoff approximation (TDA). Configuration-interaction relativistic Hartree-Fock (CI-RHF) calculations employing the TDA effective charges well reproduce the $B(E2)$ strength for neon isotopes from stability to the neutron drip line. We find that polarization charges associated with continuum states are significantly quenched due to their extended density distributions and weak coupling to the core, underscoring the critical role of continuum effects in $E2$ transition evaluations for exotic nuclei. Moreover, the CI-RHF model predicts a suppressed $B(E2; 2^+_2 \to 0^+_2)$ in $^{30}$Ne, together with strong in-band $B(E2)$ strengths of the yrast band, suggesting the coexistence of a nearly spherical excited $0^+_2$ state and a deformed ground state within the $N=20$ "island of inversion".

nucl-th↗

arXiv2026

The quenching of the axial-vector coupling constant $g_A$ in $β$-decay: joint effects from chiral two-body currents and many-body correlations

In nuclear $β$-decay calculations, the axial-vector coupling constant $g_A \approx 1.27$ usually needs to be quenched phenomenologically by a factor $q~\approx$ 0.75 to reproduce {the Gamow-Teller (GT) transition strengths}. We propose a novel approach to quench the GT {strength} of $β$-decay within the microscopic random phase approximation (RPA) plus particle-vibration coupling (PVC) approach, incorporating the contributions of two-body currents (TBC) derived from chiral effective field theory ($χ$EFT). Self-consistent RPA+PVC calculations are performed in three doubly magic nuclei, $^{56}$Ni, $^{100}$Sn, and $^{132}$Sn, with various Skyrme energy density functionals, and the effect of TBC is evaluated by using the obtained many-body wavefunctions. A combined effects of the many-body correlations introduced by PVC and chiral TBC quench the GT strength and reproduce quantitatively experimental data without any additional adjustments. The extracted quenching factors $q$ by the present microscopic model lie in the range $\approx$ 0.73--0.80, which is quite close to the commonly adopted empirical value of $q \approx 0.75$.

nucl-th↗

arXiv2024

Angular Momentum-Resolved Inelastic Electron Scattering for Nuclear Giant Resonances

Giant resonances (GRs) provide crucial insights into nuclear physics and astrophysics. Exciting GRs using particles like electrons is effective, yet the angular momentum (AM) transfer of electrons, including both intrinsic spin and orbital degrees of freedom in inelastic scattering, has never been studied. Here, we investigate AM transfer in GRs excited by plane-wave and vortex electrons, developing a comprehensive AM-resolved inelastic electron scattering theory. We find that even plane-wave electrons can model-independently extract transition strengths of higher multipolarity by selecting specific AM states of scattered electrons. Additionally, relativistic vortex electrons with orbital angular momentum (OAM) $\pm1$ can be efficiently generated. Vortex electrons can also be used to extract GR transition strength as in the plane-wave case, regardless of the position of nucleus relative to the beam axis. Furthermore, relativistic vortex electrons with larger OAM can be generated for on-axis nuclei due to AM conservation. Our method offers new perspectives for nuclear structure research and paves the way for generating vortex particles.

nucl-th↗

arXiv2023

Manipulation of Giant Multipole Resonances via Vortex $γ$ Photons

Traditional photonuclear reactions primarily excite giant dipole resonances, making the measurement of isovector giant resonances with higher multipolarties a great challenge. In this work, the manipulation of collective excitations of different multipole transitions in nuclei via vortex $γ$ photons has been investigated. We develop the calculation method for photonuclear cross sections induced by the vortex $γ$ photon beam using the fully self-consistent random-phase approximation plus particle-vibration coupling (RPA+PVC) model based on Skyrme density functional. We find that the electromagnetic transitions with multipolarity $J< m_γ$ are forbidden for vortex $γ$ photons due to the angular momentum conservation, with $m_γ$ being the projection of total angular momentum of $γ$ photon on its propagation direction. For instance, this allows for probing the isovector giant quadrupole resonance without interference from dipole transitions using vortex $γ$ photons with $m_γ=2$. The electromagnetic transitions with $J>m_γ$ are strongly suppressed compared with the plane-wave-$γ$-photon case, and even vanish at specific polar angles. Therefore, the giant resonances with specific multipolarity can be extracted via vortex $γ$ photons. Moreover, the vortex properties of $γ$ photons can be meticulously diagnosed by measuring the nuclear photon-absorption cross section. Our method opens new avenues for photonuclear excitations, generation of coherent $γ$ photon laser and precise detection of vortex particles, and consequently, has significant impact on nuclear physics, nuclear astrophysics and strong laser physics.

nucl-th↗

arXiv2022

Constraining equation of state of nuclear matter by charge-changing cross section measurements of mirror nuclei

The nuclear symmetry energy plays a key role in determining the equation of state (EoS) of dense, neutron-rich matter, which connects the atomic nuclei with the hot and dense matter in universe, thus has been the subject of intense investigations in laboratory experiments, astronomy observations and theories. Various probes have been proposed to constrain the symmetry energy and its density dependence. Currently, the extensive data yield already a good and consistent constraint to the symmetry energy ($E_\text{sym}(ρ)$) at saturation density, but do not yet give a consistent result of one critical EoS parameter, $L$, the density dependence of the symmetry energy. In this work, we report a new probe of $L$ at saturation density. A good linear correlation is found between $L$ and the charge changing cross section difference ($Δσ_\text{cc}$) of mirror nuclei $^{30}$Si-$^{30}$S for both the Skyrme-Hartree-Fock theory (SHF) and covariant (relativistic) density functionals (CDF). We found that the pairing effect for this mirror pair is essential to get a consistent correlation between $L$ and $Δσ_\text{cc}$ in both the SHF and CDF. Here, the cross sections are calculated on the same target and at the same energy using the zero-range optical-limit Glauber model. The linearity is found to be in the same precision as those found between $L$ and neutron skin thickness or proton radius difference.

nucl-th↗