arXiv subjects

Rong An

Publications and source records attributed to Rong An.

24 records · Page 2Linked to original sources

arXiv2021

Enhancement of electron-positron pairs in combined potential wells with linear chirp frequency

The effect of linear chirp frequency on the process of electron-positron pairs production from vacuum in the combined potential wells is investigated by computational quantum field theory. Numerical results of electron number and energy spectrum under different frequency modulation parameters are obtained. By comparing with the fixed frequency, it is found that frequency modulation has a significant enhancement effect on the number of electrons. Especially when the frequency is small, appropriate frequency modulation enhances multiphoton processes in pair creation, thus promoting the pair creation. However, the number of electrons created by high frequency oscillating combined potential wells decreases after frequency modulation due to the phenomenon of high frequency suppression. The contours of the number of electrons varying with frequency and frequency modulation parameters are given, which may provide theoretical reference for possible experiments.

quant-ph↗

arXiv2021

Neutron drip line of $Z=9-11$ isotopic chains

A recent experimental breakthrough identified the last bound neutron-rich nuclei in fluorine and neon isotopes. Based on this finding, we perform a theoretical study of $Z=9, 10, 11, 12$ isotopes in the relativistic mean field (RMF) model. The mean field parameters are assumed from the PK1 parameterization, and the pairing correlation is described by the particle number conservation BCS (FBCS) method recently formulated in the RMF model. We show that the FBCS approach plays an essential role in reproducing experimental results of fluorine and neon isotopes. Furthermore, we predict $^{39}$Na and $^{40}$Mg to be the last bound neutron-rich nuclei in sodium and magnesium isotopes.

nucl-th↗

arXiv2020

Novel ansatz for charge radii in density functional theories

Charge radii are one of the most fundamental properties of atomic nuclei characterizing their charge distributions. Though the general trend as a function of the mass number is well described by the $A^{1/3}$ rule, some fine structures, such as the evolution along the calcium isotopic chain and the corresponding odd-even staggerings, are notoriously difficult to describe both in density functional theories and ab initio methods. In this letter, we propose a novel ansatz to describe the charge radii of calcium isotopes, by adding a correction term, proportional to the number of Cooper pairs, and determined by the BCS amplitudes and a single parameter, to the charge radii calculated in the relativistic mean field model with the pairing interaction treated with the BCS method. The new ansatz yields results consistent with data not only for calcium isotopes, but also for ten other isotopic chains, including oxygen, neon, magnesium, chromium, nickel, germanium, zirconium, cadmium, tin, and lead. It is remarkable that this ansatz with a single parameter can describe nuclear charge radii throughout the periodic table, particularly the odd-even staggerings and parabolic behavior. We hope that the present study can stimulate more discussions about its nature and relation with other effects proposed to explain the odd-even staggerings of charge radii.

nucl-th↗

arXiv2018

Particle number conserving BCS approach in the relativistic mean field model and its application to $^{32-74}$Ca

A particle number conserving BCS approach (FBCS) is formulated in the relativistic mean field (RMF) model. It is shown that the so-obtained RMF+FBCS model can describe the weak pairing limit. We calculate the ground-state properties of the calcium isotopes $^{32-74}$Ca and compare the results with those obtained from the usual RMF+BCS model. Although the results are quite similar to each other, we observe an interesting phenomenon, i.e., for $^{54}$Ca, the FBCS approach can enhance the occupation probability of the $2p_{1/2}$ single particle level and slightly increases its radius, compared with the RMF+BCS model. This leads to an unusual scenario that although $^{54}$Ca is more bound with a spherical configuration but the corresponding size is not the most compact one. We anticipate that such a phenomenon might happen for other neutron rich nuclei and should be checked by further more systematic studies.

nucl-th↗

arXiv2017

Suppressing Kirkendall Void Density in Circuit Interconnections by Strain Annealing

Unpredictable Kirkendall void formation at the interface of circuit interconnections underlies degradation in electronics, yet there is a lack of effective approaches to curb the amount of these voids. Here we developed a strain-anneal method to tailor grain size distributions in the copper substrate of interconnections, and demonstrate quantitatively that not only the removal of the impurities but also an increase in the grain size of the substrates leads to an appreciable decline in the void density. The interconnections on the substrate recrystallized at a high annealing temperature show the massive porosity and the increased sensitivity of the voiding to the grain size. Our findings have broad implications for manipulation of void propensity in many other hetero-interfaces and are essential for high-performance circuit bonding in high temperature/high power electronic devices based on wide band gap semiconductors.

cond-mat.mtrl-sci↗

arXiv2017

Effective slip length of confined fluid with wavy fluid-solid interfaces

We have studied the effective slip length of confined fluid with nano-structured fluid-solid interfaces. A formula bridging the effective slip length and nano structures of the interfaces has been obtained analytically. For the application of the formula, a confined fluid with wavy fluid-solid interfaces has been studied as an example. In the study, the criteria of the formula have been detailed, and verified by the finite element method.

physics.flu-dyn↗