arXiv subjects

Dongwoo Cha

Publications and source records attributed to Dongwoo Cha.

12 recordsLinked to original sources

arXiv2010

Empirical predictions of yrast energies in even-even nuclei

The lowest excitation energies of the given multipole J^pi state (the J^pi yrast energies) are given for even-even nuclei throughout the entire periodic table. The yrast energies were calculated using the recently proposed empirical formula that depends only on the mass number A, and the valence nucleon numbers Np and Nn. We provide a complete tabulation and plots of the yrast energies calculated using the empirical formula together with the ones measured for the natural parity states up to 10+ and for the unnatural parity states up to 10^+ with the hope of encouraging active study on the possible origin of the relationship between the yrast energies, as revealed by the empirical formula.

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arXiv2009

Empirical formula extended to the yrast excitation energies of the unnatural parity states in even-even nuclei

Recently, it was shown that a simple empirical formula, in terms of the mass and valence nucleon numbers, can describe the main trends of the yrast excitation energies of the natural parity states up to $10^+$ in even-even nuclei throughout the entire periodic table. The same empirical formula was applied to the yrast excitation energies of unnatural parity states including $1^+$, $2^-$, $3^+$, $4^-$, $5^+$, $6^-$, $7^+$, $8^-$, $9^+$, $10^-$, and $11^+$ in even-even nuclei. Although the overall character of the effective residual interaction for the unnatural parity states was quite different to that of the natural parity states, the same form of the empirical formula was found to hold reasonably well for the yrast excitation energies of the unnatural parity states.

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arXiv2008

Spin-dependent empirical formula for the lowest excitation energies of the natural parity states in even-even nuclei

We present an empirical expression which holds for the lowest excitation energy of the natural parity states in even-even nuclei throughout the entire periodic table. This formula contains spin-dependent factors so that it is applied to different multipole states with the same model parameters in contrast to the recently proposed empirical expression where the model parameters had to be fitted for each multipole separately.

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arXiv2008

Empirical formula applied to the lowest excitation energies of the natural parity odd multipole states in even-even nuclei

We applied our recently proposed empirical formula, a formula quite successful in describing essential trends of the lowest excitation energies of the natural parity even multipole states, to the lowest excitation energies of the natural parity odd multipole states in even-even nuclei throughout the entire periodic table. Even though the systematic behavior of the lowest excitation energies of odd multipole states is quite different from those of even multipole states, we have shown that the same empirical formula also holds reasonably well for the odd multipole states with the exception of a few certain instances.

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arXiv2008

$N_pN_n$ scheme and the valence proton-neutron interaction

We examine the common belief that the $N_pN_n$ scheme is manifested as a direct consequence of the valence proton-neutron interaction which has proven to be a dominant factor in developing collectivity in nuclei. We show that the simplification of the $N_pN_n$-plot of the lowest $2^+$ excitation energy is introduced merely because the excitation energy always decreases when the valence nucleon number becomes larger.

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arXiv2008

N_pN_n dependence of empirical formula for the lowest excitation energy of the 2^+ states in even-even nuclei

We examine the effects of the additional term of the type $\sim e^{- λ' N_pN_n}$ on the recently proposed empirical formula for the lowest excitation energy of the $2^+$ states in even-even nuclei. This study is motivated by the fact that this term carries the favorable dependence of the valence nucleon numbers dictated by the $N_pN_n$ scheme. We show explicitly that there is not any improvement in reproducing $E_x(2_1^+)$ by including the extra $N_pN_n$ term. However, our study also reveals that the excitation energies $E_x(2_1^+)$, when calculated by the $N_pN_n$ term alone (with the mass number $A$ dependent term), are quite comparable to those calculated by the original empirical formula.

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arXiv2008

Why does the recently proposed simple empirical formula for the lowest excitation energies work so well?

It has recently been shown that a simple empirical formula, in terms of the mass number and the valence nucleon numbers, is able to describe the main trends of the lowest excitation energies of the natural parity even multipole states up to $10^+$ in even-even nuclei throughout the entire periodic table. In an effort to understand why such a simple formula is so capable, we investigate the possibility of associating each term of the empirical formula with the specific part of the measured excitation energy graph.

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arXiv2007

Universal Expression for the Lowest Excitation Energy of Natural Parity Even Multipole States

We present a new expression for the energy of the lowest collective states in even-even nuclei throughout the entire periodic table. Our empirical formula is extremely valid and holds universally for all of the natural parity even multipole states. This formula depends only on the mass number and the valence nucleon numbers with six parameters. These parameters are determined easily and unambiguously from the data for each multipole state. We discuss the validity of our empirical formula by comparing our results with those of other studies and also by estimating the average and the dispersion of the logarithmic errors of the calculated excitation energies with respect to the measured ones.

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arXiv2007

N_p N_n Scheme Based on New Empirical Formula for Excitation Energy

We examine the $N_p N_n$ scheme based on a recently proposed simple empirical formula which is highly valid for the excitation energy of the first excited natural parity even multipole states in even-even nuclei. We demonstrate explicitly that the $N_p N_n$ scheme for the excitation energy emerges from the separate exponential dependence of the excitation energy on the valence nucleon numbers $N_p$ and $N_n$ together with the fact that only a limited set of numbers is allowed for the $N_p$ and $N_n$ of the existing nuclei.

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arXiv2007

Origin of $2_1^+$ Excitation Energy Dependence on Valence Nucleon Numbers

It has been shown recently that a simple formula in terms of the valence nucleon numbers and the mass number can describe the essential trends of excitation energies of the first $2^+$ states in even-even nuclei. By evaluating the first order energy shift due to the zero-range residual interaction, we find that the factor which reflects the effective particle number participating in the interaction from the Fermi orbit governs the main dependence of the first $2^+$ excitation energy on the valence nucleon numbers.

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arXiv2007

Empirical formula for the excitation energies of the first $2^+$ and $3^-$ states in even-even nuclei

We report empirical findings that a simple formula in terms of the mass number $A$, the valence proton number $N_p$, and the valence neutron number $N_n$ can describe the essential trends of excitation energies $E_x$ of the first $2^+$ and $3^-$ states in even-even nuclei throughout the periodic table. The formula reads as $E_x = αA^{-β} + \exp (- λN_p) + \exp (- λN_n)$. The parameter $β$ in the first term is determined by the mass number $A$ dependence of the bottom contour line of the excitation energy systematics. The other two parameters $α$ and $λ$ are fitted by minimizing the $χ^2$ value between the measured and calculated excitation energies. Our results suggest that the single large-$j$ shell simulation can be applied to the excitation energies of the first $2^+$ and $3^-$ states in even-even nuclei.

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arXiv1996

Implications of Recent Data on Non-mesonic Decay of Light Lambda-hypernuclei

We analyze the recent data on the non-mesonic decays of light Lambda-hypernuclei up to ^12_Lambda C using the phenomenological model of Block and Dalitz. Fitting the spin-isospin dependent Lambda N -> NN reaction rates to six data points, we predict the remaining data in reasonable consistency. We find that despite the short-range nature of the Lambda N -> NN interaction, the non-mesonic decay of p-shell hypernuclei seems to be strongly induced by the p-shell neutrons. Also, the recent data indicate that the Delta I = 1/2 rule, well proved at the hadronic level, may not be sacred in the nuclear medium and the Delta I = 3/2 interactions seem to be needed to describe the non-mesonic decays of Lambda-hypernuclei.

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