pISSN 0374-4914 eISSN 2289-0041
• ### Research Paper 2020-07-31

#### Study of the Scintillation Properties of a CsI:Tl Crystal and Pulse Shape Discrimination Study

Sang Hyeok IM, HongJoo KIM*, Phan Quoc VUONG

Abstract : Scintillators are widely used in and studied for particle physics, nuclear physics and astroparticle physics detection. In this study, we estimated the scintillation properties of a CsI:Tl crystal and determined the best method to discriminate $\alpha$-particles, which is an important component of the cosmic-ray background, from $\gamma$-rays. We studied the scintillation properties of the CsI:Tl crystal and the pulse shape discrimination capability by using an $^{241}$Am $\alpha$-particle source and a $^{137}$Cs $\gamma$-ray source. For the pulse shape discrimination study, we used these well-known methods: the mean time method, charge integration method and optimum filter method. To determine which method was best for discrimination, we calculated the FOM value for each method under various conditions. Consequently, the optimum filter method was found to give the best value of the FOM. If we use the optimum filter method when we are observing $\gamma$-rays from the sky, we can distinguish the background of ion particles, such as $\alpha$-particles, from $\gamma$-rays.

• ### 2020-07-31

#### Dependences Comparison of the Polarization Spectroscopy Signal on Pump Beam Intensity and Temperature for closed transition lines of $^{85}\text{Rb}$ and $^{87}\text{Rb}$

Jeongyoun JEONG, Sanglok LEE, Geol MOON*

Abstract : We investigate the dependence of the polarization spectroscopy signal on the pump beam intensity and the vapor cell temperature around the $F_g=3\rightarrow F_e=4$ closed transition line of $^{85}$Rb and the $F_g=2\rightarrow F_e=3$ closed transition line of $^{87}$Rb, and we analyze the amplitudes of those signals. We observe that the temperature dependences of the polarization spectroscopy signal around the closed transition lines of $^{85}$Rb and $^{87}$Rb shows different tendencies, and that the temperature dependence of the polarization spectroscopy signal on the pump beam intensity. Interestingly the different temperature dependence of two isotopes comes from the difference in energy spacing between its hyperfine structure energy levels. It was theoretically confirmed that the signal amplitude of the closed transition line is affected by overlapping with the cross-over signal due to the increase in line width of the cross-over spectral signal depending on the temperature dependence.

• ### Research Paper 2020-06-30

#### Spectroscopic Characteristics of Zn$_{1-x}$Mn$_{x}$S Thin Films by Ellipsometry and Absorptance Measurements

Dae Jung KIM, Bong Jin KIM, Duk Hyeon KIM et al.

Abstract : Zn$_{1-x}$Mn$_{x}$S thin films were grown on GaAs(100) substrates by using hot-wall epitaxy. X-ray diffraction patterns revealed the crystal structure of the epilayer. The optical properties were investigated using spectroscopic ellipsometry at 300 K from 3.0 -- 8.7 eV. The obtained data were analyzed to determine the critical points of the pseudodielectric function spectra, $\langle\varepsilon(E)\rangle=\langle\varepsilon_{1}(E)\rangle+\langle\varepsilon_{2}(E)\rangle$, such as $E_{0}/E_{0}+\Delta_{0}$, $E_{1}$, and three $E_{2}(\Sigma,\Delta,\Gamma)$structures. These critical points were determined by fitting analytical line-shapes to numerically calculated derivatives of the pseudodielectric functions. In particular, the transmittance/absorptance measurements were carried out to obtain the optical properties of the Zn$_{1-x}$Mn$_{x}$S epilayers, and the exact optical energy bandgap ($E_{g}$) was determined by comparing these results with the results of the ellipsometry measurements. Also, the energy band structures from the ellipsometry and the absorptance measurements were analyzed as a function of Mn concentration. The results obtained demonstrate that ellipsometry can be efficiently and non-destructively used to examine the energy bandgap of Zn$_{1-x}$Mn$_{x}$S epilayers.

• ### Research Paper 2020-06-30

#### Restoration of Human Activity in the Archaeological site Using Absolute Dating

Myung-Jin KIM*

Abstract : We first used radiocarbon dating, TL/OSL dating and archaeo-magnetic dating to calculate the absolute chronology of various objects excavated from the Gyesil-ri archaeological site at Gongju. After we had summarized the probability density of all absolute chronologies of each object by using the KDE model performed a peak deconvolution with a normal distribution, and found that human activity first occurred at the Gyesil-ri site in 840 $\pm$ 160 AD (1$\sigma$ SD) and continued from 1,250 $\pm$ 160 AD (1$\sigma$ SD) to 1,670 $\pm$ 180 AD (1$\sigma$ SD). Those periods correspond to the Unified Silla, Goryeo dynasty and late Chosun dynasty, respectively. Within the Gyesil-ri site, the objects related to metallic works, including the slag layer in the late Chosun dynasty period were located perpendicular to the contour lines, which means that the metallic works were carried out at higher places in the Gyesil-ri site and that slag, as well as other residuals, were naturally discarded in lower places.

• ### Research Paper 2020-05-29

#### Calculation Method of Total Energy and Atomic Interaction Potential Through Machine Learing Using a Neural Network of Atomic Structure Data

Doukyun KIM, Chul Hong PARK*

Abstract : We examined a machine learning method to extract the atom-pair interaction potential energy in materials. The data for the atomic structures and the corresponding total energies were generated by using the ab-initio molecular dynamic simulation, by which the artificial neural network (ANN) was trained to predict the total energies of the materials. Two ANNs were assigned: one to simulate (i) the dependence of the atom-pair interaction energy on the distance between the nearest atoms and the other to simulate (ii) the angular distortion energy. We found that compared to the true energies the total energies of Si could be successfully predicted with an error of about 1 meV/atom for atomic structures generated at 300 K, and that the dependence of the atomic interaction energy on the distance and the angular distortion energy could be obtained by training an ANN for atomic structures of various volumes.

## Current Issue

July, 2020 | Volume 70, No. 7
• ### Research Paper 2020-07-31

#### Optical and Surface Characteristics of TiO$_{2}$ Thin Films Deposited by using RF Magnetron Sputtering

Bong Ju LEE, Youn Saup YOON, Myung Bok LEE*

Abstract : Titanium dioxide (TiO$_{2}$) films were deposited on glass substrates by using RF magnetron sputtering, and their optical and surface properties were investigated according to the sputtering process condition. Variations in the crystal structure, surface morphology, optical spectra, and hydrophilicity of the films were characterized with changing O$_{2}$ partial pressure in an ambient gas. The grown films were amorphous, and their surface roughness decreased with increasing of O$_{2}$ partial pressure. Partial substitution of O$_{2}$ for Ar increased the optical transmittance and decreased the reflection in the wavelength range of visible light. The hydrophilicity of the film’s surface decreased with increasing O$_{2}$ partial pressure, which was considered to be the cause of the variation in the film’s surface roughness.

• ### Research Paper 2020-07-31

#### EPR Investigation of Cu$^{2+}$ Ions with CuO Content in Na$_{2}$O-B$_{2}$O$_{3}$-CuO Glasses

Young Hoon KIM, Tae Ho NOH, Seung Kee SONG*

Abstract : Glasses of the composition $x$Na$_{2}$O-B$_{2}$O$_{3}$-$y$CuO ($x$ = Na$_{2}$O mol% / B$_{2}$O$_{3}$ mol% and $y$ = CuO mol% / B$_{2}$O$_{3}$ mol%) with $x$ = 0.1, 0.3 and $y$ = 0.01 -- 0.07 were prepared using the conventional melt quenching method. EPR (electron paramagnetic resonance) spectral studies of Cu$^{2+}$ ions in the glasses were carried out. From the EPR spectra, the spin Hamiltonian parameters were obtained at room temperature, and the structural variation around Cu$^{2+}$ ions with CuO content were analyzed. EPR data indicate that the ground state of the Cu$^{2+}$ ions in the glass samples is $d_{x^2-y^2}$ orbital ($^{2}$B$_{1g}$ state) and that the Cu$^{2+}$ ions are located in the distorted octahedral site ($D_{4h}$) with tetragonally elongated symmetry along the $z$-axis. Values of $\Delta g$ and $\Delta g_{\parallel}/A_{\parallel}$ with increasing CuO content in the samples with $x$ = 0.1 and 0.3 slightly decreases, indicating that the tetragonal symmetry distortion of the ligand field around the Cu$^{2+}$ ions in the octahedral [CuO$_{6}$] complex decreases. With increasing in CuO content, the values of the optical basicity ($\Lambda_{th}$) slightly increase, which seems to be related with the creation of non-bridging oxygens (NBOs) around the Cu$^{2+}$ ions as Cu$^{2+}$ ions are introduced in to the glass network. With increasing Na$_{2}$O content, the values of the spin Hamiltonian parameters change and the $\Delta g$ and the $g_\parallel/A_\parallel$ values decreases which leads to a decrease the distortion of the ligand field around the Cu$^{2+}$ ions. The values of the optical basicity increase as the Na$_{2}$O content in the glasses is increased.

• ### Research Paper 2020-07-31

#### Vacuum Structure in the Standard Model with a Complex Scalar Singlet

Jae Sik LEE, Jubin PARK*

Abstract : We analyze the vacuum structure in an extension of the Standard Model with a complex singlet scalar field. Beyond the Standard Model, this model shows a much richer vacuum structure and a variety of interesting mass spectra. In this paper, we first show that the Higgs mass matrix can be simplified using the proper basis, and it can comprehensively reflect the change in the tadpole conditions due to the soft symmetry-breaking terms. Thus, this framework makes it easy to obtain a mass matrix through the corresponding tadpole conditions when considering new symmetry such as $\mathbb{Z}^\prime_2$. Finally, we introduce the Higgs potential for the trilinear and quartic Higgs self couplings, and summarize the vacuum structure taking into account all possible cases with a corresponding set of inputs and miscellaneous relations.

• ### Research Paper 2020-07-31

#### Study of the Scintillation Properties of a CsI:Tl Crystal and Pulse Shape Discrimination Study

Sang Hyeok IM, HongJoo KIM*, Phan Quoc VUONG

Abstract : Scintillators are widely used in and studied for particle physics, nuclear physics and astroparticle physics detection. In this study, we estimated the scintillation properties of a CsI:Tl crystal and determined the best method to discriminate $\alpha$-particles, which is an important component of the cosmic-ray background, from $\gamma$-rays. We studied the scintillation properties of the CsI:Tl crystal and the pulse shape discrimination capability by using an $^{241}$Am $\alpha$-particle source and a $^{137}$Cs $\gamma$-ray source. For the pulse shape discrimination study, we used these well-known methods: the mean time method, charge integration method and optimum filter method. To determine which method was best for discrimination, we calculated the FOM value for each method under various conditions. Consequently, the optimum filter method was found to give the best value of the FOM. If we use the optimum filter method when we are observing $\gamma$-rays from the sky, we can distinguish the background of ion particles, such as $\alpha$-particles, from $\gamma$-rays.

• ### Research Paper 2020-07-31

#### Exploring PCK Change of the high School Physics Teachers for Special Relativity Through Developing and Discussing CoRe

Soyun KIM, Jiyeong MUN, Sung-Won KIM*

Abstract : In order to develop and support the physics teachers’ Pedagogical Content Knowledge (PCK) on special relativity theory, a new concept introduced in the 2009 revised curriculum, we explored how teachers’ PCK changes through CoRe development and discussion experience. Specific research questions are as follows: First, to what extent do physics teachers’ PCK change through the development and the discussion of CoRe? Second, which elements of the PCK emerge during the discussion of CoRe?, Third, what is the physics teachers’ perception of the CoRe development and discussion experience? Four high school physics teachers participated in this study. We collected developed CoRe, discussion audio data, and individual interview data. Data analysis was based on the rubric modified and supplemented by referring to previous studies. Results indicated that teachers’ PCK scores on ‘syntactic knowledge’, ‘teaching methods’, and ‘student understanding’ were increased after CoRe development and discussion. Also, the emerging PCK elements during teacher discussion were ‘substantive knowledge’, ‘teaching method’, and ‘student understanding’. Results also indicated that the experience of developing and discussion CoRe on special relativity theory served as an opportunity for teachers to reflect on their teaching goals and reasons for doing so.

• ### Research Paper 2020-07-31

#### The Effects of Experimental Activity with Computing Thinking Expression on Elementary School Students' Scientific Models

Eunju KANG, Jina KIM*

Abstract : The purpose of this study was to investigate the effects of experimental activities applied to flowcharts corresponding to unplugged forms in computing education on scientific model generation by students. The subjects of the study were 23 comparison groups who conducted experiment activities under the guidance of teachers and 24 experiment groups who applied flowchart expressions to experiment activities. As a result of the students' scientific model test, the pre-test result did not show a significant difference between the two groups, but the post-test result showed a statistically significant difference. In addition, as a result of calculating the gain index by using the pre-post scores of the scientific model level generated by the comparison group and the experimental group, we found that the comparison group showed a low educational effect of 0.29 whereas the experimental group had a 0.67, which is a relatively high educational effect. Through this, we confirmed that the flowchart, which is an expression of computing thinking, had a positive effect on the scientific model generation by elementary school students.

• ### Research Paper 2020-07-31

#### A Consideration of Introducing the Units of Weight and Mass in Elementary School

Joonhyeong PARK, Youngseok JHUN*

Abstract : The 2015 revised science curriculum for elementary school science introduced the concept of weight as more common usage representing the amount of material instead of mass, the reason being that the mass concept is difficult to understand for elementary school students. The purpose of this study is to examine the problem caused by the use of such a nonscientific expression in official government document and to search for an alternative way of introducing the concept of weight. For this, we surveyed the opinions of science educators about this problem and analyzed the transitions of Korean science curricula. In addition, we investigated science curricula and standards of other countries related to this problem. As a result, the most common perception of science educators was to introduce both units of weight and mass scientifically in elementary school science. In the transitions of Korean science curricula, the meaning of weight has been changed from ‘the magnitude of force’ to ‘the amount of material.’ In other countries, although every country introduces concept of force in elementary school science, no country introduces the concept of mass. Only one country introduced the concept of weight. Based on these results, we discussed and suggested introducing the concept of weight within the context of a balanced force in elementary school science.

• ### Research Paper 2020-07-31

#### Driven Contact Process with Temporal Feedback

Meesoon HA*

Abstract : We investigate a directed percolation (DP)-based cyclically coupled model with branching bias, namely, the driven contact process with temporal feedback (DCP-TF). In the DCP-TF, we control not only the temporal feedback by using its memory strength and the power-law tail exponent for the incubation period of the intermediate state but also the preferred direction of branching. The CP-TF in a one-dimensional lattice exhibits continuously varying scaling behaviors, which is attributed to the long-term memory caused by the power-law type feedback. This implies that the CP-TF does not belong to the DP universality class. However, its deviation from the DP exponent is not very big. To clarify this issue, we test the relevance of the external driving to the critical behaviors of CP-TF. If it belongs to the DP universality class, the branching bias is irrelevant to its critical exponents. We find that the branching bias does affect both the region of continuously varying scaling and the value of critical decay exponent. Based on numerical results and intuitive arguments in the DCP-TF, we discuss how the universality class of the CP-TF is related to the universality class of the pair CP with diffusion.

• ### Research Paper 2020-07-31

#### $^{87}$Rb Atom Trap and Atomic Beam Generation by Using a Truncated Pyramidal Mirror

Sunyoung SEO, Eunkang KIM, Ashish Kumar SHARMA et al.

Abstract : In this study, a truncated pyramidal mirror was used to generate a magneto-optical trap (MOT) of $^{87}$Rb atoms and a continuous cooled atomic beam therefrom. The pyramidal mirror has an angle of 90$^\circ$ between facing sides, and the tip has a squarehorn shape with an 18-mm length on one side. The size of the cut is 6 mm $\times$ 6 mm. The number of trapped atoms was measured to be about 10$^7$ atoms. The mean velocity of the atomic beam inside the pyramidal mirror is 3.58 m/s - 20.8 m/s, the flux is 3.6 $\times$ 10$^7$ atoms/s - 2.1 $\times$ 10$^8$ atoms/s, the atomic beam velocity distribution is 0.73 m/s - 7.34 m/s and the atomic beam temperature is 4 mK - 323 mK, respectively. This study confirms the feasibility of miniaturization of a continuously cooled atomic beam generator and provides basic data for the commercialization of atomic precision measurement technology.

• ### 2020-07-31

#### Dependences Comparison of the Polarization Spectroscopy Signal on Pump Beam Intensity and Temperature for closed transition lines of $^{85}\text{Rb}$ and $^{87}\text{Rb}$

Jeongyoun JEONG, Sanglok LEE, Geol MOON*

Abstract : We investigate the dependence of the polarization spectroscopy signal on the pump beam intensity and the vapor cell temperature around the $F_g=3\rightarrow F_e=4$ closed transition line of $^{85}$Rb and the $F_g=2\rightarrow F_e=3$ closed transition line of $^{87}$Rb, and we analyze the amplitudes of those signals. We observe that the temperature dependences of the polarization spectroscopy signal around the closed transition lines of $^{85}$Rb and $^{87}$Rb shows different tendencies, and that the temperature dependence of the polarization spectroscopy signal on the pump beam intensity. Interestingly the different temperature dependence of two isotopes comes from the difference in energy spacing between its hyperfine structure energy levels. It was theoretically confirmed that the signal amplitude of the closed transition line is affected by overlapping with the cross-over signal due to the increase in line width of the cross-over spectral signal depending on the temperature dependence.

## Current Issue

• ### Short Review on Fe$_2$O$_3$ Polymorphs and $\varepsilon$-Fe$_2$O$_3$ Thin Films

Heon-Jung KIM*

New Phys.: Sae Mulli 2018; 68(8): 819-828
https://doi.org/10.3938/NPSM.68.819

• ### Effects of Maganese Impurity on the Crystallographic and Spin-Rotation Transitions in FeS

Engchan KIM*

New Phys.: Sae Mulli 2018; 68(8): 829-833
https://doi.org/10.3938/NPSM.68.829

• ### Fabrication of Microholes in Silicon Wafers by Using Wet-Chemical Etching

Ha Young LEE, Ji-Yeon NOH, Min Sub KWAK, Kyung-Won LIM, Hyung Soo AHN, Ji-Hoon AHN, Sam Nyung YI*, Jungho RYU†

New Phys.: Sae Mulli 2018; 68(8): 834-838
https://doi.org/10.3938/NPSM.68.834