BẢN TIN KHOA HỌC

Manifestation of the divergence between antisymmetrized-moleculardynamics and container pictures of ⁹Be via ⁹Be(p, pn)⁸Be knockout reaction

Nguyen Tri Toan Phuc, Mengjiao Lyu, Yohei Chiba, Kazuyuki Ogata

Physics Letters B 819 (2021) 136466

Abstract:

We propose a new approach to probe the spatial extension of the valence neutron orbital in the ⁹Be nucleus via the ⁹Be(p,pn)⁸Be knockout reaction. This property of the nuclear molecular orbital has not been established in previous experimental studies and divergence exists between the theoretical descriptions of ⁹Be from different perspectives, i.e., the antisymmetrized molecular dynamics and the container pictures of cluster dynamics. These pictures are represented by two different well-proven microscopic models, the antisymmetrized molecular dynamics (AMD) and Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave functions. The corresponding reduced width amplitudes (RWAs) in the ⁸Be+n channel are extracted from both the AMD and THSR wave functions, and they are found to describe drastically different valence-nucleon motion, which shows the theoretical ambiguity in describing the π-orbitals in ⁹Be. Using the RWAs as input, the physical observables of the ⁹Be(p,pn)⁸Be knockout reaction are predicted by the distorted-wave impulse approximation (DWIA) framework. The magnitudes of the triple-differential cross sections (TDX) are found to be highly sensitive to the RWA input. It is concluded that the ⁹Be(p,pn)⁸Be knockout reaction could provide a feasible probing for the subtle differences between several structure models manifesting through the spatial extension of the π-orbital in the ⁹Be nucleus.

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Van Thang Nguyen, Nguyen Phong Thu Huynh , Ngoc Ba Vu, Cong Hao Le

Agricultural Water Management 243 (2021) 106453

Abstract:

Groundwater and inorganic fertilizers are regularly applied to agricultural soils, but their 226Ra content is potentially hazardous to human health and the environment. Due to irrigation and fertilization processes, 226Ra can accumulate in topsoils, and might also leach to subsoils, groundwater, and surface water. However, there are few studies on the accumulation of radium in the agricultural soils due to irrigation with groundwater. In this work, we analysed the radium content in 60 groundwater samples collected from a coastal area of Phu Yen Province, Vietnam where groundwater is regularly used for irrigation practices. Long-term accumulation of 226Ra in agricultural topsoils due to irrigation with groundwater was modelled for rice, maize, potato, and tomato top- soils. The fate of 226Ra in the topsoil (0–20 cm) was studied by using the Canadian Environmental Modelling Centre (CEMC) soil model and the HYDRUS-1D model. We found that the total inputs of 226Ra were 0.83, 2.45, 0.24, and 0.57 Bq m−2 d−1 for rice, maize, potato, and tomato soils, respectively. The total removals were 0.145, 0.236, 0.272, and 0.125 Bq m−2 d-1 found in rice, maize, potato, and tomato soils, respectively. A simple formula was developed to calculate the accumulation rate of 226Ra in the topsoil. Using this model we predict that the activity concentration of 226Ra will increase in rice, maize, and tomato soil, but will remain almost unchanged in potato soils. The accumulation rates 226Ra were 224, 791, and 115 Bq m−2 y−1. After 25 years of agricultural practices, the total activity values of 226Ra that accumulate in rice, maize, and tomato soils can reach 5147, 17278, and 2711 Bq m−2, respectively. We found the good agreements in the results based on two models. The irrigation practices with groundwater samples contribute 96.7, 79.5, and 79.8 % of 226Ra to the accumulation rates of 226Ra in rice, maize, and tomato soils, respectively.

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Levels of ²²⁶Ra in some paddy soils in the Mekong Delta region (Vietnam): current status and long-term assessment

Van Thang Nguyen, Binh An Le, Nguyen Phong Thu Huynh & Cong Hao Le

Journal of Radioanalytical and Nuclear Chemistry (2021)

Abstract:

²²⁶Ra levels in rice, soil, fertilizers, and water samples were analysed in 16 paddy fields in the Mekong Delta region. Levels of this radionuclide in the rice ecosystems caused radiation doses below the limits due to radionuclides in foodstuffs recommended by ICRP. Long-term change of ²²⁶Ra in the soil was predicted by a combination of experimental and modelling methods based on balance between its input and loss rates in topsoil. Similar results were found based on different mathematical models. The long-term increase of ²²⁶Ra found in the topsoil has not significantly changed since it has been studied ten years ago.

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Van Thang Nguyen, Nguyen Phong Thu Huynh, Cong Hao Le

Environmental Science and Pollution Research (2020)

Abstract:

Groundwater is a major source of drinking water and agricultural water in some regions of the world. However, it contains a high level of 226Ra that is potentially hazardous to human health and the environment. Normally, the activity concentration of 226Ra in groundwater is determined to assess the quality of groundwater that can be used as drinking water. There are few studies on the accumulation of 226Ra in the agricultural soil due to irrigation with groundwater. In this study, levels of 226Ra were determined on over 60 groundwater samples collected from the public water supply wells in Phu Yen province, Vietnam. Besides assessment of the health risks to population due to drinking groundwater samples, the impact of groundwater irrigation to the maize field in the study area was studied. For this purpose, two chemical fate models were applied and the comparison of their results was performed. Based on the model assessments, we predicted that the present agricultural practices increased the 226Ra activity concentration in the maize soil, and the level of 226Ra activity concentration in the topsoil can exceed the recommended level at 11.4 years of the present agricultural practices on the maize soil.

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Trần Nhân Giang, Nguyễn Tấn Được, Nguyễn Thị Mỹ Lệ, Bùi Hoàng Minh

Tạp chí Khoa học Trường Đại học Cần Thơ Tập 56, Số chuyên đề: Khoa học tự nhiên (2020)(1):90-97

Tóm tắt:

Nghiên cứu này được thực hiện nhằm khảo sát khả năng phục hồi ảnh của thuật toán tích chập trong phương pháp chụp ảnh nhiễu xạ sử dụng tia X kết hợp không hoàn toàn. Nghiên cứu được thực hiện bằng việc sử dụng chùm tia X tới với các mức độ kết hợp khác nhau và các loại mẫu khác nhau nhằm khảo sát khả năng phục hồi ảnh của thuật toán tích chập ở những điều kiện khác nhau. Kết quả đạt được trong nghiên cứu này cho phép đánh giákhả năng áp dụng của thuật toán tích chập trong phương pháp chụp ảnh nhiễu xạ sử dụng tia X kết hợp không hoàn toàn.

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Investigation of the ground-state spin inversion in the neutron-rich $47, 49 Cl$ isotopes

B. D. Linh, N.T.T.Phuc et al.

Phys. Rev. C 104, 044331

Abstract:

A first $γ$ -ray study of $47, 49 Cl$ spectroscopy was performed at the Radioactive Isotope Beam Factory with $50 Ar$ projectiles at 217 MeV/nucleon, impinging on the liquid hydrogen target of the MINOS device. Prompt deexcitation $γ$ rays were measured with the NaI(Tl) array DALI2 $^{+}$ . Through the one-proton knockout reaction $50 Ar (p, 2 p)$ , a spin assignment could be determined for the low-lying states of $49 Cl$ from the momentum distribution obtained with the SAMURAI spectrometer. A spin-parity $J^{π} = 3 / 2^{+}$ is deduced for the ground state of $49 Cl$ , similar to the recently studied $N = 32$ isotope $51 K$ . The evolution of the energy difference $E (1 / 21^{+}) - E (3 / 21^{+})$ is compared to state-of-the-art theoretical predictions.