Programme

O.20 -- Oral, VCTP-45

Date: Wednesday, 14 October 2020

Time: 14:50 - 15:10

Online presentation

Experimental study on the nuclear level scheme in Vietnam: examples of $^{153}$Sm and $^{172}$Yb

Nguyen Ngoc Anh (1), Nguyen Xuan Hai (1), Pham Dinh Khang (2), Nguyen Quang Hung (3,4), Ho Huu Thang (1)

(1) Dalat Nuclear Research Institute, 01 Nguyen Tu Luc Street, Dalat City, Vietnam; (2) Hanoi University of Science and Technology, 01 Dai Co Viet, Hanoi 100000, Vietnam; (3) Institute of Fundamental and Applied Sciences, Duy Tan University, Ho Chi Minh city, Vietnam; (4) Faculty of Natural Sciences, Duy Tan University, Danang City, Vietnam

Experimental study on the nuclear level scheme (NLS) at the Dalat Nuclear Research Institute (DNRI), Vietnam, is presented. Within the study, a NLS is constructed based on experimental two-step gamma cascades obtained from the (n,$\gamma$) reaction using a $\gamma-\gamma$ coincidence spectrometer, namely the (n,2$\gamma$) experiment. The neutron beam, whose flux is $1.7 \times10^5$ n.cm$^{-2}.s$^{-1}$, is extracted from the Dalat Nuclear Research Reactor. Whereas, the coincidence spectrometer is self-installed [1]. The (n,2$\gamma$) experiment allows to achieve low Compton background spectra and to identify the correlated gamma transitions. The NLSs obtained for $^{153}$Sm and $^{172}$Yb reproduced a significant part of those extracted from the Evaluated Nuclear Structure Data File (ENSDF). Based on the comparison with the ENSDF library, we have deduced 18 excited levels and 126 gamma transitions of the NLS of $^{172}$Yb, as well as 61 excited levels and 365 gamma transitions of the NLS of $^{153}$Sm, as the new data [2,3]. In addition, in the case of $^{153}$Sm, we have extended the maximum excitation energy, defined as the energy threshold below which most of the excited levels are observed, to about 1.2 and 1.8 MeV for the total and partial (for the spin range of [1/2, 3/2]$\hbar$) NLSs, respectively. This achievement permit to evaluate the predictive power of various phenomenological and microscopic nuclear level density models for $^{153}$Sm. It turns out that the exact paring plus independent-particle model [4] is the best-fit one. Moreover, preliminarily result on the extraction of radiative strength function from the two-step gamma cascade intensity distribution is also shown. References 1. P.D. Khang, N.X. Hai, V.H. Tan, N.N. Dien, Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip. 634 (2011) 47–51. 2. N.A. Nguyen, X.H. Nguyen, D.K. Pham, Q.H. Nguyen, H.T. Ho, Nucl. Phys. A. 964 (2017) 55–68. 3. Nguyen Ngoc Anh, Nguyen Quang Hung, Nguyen Xuan Hai, Pham Dinh Khang, A. M. Sukhovoj, L. V. Mitsyna, Ho Huu Thang, Le Hong Khiem , Phys. Rev. C 100, 024324 (2019). 4. N. Quang Hung, N. Dinh Dang, and L. T. Quynh Huong, Phys. Rev. Lett. 118, 022502 (2017).

Presenter: Nguyen Ngoc Anh