Chinese Physics C > 2001, Vol. 25 > Issue(8): 725-730

Level Structure in²⁰⁹Fr

Institute of Modern Physics,The Chinese Academy of Sciences,Lanzhou 730000,China

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Abstract：
The high-spin states of ²⁰⁹Fr have been studied in the ¹⁹⁷Au( ¹⁶O,4n) ²⁰⁹Fr reaction at ¹⁶O energies from 90 to 105 MeV using techniques of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation functions,γ-γ-t coincidences and γ-ray angular distributions were performed with 4 BGO(AC)HPGe detecters. A level scheme for ²⁰⁹Fr with 21 γ rays was established for the first time,including a high-spin isomer with a measured half-life of (52±20)ns. Comparing with the low-lying level structure in ²⁰⁸Rn,it may conclude that the low-lying levels in ²⁰⁹Fr are formed by coupling the h _9/2proton to the neutron hole excitations in ²⁰⁸Rn. Thus,negative parities could be assigned tentatively to the low-lying states. The nucleus ²⁰⁹Fr,with four valence neutron holes and five valence protons outside the closed-shell nucleus ²⁰⁸Pb,also presents a competition between neutron-hole excitations and proton excitations in its low-lying level spectrum. Additionally,it should be pointed out that the higher-lying level structure in ²⁰⁹Fr does not follow the excitation pattern of ²⁰⁸Rn. We will pursue shell model calculations to interpret the level structure in ²⁰⁹Fr.

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[1]

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ZHOU Xiao-Hong, GUO Ying-Xiang, ZHU Shao-Fei, LEI Xiang-Guo, LIU Min-Liang, LIU Zhong, ZHANG Yu-Hu, HE Jian-Jun, ZHENG Yong and LUO Yi-Xiao. Level Structure in ²⁰⁹Fr[J]. Chinese Physics C, 2001, 25(8): 725-730.

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Received: 2000-09-07
Revised: 1900-01-01

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通讯作者:陈斌, bchen63@163.com

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沈阳化工大学材料科学与工程学院沈阳 110142

Level Structure in²⁰⁹Fr

Corresponding author:ZHOU Xiao-Hong,

Institute of Modern Physics,The Chinese Academy of Sciences,Lanzhou 730000,China

Received Date:2000-09-07

Accepted Date:1900-01-01

Available Online:2001-08-05

Abstract:The high-spin states of²⁰⁹Fr have been studied in the¹⁹⁷Au(¹⁶O,4n)²⁰⁹Fr reaction at¹⁶O energies from 90 to 105 MeV using techniques of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation functions,γ-γ-t coincidences and γ-ray angular distributions were performed with 4 BGO(AC)HPGe detecters. A level scheme for²⁰⁹Fr with 21 γ rays was established for the first time,including a high-spin isomer with a measured half-life of (52±20)ns. Comparing with the low-lying level structure in²⁰⁸Rn,it may conclude that the low-lying levels in²⁰⁹Fr are formed by coupling the h_9/2proton to the neutron hole excitations in²⁰⁸Rn. Thus,negative parities could be assigned tentatively to the low-lying states. The nucleus²⁰⁹Fr,with four valence neutron holes and five valence protons outside the closed-shell nucleus²⁰⁸Pb,also presents a competition between neutron-hole excitations and proton excitations in its low-lying level spectrum. Additionally,it should be pointed out that the higher-lying level structure in²⁰⁹Fr does not follow the excitation pattern of²⁰⁸Rn. We will pursue shell model calculations to interpret the level structure in²⁰⁹Fr.

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Level Structure in²⁰⁹Fr

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通讯作者:陈斌, bchen63@163.com

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