Transcript 超重核(新元素)

超重核(新元素)研究进展
任中洲
南京大学 物理学院
• 寻找重元素的历史回顾
• 实验的新进展
• 理论研究状况
• Z=118新元素的合成(Dubna)
周期表 (1869): 门捷列夫未获 Nobel Prize
周期表
(2000)
WebElements: the periodic table
化学元素周期表2008
超重元素研究现状 (Z=112, Cn)
C
n
117
112
R. Eichler et al, NATURE, Vol.447(2007)72, Chemical characterization of element 112
Oganessian et al., Phys. Rev. Lett. 104, 142502 (2010)
Synthesis of a New Element with Atomic Number Z=117
近年来研究超重原子核(新元素) 的性质是国
际核物理的热点之一.
核素图
1 寻找重元素的历史
• 早期物理学家寻找新化学元素
• 物理学+化学:
• 光谱线: Fraunhofer, Kirchhoff +Bunsen
(Germany): Cs, Rb (37,55); Crookes,
Tl(81).
• 物理学+天文学:
• 日蚀时，观察新光谱线 ，太阳元素：氦
法国物理学家，英国天文学家（1868）.
为什么物理学家介入：物理方法威力大。
1903-1904: Nobel Prize and new
elements
• 1. Rayleigh (physicist: N) +Ramsy (chemist):
•
•
•
•
•
Ar; He (Crookes: confirm), Ne ,Kr
1904 Nobel prize ( Physics+Chemistry)
2. M. Curie and P. Curie: Radioactivity;
Stronger : new elements, Ra, Po (1898) ?
1903 Nobel prize (Physics) 1/2+(1/4+1/4)
1911 Nobel prize (Chemistry)
M. Curie, when she got the first Nobel prize
Brief Introduction : (g.s.)
Important decay modes of nuclei
Proton emission (Z >51)
Alpha decay (Z>=52)
Cluster radioactivity (Z >=87)
Spontaneous fission (Z >= 90)
References on arguments
• 1. A history of physics, Dover
Publications, F. Cajori , 1962, USA.
• 2. Une Femme Honorable, Marie Curie;
• De Francoise Giroud;
• Librairie Artheme Fatard, 1981.
• 3. A short history of nearly everything,
• Bill Bryson, Jed Mattes Inc. , 2003
Lord Kelvin
学术争论双刃剑
• M. Curie won the Nobel Prize of
Chemistry in 1911. newspaper ?
• Boltzman, argument on the existence of
atoms…
• Ehrenfeste ? Quantum mechanics.…
1 寻找新元素的历史
• 周期表中30多个元素由核方法合成
• 1930—1949 找到“失踪”元素
• 重元素 （U 以后：Z=93,94?)合成
• 核合成的元素被化学家证实
为什么核合成？ 稀有 或 放射性。
Year of discovery (1896-1996)
重元素合成的意义 （1）
• 扩展元素周期表
• 到底有多少个化学元素 ？
• 新元素的应用？超重岛存在？
• 超重岛存在机制？ 新现象？
元素的合成和命名
Z=101, Mendelevium
(Berkeley).
Z=102, Nobelium
(Berkeley +Nobel)
Z=103, Lawrencium.
(Berkeley)
Z=104, Rutherfordium.
(Berkeley;Dubna ?)
Z=105, Db, Dubnium
(Dubna;Berkeley ?)
Z=106, Seaborgium.
(Dubna;Berkeley !)
Z=107, Bohrium
(Dubna)
Z=108, Hassium
(GSI; Dubna ?!)
Z=109, Meitnerium.
(GSI)
Z=110, Ds, Darmstadium
Z=111, Rg, Roentgenium
Z=112, Cn, Copernicium
(GSI)
New elements Z=114 and Z=116 (Dubna)
Z=114, nature
2. Summary of New Results
• The elements Z=110,111,112 were produced at
GSI, Hofmann, Muenzenberg…. Z. Phys. A, 1995, 1996.
• Z=114 was synthesized at Dubna by Oganessian et al.
Nature, 1999; Phys. Rev. Lett. 1999;Phys. Rev. C, 2000.
• Z=116 , Z=115, Z=118 were produced at Dubna in 2000s.
Oganessian et al, Phys. Rev. C, 2001-2006. Z=117, 2010
• Z=113, RIKEN; PSI: 270 108; GSI: 270110 ; Lanzhou:
265107…. 继续争论？？？ 新元素？？？
265Bh
0.94 s
9.24
a
259Db
0. 5 s
9.47 a
超 重 新 核 素 259Db
(Z=105),265Bh (Z=107)
中科院近代物理研究所
国内超重新核素实验265Bh (Z=107)
265Bh的实验结果与理论预言一致
最新超重核评述文章：Oganessian JPG 2007
3. theory.
• J. A. Wheeler et al, 1950s: Superheavy nuclei
• P.R., 1958.
• Bethe and his collaborator, PRL, 1967.
• 1960s-1980s, macroscopic-microscopic model
(MM): Nilsson et al, Z=114 and N=184 ?
• Moeller, Nix, Kratz, At. Dat. Nu. Dat. 1997.
• Myers and Swiatecki, PRC, 1998.
Werner and Wheeler, PR, 1958:
superheavy nuclei
Siemens and Bethe: nuclei with Z>104 are prolate
3. Theory ( SHF and RMF 1990--)
• Zhongzhou REN et al, JPG, 1996; CPL, 1997.
• Lalazissis, Ring et al, NPA, 1996.
• Cwiok, Nazarewicz, Heenen, PRL, 1999.
• Ren and Toki, Nucl. Phys. A689 (2001) 691:
Z=110-112,114. Ren, PRC, 2002,May,(R);PRC,
Dec.,2002
• Ren et al, PRC 2003, PRC2004, PRC2005...
Relativistic mean-field model
• Protons and neutrons interact by exchanges of
mesons (strong interactions)
• There is the electromagnetic interactions
among protons by exchange of photons
• Atomic nucleus is a many-body system
• Solve the coupled Dirac equations
• and the Klein-Gordon equations
3. Numerical results and
discussion
• Z: 94—116; N:150—184. Test the model for
even-even nuclei:
• Comparison of RMF model and Moeller
result for the alpha chain of 277112.
* Theoretical decay energy for Z=110-112.
Theoretical decay energy for Z=114, 116.
Nuclear structure : Shape coexistence in
superheavy nuclei
Fig. 3 Theoretical and experimental alpha decay energies
for GSI Data: Z=110, 111, 112 ( +2, +1, 0 shift).
Table 1, RMF results for Cf. (TMA and NLZ2)
Nuclei
Bthe. (1)
Betap Bthe.(2)
Betap
Bexp.(MeV)
244Cf
1832.9
0.26
1829.7
0.31
1831.3
246Cf
1846.3
0.27
1843.1
0.31
1844.8
248Cf
1859.0
0.26
1855.5
0.31
1857.8
250Cf
1871.0
0.26
1866.9
0.31
1870.0
252Cf
1882.4
0.26
1877.8
0.31
1881.3
254Cf
1892.9
0.25
1888.5
0.30
1892.1
Experimental deformation Beta2=0.30 for 250,252Cf
Table 2, RMF results for No. (TMA and NLZ2)
Nuclei
Bthe. (1)
Betap Bthe.(2)
Betap
Bexp.(MeV)
252No
1873.2
0.26
1870.7
0.31
1871.3
254No
1887.2
0.27
1884.1
0.31
1885.6
256No
1900.7
0.27
1897.0
0.31
1898.6
258No
1912.9
0.27
1909.6
0.30
1911.1audi
260No
1924.6
0.26
1921.7
0.30
1923.1audi
262No
1935.8
0.21
1933.1
0.29
1934.7audi
Fig. 1 Energy surface of Z=108, A=264
Experimental B/A (MeV) is between
two sets of RMF results (Z=98-108).
Fig. 2 Binding energy of the Z=112, A=277 chain
from the RMF and Moller et al.
Tab. 4, results for GSI data 269110. (TMA)
Nuclei
Bthe.
Beta Betap
Qthe.
Qexp.
n
269110
1954.4 0.22
0.23
11.56
11.13
265108
1937.7 0.24
0.25
9.92
10.57
261106
1919.3 0.25
0.26
9.17
9.58
257104
1900.1 0.26
0.26
8.61
8.71
253102
1880.5 0.26
0.27
8.25
8.14
Fig. 4 Theoretical and experimental alpha decay energy
for Z=114, A=289 and Z=118, A=293
创新点及意义 (1)
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•
提出超重核形状共存----可能是超重核存在新机制:
改进和发展了数值计算方法和程序
完成大规模数值计算
提出超重核形状共存, 形变重要, 有低能同质异能态
• 发表了一系列论文(PRC 3篇; NPA 2篇等)
• 论文被国外同行引用和肯定:
• 论文被国际上著名实验小组引用(Dubna-LivemorePSI)
• 论文被综述文章引用(Nature, PRC, JPG)
Oganessian et al,
PRC72 2005
Predictions of SHF and RMF
compare well with MM results
[12,13]
南京大学
Oganessian et al, PRC72 2005
SHF [12，49-51] and RMF
[13，52-57] compare well
with the experimental
results
南京大学
15. Ren, Z. Shape coexistence in even-even
superheavy nuclei. Phys. Rev. C65, 051304 (2002)
Cited: shape coexistence, Ref. [15]
Nature, 433 (2005) 705
64. Z. Ren, Phys. Rev. C65, (2002) 051304(R)
65. Z. Ren et al., Phys. Rev. C66, (2002) 064306
Exp. Def. : 0.28, RMF Def.: 0.26-0.32,cited.
…Z. Qin, 形变双幻核270Hs：理论预言与实验一致
Sharma,… Stevenson, Gupta, Greiner agree with us:
shape coexistence and superdeformation
Geng, Toki, Zhao: similar results with us.
Geng, Toki, Zhao JPG 32 (2006) 573:
shape coexistence and superdeformation.
Other RMF calculations agree with ours:
superdeformation in superheavy nuclei
配合国内实验, 理论预言: 265107 Qa and Ta
Z. Ren et al, PRC 67 (2003) 064302;
JNRS 3 (2002) 195.
AX
B
(MeV)
Betan
Betap
Qa
Ta
(MeV) (second)
269109
1960.17
0.22
0.23
10.21
0.069
265107
1942.08
0.23
0.24
9.41
2.56
261105
1923.19
0.26
0.26
9.14
3.33
257103
1904.03
0.26
0.27
8.12
1.28*103
Expt: Gan et al, EPJA 2004, Qa=9.38 , Ta=0.94 s.
Good agreement between theory and data.
国内超重新核素实验265Bh (Z=107)
265Bh的实验结果与理论预言一致
3. Density-Dependent Cluster Model
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DDCM is a new model of alpha and cluster decay:
1) effectve potential based on the Reid potential.
2) low density behavior included.
3) exchange included
4) agreement within a factor of three for half-lives
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•
Z Ren, C Xu, Z Wang, PRC 70: 034304 (2004)
C Xu, Z Ren, NPA 753: 174 (2005)
C Xu, Z Ren, NPA 760: 303 (2005)
C. Xu, Z. Ren, PRC 73: 041301(R) (2006)…
DDCM for superheavy nuclei (Z=106-118)
Density-Dependent Cluster Model
• 建立了球形和形变核双折叠势程序
• 推导了球形，形变核alpha衰变寿命公式
• 对已知alpha衰变寿命进行了大规模计算
• 对结团放射性进行了系统研究
Density-dependent cluster model of alpha decay
Bertsch et al.
The Reid
nucleon-nucleon potential
Nuclear Matter : G-Matrix
M3Y
Satchler et al.
Hofstadter et al.
Electron Scattering
DDCM
Brink et al.
Nuclear Matter
Alpha Clustering (1/3)
1/30
Alpha Scattering
RM3Y
Tonozuka et al.
1987PRL
Alpha Clustering
Deformed DDCM: a spherical alpha-particle interacts
with a deformed daughter nucleus with an axially
symmetric deformation
The distribution of the number of alpha emitters
for different factors of agreement (Even-Even).
The comparison of experimental alpha-decay half-lives
and theoretical ones for even-even nuclei (Z= 52−104)
国外同行引用举例 (三)
论文被引用：理论核形变与新实验结果一致
[46] C. Xu, Z. Ren, Phys. Rev. C 75 (2007) 044301
国外同行引用举例 (四):PRC2010
Ismail follows Refs. [8-9].
多处引用我们工作[8-9].
国外引用 (四): follow us
国外引用 (四)：follow us,全文13处引用
They use more recent values that were
proposed in Ref. [60].
北大和理论所的工作举例
该文引用了我们的工作: 见下页
国内同行引用举例（一）
从折叠模型获得的微观势被成功地应用到alpha衰变和
alpha散射的计算中 [9-12]
国内同行引用举例（一）
文献[39,40]指出形变可以影响alpha衰变的寿命
原子能院和北航工作（二）: 五篇被引
Zhang et al.,
PRC80 2009
This is in agreement
with Ref. [40].
这与文献 [40] 一致
Heavy and superheavy nuclei
NPA 825 145-158 (2009)
Solve S-eq. for quasi-bound state
Woods-Saxon shape
nuclear potentials
V0 is determined by the
characteristic of the alphacluster quasibound state.
Generalized DDCM : 系列工作, 量子
PRC 80 014314 (2009)……
我们小组alpha衰变寿命工作(2009-2010)
• 2009-2010建立推广的密度依赖结团模型GDDCM,
解准束缚态薛定谔方程，纯量子模型：
Ni and Ren NPA 825, 145 (2009); 828, 348 (2009);
PRC 80, 014314 (2009); 80, 051303(R) (2009); 81,
024315 (2010).
• 2010建立计算形变核alpha衰变寿命和分支比的新
模型—多道结团模型(MCCM)，第一次完成四道耦
合自洽计算:
Ni and Ren PRC 81, 064318 (2010)....
准束缚态问题来源
• 量子力学源于原子物理：束缚态，散射态（教科书）
• 1928，Gomov用量子力学定性解释原子核α衰变
• 不稳定原子核的特点：有限寿命—准束缚态（Q-BS）
• 已有理论模型：半经典或准经典近似（WKB, BohrSommerfeld quantization）
• α衰变是一个纯量子效应，应解准束缚态薛定谔方程
• GDDCM is a new version of DDCM:
• 1) pure quantum version of decay
• 2) wave functions are obtained by S-eq. for Q-BS.
Woods-Saxon势球形核准束缚态波函数
Woods-Saxon shape
nuclear potentials
V0 is determined by the
characteristic of the alphacluster quasibound state.
The number of internal nodes is determined
by the Wildermuth condition
4
G  2n  L   g i
i 1
Behaving like the irregular Coulomb
wave function G (r )
新版本密度依赖结团模型：PRC 80 (2009) 051303(R)
微观计算形变核alpha衰变寿命
形变核alpha衰变新模型：多道结团模型(MCCM)
多道结团模型(MCCM): 准束缚态耦合S-eq.
0+
248Cf
Exp.
---
Cal.
0.0046% +
6
0.40% 0.79% +
4
19.60% 19.98% +
2
80.00% 79.22%
0+
T1/2(s) 2.88*107 2.43*107
 d2



2
2  dr
2
I
(
 1) 
uI (r )  VI , J (r )uJ (r )  Q0  EJd uI (r )

r
J

I
2


Calculated results for two isotopes of Cf
0+
0+
248Cf
Exp.
250Cf
Exp.
Cal.
Cal.
0.0046%
6+
0.40% 0.79%
4+
19.60% 19.98%
2+
0.010% 0.0039%
80.00% 79.22%
84.70% 80.74%
---
0+
T1/2(s) 2.88*107 2.43*107
0.30%
0.70%
6+
4+
15.00% 18.56%
2+
0+
T1/2(s) 4.13*108 3.29*108
Calculated results for two isotopes of Fm
0+
0+
252Fm
Exp.
Cal.
0.023% 0.014%
0.97%
1.15%
254Fm
Exp.
6+
4+
15.00% 19.62%
2+
84.00% 79.22%
0+
T1/2(s) 9.14*104 4.82*104
Cal.
0.0066% 0.013%
0.82%
1.08%
6+
4+
14.20% 17.81%
2+
85.00% 81.09%
0+
T1/2(s) 1.17*104 1.01*104
Synthesis of new element Z=118
1. 2002, Dubna: D7-2002-287
2. PRC69, 2004 (May).
3. PRC70, 2004 (Dec.).
4. Phys. Scrt. 2006 (June)
5. PRC 74, 2006 (October).
Oganessian PRC69 (2004): Z=118
Oganessian PRC69 (2004): Z=118
Oganessian PRC74 (2006): Z=118
APS: Physics News Update October
Xu and Ren, PRC 69 (2004) (Feb.)
Various shapes of superheavy nuclei
• Old picture: Spherical. Z=114 and N=184.
• Prof. Greiner: Fullerene (Buckyball, 60C).
(sixty alpha particles for Z=120 )
• Our idea: American football . (Isomers)
( shape coexistence or superdeformation).
• Which shape do you prefer ?
Superheavy nuclei: American
football; round ball; Soccer (60C)
新元素 Z=122 ? (2008. 04)
To produce Z=117 element in
China?
• We estimate the alpha-decay energies and halflives of Z=117 elements.
• We will estimate the spontaneous
fission half-lives of Z=117 element.
The goal of 973 of Nuclear Physics: 2007-2012
Synthesis of the 117th element, PRL
遗憾; 我们2003提出, 希望国内完成
• 俄国人和美国人捷足先登
• 我们判断正确 Z=117
• 国内实验落后
3. Summary (1)
• The properties of even-even nuclei with Z=94—
116 are investigated in the RMF model.
• The constraint RMF calculation shows clearly
the coexistence of shape in superheavy nuclei.
This is useful for a deeper binding and may be
a new mechanism of appearance of superheavy
islands.
3. Summary (2)
• We propose new models of alpha decay:
• Density-dependent cluster model (DDCM)
• Multi-channel cluster model (MCCM).
• Agree well with known data.
• Good prediction for unknown half-lives.
•
谢 谢！
THANKS!
元素的命名
Z=101, Md, Mendelevium. (Berkeley).
Z=102, No. Nobelium
(Berkeley +Nobel)
Z=103, Lr, Lawrencium.
(Berkeley)
Z=104, Rutherfordium.
(Berkeley;Dubna) ?
Z=105, Db, Dubnium
(Dubna;Berkeley) ?
Z=106, Seaborgium.
(Dubna;Berkeley) ?
Z=107, Bohrium
(Dubna)
Z=108, Hassium
Z=109, Meitnerium.
Z=110, Darmstadium….
(GSI; Dubna) ???
(GSI)
(GSI)