超重核 ( 新元素 ) 研究进展 任中洲 南京大学 物理学院

超重核 ( 新元素 ) 研究进展 任中洲

南京大学 物理学院南京大学 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

R. Eichler et al, NATURE, Vol.447(2007)72, Chemical characterization of element 112Oganessian et al., Phys. Rev. Lett. 104, 142502 (2010) Synthesis of a New Element with Atomic Number Z=117

R. Eichler et al, NATURE, Vol.447(2007)72, Chemical characterization of element 112Oganessian et al., Phys. Rev. Lett. 104, 142502 (2010) Synthesis of a New Element with Atomic Number Z=117

Cn112

Cn112

117117

超重元素研究现状 (Z=112, Cn)

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

nucleiProton 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？？？

超 重 新 核 素 259Db (Z=105),265Bh (Z=107)

中科院近代物理研究所

259Db0. 5 s

9.47

265Bh0.94 s

9.24

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).

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

Table 1, RMF results for Cf. (TMA and NLZ2)

Experimental deformation Beta2=0.30 for 250,252Cf

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

Table 2, RMF results for No. (TMA and NLZ2)

Experimental deformation Beta2=0.27 for 254No

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.

Nuclei Bthe. Beta

n

Betap Qthe. Qexp.

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

Tab. 4, results for GSI data 269110. (TMA)

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)

• 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-Livemore-

PSI)• 论文被综述文章引用 (Nature, PRC, JPG)

南京大学

Predictions of SHF and RMF compare well with MM results [12,13]

Oganessian et al, PRC72 2005

南京大学

SHF [12 ， 49-51] and RMF [13 ， 52-57] compare well with the experimental results

Oganessian et al, PRC72 2005

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

(MeV)

Ta

(second)269109 1960.17 0.22 0.23 10.21 0.069265107 1942.08 0.23 0.24 9.41 2.56261105 1923.19 0.26 0.26 9.14 3.33257103 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

• 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

• 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

The Reid nucleon-nucleon potential

Nuclear Matter : G-MatrixM3Y

Bertsch et al.

Satchler et al.

Alpha ScatteringRM3Y

1/30DDCMElectron Scattering

Nuclear MatterAlpha Clustering (1/3)

Alpha Clustering

Brink et al.

1987PRL

Tonozuka et al.

Hofstadter et al.

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)

[46] C. Xu, Z. Ren, Phys. Rev. C 75 (2007) 044301

论文被引用：理论核形变与新实验结果一致

国外同行引用举例 ( 三 )

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

Zhang et al.,PRC80 2009

This is in agreement with Ref. [40].这与文献 [40] 一致

原子能院和北航工作（二） : 五篇被引

Heavy and superheavy nucleiNPA 825 145-158 (2009)

V0 is determined by the characteristic of the alpha-cluster quasibound state.

Woods-Saxon shape nuclear potentials

Solve S-eq. for quasi-bound 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, Bohr-Sommerfeld 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.

V0 is determined by the characteristic of the alpha-cluster quasibound state.

Woods-Saxon shape nuclear potentials

Woods-Saxon 势球形核准束缚态波函数

Behaving like the irregular Coulombwave function

The number of internal nodes is determined by the Wildermuth condition

4

1

2 ii

G n L g

( )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.

2 2

, 02 2

( 1)( ) ( ) ( ) ( )

2 d

I II I J J J I

J

du r V r u r Q E u r

dr r

0+

2+

4+

6+

Exp. Cal.

248Cf0+

80.00% 79.22%

19.60% 19.98%

0.40% 0.79%

0.0046%---

T1/2(s) 2.88*107 2.43*107

0+

2+

4+

6+

Exp. Cal.

248Cf0+

80.00% 79.22%

19.60% 19.98%

0.40% 0.79%

0.0046%---

T1/2(s) 2.88*107 2.43*107

0+

2+

4+

6+

Exp. Cal.

250Cf0+

84.70% 80.74%

15.00% 18.56%

0.30% 0.70%

0.0039%0.010%

T1/2(s) 4.13*108 3.29*108

Calculated results for two isotopes of Cf

0+

2+

4+

6+

Exp. Cal.

252Fm0+

84.00% 79.22%

15.00% 19.62%

0.97% 1.15%

0.014%0.023%

T1/2(s) 9.14*104 4.82*104

0+

2+

4+

6+

Exp. Cal.

254Fm0+

85.00% 81.09%

14.20% 17.81%

0.82% 1.08%

0.013%0.0066%

T1/2(s) 1.17*104 1.01*104

Calculated results for two isotopes of Fm

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 half-lives 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 (GSI; Dubna) ??? Z=109, Meitnerium. (GSI) Z=110, Darmstadium…. (GSI)