AMS检测铅中超重核~(298)Fl
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摘要
理论物理学家根据壳模型预言自然界存在超重稳定岛,然而迄今为止没有找到。本文利用加速器质谱(AMS)开展高灵敏的超重核~(298)Fl的测量方法研究,其中主要包括测量样品的选择、离子源引出形式的确定、超重核的传输与测量和测量系统稳定性的监测。超重核~(298)Fl的每种样品测量计数均为0。理论计算结果表明,在所测的铅样品中,超重核~(298)Fl与Pb的原子个数比值上限约为10-12~10-14。
Theoretical physicists predict that there is an island of stability in nature according to the nuclear shell model,but so far there is no evidence for the existence of super-heavy nuclei. In the paper,a highly sensitive measurement method for super-heavy nuclei ~(298)Fl with accelerator mass spectrometry( AMS) was developed,which mainly included the selection of experimental samples,the determination of ionic extraction form,the transmission and measurement of super-heavy nuclei and the monitoring of the system stability. The count is zero for each measurement of super-heavy nuclei~(298)Fl. The theoretical calculation result indicates that the upper limit of the number ratio of super-heavy nuclei~(298)Fl and Pb in lead samples is on the order of 10~(-12)-10~(-14).
Theoretical physicists predict that there is an island of stability in nature according to the nuclear shell model,but so far there is no evidence for the existence of super-heavy nuclei. In the paper,a highly sensitive measurement method for super-heavy nuclei ~(298)Fl with accelerator mass spectrometry( AMS) was developed,which mainly included the selection of experimental samples,the determination of ionic extraction form,the transmission and measurement of super-heavy nuclei and the monitoring of the system stability. The count is zero for each measurement of super-heavy nuclei~(298)Fl. The theoretical calculation result indicates that the upper limit of the number ratio of super-heavy nuclei~(298)Fl and Pb in lead samples is on the order of 10~(-12)-10~(-14).
引文
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[2]SOBICZEWSKI A,GAREEV F,KALINKIN B.Closed shells for Z>82 and N>126 in a diffuse potential well[J].Physics Letters,1966,22(4):500-502.
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[4]MOSEL U,GREINER W.On the stability of superheavy nuclei against fission[J].Zeitschrift für Physik,1969,222(3):643-652.
[5]MOLLER P,NIX J R.Stability of heavy and superheavy elements[J].Journal of Physics G:Nuclear and Particle Physics,1994,20(11):1 681-1747.
[6]C'WIOK S,DOBACZEWSKI J,HEENEN P H,et al.Shell structure of the superheavy elements[J].Nuclear Physics A,1996,611(2):211-246.
[7]RUTZ K,BENDER M,BRVENICH T,et al.Superheavy nuclei in self-consistent nuclear calculations[J].Physical Review C,1997,56(1):211-246.
[8]PATRA S K,WU Chengli,PRAHARAJ C R,et al.A systematic study of superheavy nuclei for Z=114 and beyond using the relativistic mean field approach[J].Nuclear Physics A,1999,651(2):117-139.
[9]KRUPPA A T,BENDER M,NAZAREWICZ W,et al.Shell corrections of superheavy nuclei in selfconsistent calculations[J].Physical Review C,2000,61(3):034313.
[10]SCHRAMM D N,FOWLER W A.Synthesis of superheavy elements in the r-process[J].Nature,1971,231:103-106.
[11]BRUECKNER K A,CHIRICO J H,JORNA S,et al.Superheavy elements from r-process calculations with an energy-density mass formula[J].Physical Review C,1973,7(5):2 123-2 128.
[12]OGANESSIAN Y T,UTYONKOV V K,LOBANOV Y V,et al.Synthesis of the isotopes of elements118 and 116 in the249Cf and245Cm+48Ca fusion reactions[J].Physical Review C,2006,74(4):044602.
[13]CHEIFETZ E,JARED R C,GIUSTI E R,et al.Search for superheavy elements in nature[J].Physical Review C,1972,6(4):1 348-1 361.
[14]DONADILLE L,LIATARD E,BENOIT B,et al.Fission dynamics for capture reactions in58,64Ni+208Pb systems:New results in terms of thermal energy and neutron multiplicity correlated distributions[J].Nuclear Physics A,1999,656(2):259-283.
[15]MARINOV A,RODUSHKIN I,KOLB D,et al.Evidence for the possible existence of a long-lived superheavy nucleus with atomic mass number A=292 and atomic number Z122 in natural Th[J].International Journal of Modern Physics E,2010,19(1):131-140.
[16]MARINOV A,PAPE A,KOLB D,et al.Enrichment of the superheavy element roentgenium(Rg)in natural Au[J].International Journal of Modern Physics E,2011,20(11):2 391-2 401.
[17]LACHNER J,DILLMANN I,FAESTERMANN T,et al.Search for long-lived isomeric states in neutron-deficient thorium isotopes[J].Physical Review C,2008,78(6):064313.
[18]DELLINGER F,KUTSCHERA W,FORSTNER O,et al.Upper limits for the existence of long-lived isotopes of roentgenium in natural gold[J].Physical Review C,2011,83(1):015801.
[19]DELLINGER F,FORSTNER O,GOLSER R,et al.Ultrasensitive search for long-lived superheavy nuclides in the mass range A=288 to A=300 in natural Pt,Pb,and Bi[J].Physical Review C,2011,83(6):065806.
[20]LUDWIG P,FAESTERMANN T,KORSCHINEK G,et al.Search for superheavy elements with 292≤A≤310 in nature with accelerator mass spectrometry[J].Physical Review C,2012,85(2):024315.
[21]SETH M,FAEGRI K,SCHWERDTFEGER P.The stability of the oxidation state+4 in group 14 compounds from carbon to element 114[J].Angewandte Chemie International Edition,1998,37(18):2 493-2 496.
[22]GIJU K T,de PROFT F,GEERLINGS P.Comprehensive study of density functional theory based properties for group 14 atoms and functional groups,-XY3(X=C,Si,Ge,Sn,Pb,element 114;Y=CH3,H,F,Cl,Br,I,At)[J].The Journal of Physical Chemistry A,2005,109(12):2 925-2936.