Amnon Marinov

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Prof. Amnon Marinov

Amnon Marinov (1930 – 7 December 2011) was born in Jerusalem in 1930 to parents who emigrated from Russia in the 1920s. In 1948 he joined the Palmach and fought in the Israeli War of Independence. When the war was over he became one of the founders of Kibbutz Tzor'a in the Judea Mountains. While still a kibbutz member he began his physics studies in the Hebrew University of Jerusalem. In 1957 he moved to Jerusalem and continued his studies, specializing in nuclear physics. He completed his doctoral dissertation on the Mossbauer Effect in 1963, and spent his post-doctorate in the Argonne National Laboratories, Illinois, USA.

Work[edit]

Marinov's interest in super-heavy elements (SHE) began in 1971 while he was a research associate at Rutherford High Energy Laboratories, Berkshire, England. Already in the nineteen sixties quite a few theoretical calculations predicted the existence of an Island of Stability around Z=114 and N=184, which were supposed to be the next proton and neutron closed shells. Some of these calculations predicted very long lifetimes for some isotopes in this region of up to a half-life of 109 years.[1]

These predictions excited the nuclear physics community, triggering three parallel paths of research: 1) Some scientists started to build their heavy ion accelerators in GSI, Berkeley, Dubna (Russia) and recently in Riken (Japan); 2) Others began searching for the existence of super-heavy elements in various natural materials. The results of most of these searches were negative, but some unexplained phenomena, which will be discussed later on, were observed; 3) Marinov's approach was to try to produce super-heavy elements by Secondary Reaction Experiments.

By creating secondary reactions that were produced in a Tungsten target bombarded by 24 GeV protons, he and his associates discovered evidence for the existence of a super-heavy element with atomic number 112 (Copernicium), atomic mass 272, homologous to Mercury and having a half-life of 47 days.[2] In 1984, basing their arguments on mass separator measurements, they concluded that the previously formed nuclei are a neutron-deficient super-heavy element with Z=112 and approximately 160 neutrons.[3]

Some problems were encountered regarding the theoretically predicted versus the empirically discovered properties of these super-heavy elements. One problem was that the deduced cross-section of these super-heavy elements was approximately 4 mb, whereas their typical measured cross-sections was about 1 pb, thus creating a difference of 9 orders of magnitude.
It has already been shown that deformations have strong effect on the fusion cross-sections;[4] this can explain 4 to 5 orders of magnitude, leaving about 4-5 orders of magnitude in the fusion cross-section to be explained. The answer was found by studying actinides that were separated from the Tungsten target. In the actinide spectra other α particle groups were observed that were impossible to identify with any known activity in the whole nuclear chart and did not fit with the systematic of α - particles; their energies were too low, and they passed the Coulomb barrier too fast. By using a pelletron accelerator and measuring α – γ coincidences from the catcher foil, Marinov and his group found 5.2 MeV α - particle group in coincidence with various γ - rays of σ ≈ 30 nb, which was identified as a transition from 210Fr to 206At; and the reason that it decayed with low energy when much higher energy was available was that it was enhanced by a factor of 3x105. This explained the remaining 5 orders of magnitude, with the conclusion that the 5.2 MeV α – particles decay to a superdeformed band state.[5]
In the 1990s Marinov began to search for the existence of super-heavy elements in nature. The assumed existence of long-lived isomeric states has already led to a consistent interpretation of results in the super-heavy region.[6] These isomeric states were observed in Americium and Berkelium nuclei sources separated from a CERN Tungsten target, and were interpreted due to the production of long-lived isomeric states in neutron-deficient 236Am and 236Bk which decay to 236Pu.[7]
In order to measure the accurate mass of an atom, a high-resolution mass spectrometer, based on the principle that the mass of any molecule (except for multi-hydrogen molecules) is lower than the mass of an atom with the same mass number, was used in order to separate between the mass of an atom and the masses of molecules of the same mass number was used. Measuring neutron-deficient nuclei from a pure Thorium solution, Marinov discovered that the relative abundance of various Thorium isotopes (211, 213, 217, 218) compared to 232Th is (1 -10)x10−11.
If the terrestrial concentration of these isotopes was initially the same as of 232Th, then their half-lives would be >= 108 years. Marinov concluded therefore that long-lived isomeric states with half-lives 1016 to 1022 longer than their corresponding ground states have been found in the neutron-deficient 211,213,217,218Th nuclei.[8]
Long-lived isomeric states were also observed in 16O + 197Au reaction at 80 MeV.[9] In this experiment Marinov searched for long-lived isomeric states in pure Gold solution looking for high masses, assuming that if Roentgenium (eka-Gold, element 111) exists in nature it may be found together with Gold. The relative abundance of isotopes 261Rg and 265Rg compared to 197Au was found to be (1-10)x10−10. He therefore assumed that the observed nuclei of atomic mass number A=261 and 265 nuclei were respectively 261Rg and 265Rg (element 111) respectively.[10]
Marinov's third experiment consisted of searching for super-heavy elements in Thorium solution at high masses from 287 to 294, looking for super-actinide nuclei. According to Seaborg's extended periodic table of elements, elements 122 and 124 are placed as eka-Thorium and eka-Uranium respectively. It was discovered that nuclei of atomic mass A=292 are in abundance of (1-10)x10−12 (relative to 232Th), and have a half-life which is >= 108 years. Since the predicted half-lives of nuclei around 292122 is 10−6 to 10−8 seconds, and the empirically measured half-lives of these nuclei is >= 108 years, Marinov concluded that this was an isomeric state in the nucleus of atomic mass A=292 and atomic number Z~=122.
Thus, the discovery of long-lived high spin isomeric states in the second minimum (the super-deformed minimum) and in the third minimum (the hyper-deformed minimum) of the potential energy of nuclei when displayed as a function of deformation[disambiguation needed], and the fact that these isomeric states have unusual radioactive decay properties and much longer lifetimes than their corresponding ground states, have led Marinov to his recent discovery of evidence for a long-lived super-heavy nucleus with atomic mass number A=292 and atomic number Z~=122 in natural Thorium.[11]

Family[edit]

Amnon Marinov lived in Jerusalem, Israel with his wife Rachel, and they have four children and six grandchildren. His father, Haim Marinov (1904–2001), was the deputy-mayor of Jerusalem from 1964 until 1973. His father-in-law, Ya'akov Maimon (1902–1977), was the inventor of Hebrew stenography and received the Israel Prize in 1976 for his lifelong voluntary work teaching Hebrew to new immigrants all over the country. Amnon Marinov died on December 7, 2011.

References[edit]

  1. ^ These are some of the pioneering works:
    • V. M. Strutinskii, Yadernaya fizika 3, 614 (1964).
    • W. Myers and W. Swiateski, Nucl. Phys. 81, 1 (1966).
    • A. Sobiczewski, F. A. Gareev and B. N. Kalinkin, Phys. Lett. 22,590 (1966).
    • V. M. Strutinskii, Nucl. Phys. A95, 420 (1967).
    • C. L. Wong, Phys. Rev. Lett. 19, 328 (1967).
    • Yu. A. Muzychka, V. V. Pashkevich and Strutinskii, Dubna Preprint R7-3733, 1968.
    • S. G. Nilsson, J. R. Nix, A. Sobiczewski, Z. Szymanski, S. Wycech, C. Gustafson and P. Möller, Nucl. Phys. A115, 545 (1968).
    • J. Grumann, U. Mosel, B. Fink and W. Greiner, Z. Physik 228, 371 (1969).
  2. ^ Velocity Measurements of Recoil Nuclei from α-Decay and the Determination of their Mass, C.J. Batty, A.I. Kilvington and A. Marinov, Nucl. Inst. and Methods 99, (1972) 179-182; Production of Actinides by Secondary Reactions in the Bombardment of a Tungsten Target with 24 GeV Protons, A. Marinov (Invited Talk), S. Eshhar and J.L. Weil, Proc. Int. Symp. on Superheavy Elements, Lubbock, Texas, 1978, 72-80; Study of Au, Tl and Pb Sources Separated from Tungsten Targets that were Irradiated with 24 GeV Protons, Indications for the Possible Production of Superheavy Elements, A. Marinov (Invited Talk), S. Eshhar, and B. Alspector, Proc. Int. Symp. on Superheavy Elements, Lubbock, Texas, 1978, 81-88. Evidence for the Possible Existence of a Superheavy Element with Atomic Number 112, A. Marinov, C.J. Batty, A.I. Kilvington, G.W.A. Newton, V.J. Robinson and J.D. Hemingway, Nature 229, (1971) 464-467; Spontaneous Fission Previously Observed in a Mercury Source, A. Marinov, C.J. Batty, A.I. Kilvington, J.L. Weil, A.M. Friedman, G.W.A. Newton, V.J. Robinson, J.D. Hemingway and D.S. Mather, Nature 234, (1971) 212- 215.
  3. ^ Consistent Interpretation of the Secondary-Reaction Experiments in W Targets and Prospects for Production of Superheavy Elements in Ordinary Heavy-Ion Reactions, A. Marinov, S. Eshhar, J.L. Weil and D. Kolb, Phys. Rev. Letters 52, (1984) 2209-2212; 53, 1984 1120 (E).
  4. ^ Fusion of 16O+148,150,152,154Sm at Sub-Barrier Energies, R. G. Stokstad, Y. Eisen, S. Kaplanis, D. Pelte, U. Smilansky and I. Tserruya, Phys. Rev. C 21 (1980) 2427-2435.
  5. ^ Discovery of Strongly Enhanced Low Energy α Decay of a Long-Lived Isomeric State Obtained in 16O + 197Au Reaction At 80 Mev, Probably to Superdeformed Band, A. Marinov, S. Gelber and D. Kolb, Mod. Phys. Lett. A11 (1996) 861-869. Response to the IUPAC/IUPAP Joint Working Party Second Report 'On the Discovery of Elements 110-118', A. Marinov, S. Gelberg, D. Kolb and G. W. A. Newton, 2004, arXiv:nucl-ex/0411017.
  6. ^ Consistent Interpretation of the Secondary-Reaction Experiments in W Targets and Prospects for Production of Superheavy Elements in Ordinary Heavy-Ion Reactions, A. Marinov, S. Eshhar, J.L. Weil and D. Kolb, Phys. Rev. Letters 52, (1984) 2209-2212; 53, 1984 1120 (E).
  7. ^ Evidence for Long-Lived Isomeric States in Neutron-Deficient 236Am and 236Bk Nuclei, A. Marinov, S. Eshhar and D. Kolb, Phys. Letters 191B, (1987) 36-40.
  8. ^ Existence of Long-lived Isomeric States in Naturally-occurring Neutron-deficient Th Isotopes, A. Marinov, I. Rodushkin, Y. Kashiv, L. Halicz, I. Segal, A. Pape, R. V. Gentry, H. W. Miller, D. Kolb and R. Brandt, Phys. Rev. C 76, 0211303(R) (2007).
  9. ^ Evidence for Long-Lived Proton Decay not Far From The beta-Stability Valley, Produced by the 16O + 197Au Reaction at 80 Mev, A. Marinov, S. Gelberg and D. Kolb, Mod. Phys. Lett. A11 (1996) 949-956.
  10. ^ Evidence for the possible existence of a long-lived superheavy nucleus with atomic mass number A=292 and atomic number Z=~122 in natural Th, A. Marinov, I. Rodushkin, D. Kolb, A. Pape, Y. Kashiv, R. Brandt, R.V. Gentry, H.W. Miller, Int. J. Mod. Phys. E 19 (2010) 131-140.
  11. ^ Evidence for a long-lived superheavy nucleus with atomic mass number A=292 and atomic number Z=~122 in natural Th, A. Marinov, I. Rodushkin, D. Kolb, A. Pape, Y. Kashiv, R. Brandt, R.V. Gentry, H.W. Miller, arXiv:0804.3869 (2008).

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