Jump to content

Amnon Marinov

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Narky Blert (talk | contribs) at 09:21, 14 March 2018 (→Advanced Technical Description: dab tag and link removed (duplicates link to half-life)). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Prof. Amnon Marinov

Amnon Marinov (1930 –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 Tzora in the Judea Mountains. While still a kibbutz member he began his physics studies at the Hebrew University of Jerusalem, Israel. In 1957, he relocated to Jerusalem and continued his studies, specializing in nuclear physics. He completed his doctoral dissertation on the Mossbauer Effect in 1963, and in 1971 was nominated as a professor at the Hebrew University of Jerusalem.

Research Interests

The Importance Of Marinov’s Work

The study of Super Heavy Elements is of particular importance. It provides insights for better understanding the structure of matter, and the evolution of the universe. It can also lead to new applications for elements discovered or synthesized. While theoretical studies already predicted existence of islands of super heavy elements stability back in the 1960s, Marinov’s work and announcements of what he believed to be the discovery of Element 112 significantly fueled the experimental research for Super Heavy Elements. Furthermore, Marinov pioneered with experimental methods based on secondary reactions. In his work he also developed new interpretations relating to isomeric states, which supported existence of long-lived super heavy elements in nature.

These new interpretations, however, despite their continued repetition by Marinov and his collaborators, have never been accepted by the scientific community because they are completely irreproducible by any other group – which is as expected, as they would require serious revisions to widely accepted and successful theories of nuclear physics if they turned out to be true.

The Search for Super-Heavy Elements

Marinov devoted a significant part of his career to the search for Super-Heavy Elements (SHE). These refer to transuranium elements, having atomic number greater than 92, and considered to be unstable. Already in the 1960s theoretical calculations predicted the possible existence of an Island of Stability of super-heavy elements. Some of these calculations predicted very long lifetimes for certain Super Heavy Element isotopes - of up to a half-life of millions years. These predictions excited the nuclear physics community, triggering the search for super-heavy elements. Scientists have used three key methods:
1. Search of existing super-heavy elements in nature.
2. Creation of super heavy elements by neutron absorption - slow neutron capture reactions (interspersed with beta radiation).
3. Use of heavy ion accelerator.
Marinov pioneered with the development of an alternative Super Heavy Elements research approach, based on secondary reactions. Later on he developed an original interpretation to isomeric states phenomena, predicting relatively long half-life to large size nuclei that also supported observation of Super Heavy Elements in nature.

The Claim of Element 112 Discovery

In 1971, while Marinov was a research associate at Rutherford High Energy Laboratories, Oxfordshire, England, he and his associates investigated Tungsten targets which served as 24 GeV proton beam stopper at the CERN Accelerator. Marinov’s thesis was that the proton beam hitting the tungsten target caused very high energy recoil of Tungsten nuclei fractions, which in term would collide and fuse with neighboring Tungsten nuclei in a secondary reaction, leading to the creation of super-heavy elements. Marinov et al. discovered what they believed to be evidence for the existence of a long-lived super-heavy element with atomic number 112, homologous to Mercury and having a half-life of 47 days. In 1984, basing their arguments on mass separator measurements, Marinov et al. concluded that the previously formed nuclei are neutron-deficient super-heavy element with Z=112 and approximately 160 neutrons. The Super Heavy Element nuclei stability, as well as its unexpected radiation properties were associated by Marinov to isomeric states. In total Marinov et al. claimed to have identified hundreds of nuclei of the new Super Heavy Element number 112. The team used chemical separation technics to isolate the nuclei.

Some issues were encountered regarding the theoretically predicted versus the empirically discovered properties of this Super Heavy Element. One problem was that the deduced cross-section of these Super Heavy Elements was several orders of magnitude larger than their typical measured cross-sections. Marinov et al. provided explanation for this gap by studying the spectra of actinides separated from the Tungsten target.

Marinov’s surprising findings were challenged by the scientific community, although no experimental errors were identified, and neither were the experiments ever repeated in identical sequence and details. Albeit numerous papers which were published by Marinov et al. concerning the findings, the discovery of Element 112 by Marinov et al. was not endorsed by the scientific community.

In 1996, the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany, reported evidence for a single nucleus with an atomic number 112 having half life time of less than a second. In 2009 the GSI team was officially recognized as the discoverer of this new element, named Copernicium, after the astronomer Nicolaus Copernicus. Marinov and his collaborators submitted an appeal for crediting GSI for the primacy of element 112 discovery, which was not accepted.[1]

Search for Super Heavy Elements in Nature

In the 1990s Marinov began to search for the existence of Super Heavy Elements in nature, a search which continued in the new millennium. Marinov et al. developed a consistent interpretation to some previously unexplained phenomena related to the discovery of long-lived high-spin super- and hyperdeformed isomeric states. Marinov expected that Super Heavy nuclei could have relatively long half lives while in isomeric states, and thus could be observed in nature.

Applying their interpretation, Marinov et al. found in a study of pure Au evidence for the existence of long-lived isotopes with atomic mass numbers 261 and 265,and abundance of less than a thousandth of ppm relative to Au. The measured masses match the predictions for the masses of undiscovered 261Rg and 265Rg (Z = 111).

In 2009, after studying natural Th, Marinov et al. reported evidence for the possible existence of a long-lived superheavy nucleus with atomic mass number A = 292, atomic number Z = 122 or a nearby element, and abundance of about 1×10−12 relative to 232Th. The deduced half-life greater of 108 years was associated with the relative stability of the isomeric states.

None of these findings could be confirmed by any other group and his discovery claims were universally disregarded by the scientific community.

Advanced Technical Description

Not an appropriate template for mainspace, see MOS:COLLAPSE.

Already in the 1960s 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.[2]

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.[3] 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.[4]

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;[5] 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.[6]
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.[7] 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.[8]
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.[9]
Long-lived isomeric states were also observed in 16O + 197Au reaction at 80 MeV.[10] 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.[11]
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, 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.[12]

Family

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

  1. ^ 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.
  2. ^ 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).
  3. ^
    • 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.
  4. ^ 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, Physical Review Letters 52, (1984) 2209-2212; 53, 1984 1120 (E).
  5. ^ 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.
  6. ^ 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.
  7. ^ 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, Physical Review Letters 52, (1984) 2209-2212; 53, 1984 1120 (E).
  8. ^ 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.
  9. ^ 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).
  10. ^ 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.
  11. ^ 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.
  12. ^ 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).
Retrieved from "https://en.wikipedia.org/w/index.php?title=Amnon_Marinov&oldid=830354106"