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Title: Direct Observation of Two Proton Radioactivity Using Digital Photography

Abstract

Recently the observation of a new type of spontaneous radioactive decay has been claimed in which two protons are simultaneously ejected by an atomic nucleus from the ground state1,2,3. Experimental data obtained for the extremely neutron-deficient nuclei 45Fe and 54Zn, were interpreted as the first evidence of such a decay mode which has been sought since 1960.4 However, the technique applied in those studies allowed only measurements of the decay time and the total energy released. Particles emitted in the decay were not identified and the conclusions had to be supported by theoretical arguments. Here we show for the first time, directly and unambiguously, that 45Fe indeed disintegrates by two-proton decay. Furthermore, we demonstrate that the decay branch of this isotope leads to various particle emission channels including two-proton and three-proton emission. To achieve this result we have developed a new type of detector V the Optical Time Projection Chamber (OTPC) in which digital photography is applied to nuclear physics for the first time. The detector records images of tracks from charged particles, allowing for their unambiguous identification and the reconstruction of decay events in three dimensions. This new and simple technique provides a powerful method to identify exotic decaymore » channels involving emission of charged particles. It is expected that further studies with the OTPC device will yield important information on nuclei located at and beyond the proton drip-line, thus providing new material for testing and improving models of very unstable atomic nuclei.« less

Authors:
 [1];  [2];  [3];  [2];  [4];  [5];  [3];  [3];  [5];  [3];  [6];  [1];  [2];  [2];  [3];  [5];  [5];  [6]
  1. ORNL
  2. IEP, Warsaw University
  3. Warsaw University
  4. IEP, University of Warsaw
  5. University of Tennessee, Knoxville (UTK)
  6. NSCL Michigan State University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Holifield Radioactive Ion Beam Facility
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931406
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nature
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CHARGED PARTICLES; DECAY; DIMENSIONS; NUCLEAR PHYSICS; NUCLEI; PHOTOGRAPHY; PROTONS; RADIOACTIVITY; TESTING; TIME PROJECTION CHAMBERS

Citation Formats

Rykaczewski, Krzysztof Piotr, Pfutzner, M., Dominik, Wojciech, Janas, Z., Miernik, K., Bingham, C. R., Czyrkowski, Henryk, Cwiok, Mikolaj, Darby, Iain, Dabrowski, Ryszard, Ginter, T. N., Grzywacz, Robert Kazimierz, Karny, M., Korgul, A., Kusmierz, Waldemar, Liddick, Sean, Rajabali, Mustafa, and Stolz, A. Direct Observation of Two Proton Radioactivity Using Digital Photography. United States: N. p., 2007. Web.
Rykaczewski, Krzysztof Piotr, Pfutzner, M., Dominik, Wojciech, Janas, Z., Miernik, K., Bingham, C. R., Czyrkowski, Henryk, Cwiok, Mikolaj, Darby, Iain, Dabrowski, Ryszard, Ginter, T. N., Grzywacz, Robert Kazimierz, Karny, M., Korgul, A., Kusmierz, Waldemar, Liddick, Sean, Rajabali, Mustafa, & Stolz, A. Direct Observation of Two Proton Radioactivity Using Digital Photography. United States.
Rykaczewski, Krzysztof Piotr, Pfutzner, M., Dominik, Wojciech, Janas, Z., Miernik, K., Bingham, C. R., Czyrkowski, Henryk, Cwiok, Mikolaj, Darby, Iain, Dabrowski, Ryszard, Ginter, T. N., Grzywacz, Robert Kazimierz, Karny, M., Korgul, A., Kusmierz, Waldemar, Liddick, Sean, Rajabali, Mustafa, and Stolz, A. Mon . "Direct Observation of Two Proton Radioactivity Using Digital Photography". United States. doi:.
@article{osti_931406,
title = {Direct Observation of Two Proton Radioactivity Using Digital Photography},
author = {Rykaczewski, Krzysztof Piotr and Pfutzner, M. and Dominik, Wojciech and Janas, Z. and Miernik, K. and Bingham, C. R. and Czyrkowski, Henryk and Cwiok, Mikolaj and Darby, Iain and Dabrowski, Ryszard and Ginter, T. N. and Grzywacz, Robert Kazimierz and Karny, M. and Korgul, A. and Kusmierz, Waldemar and Liddick, Sean and Rajabali, Mustafa and Stolz, A.},
abstractNote = {Recently the observation of a new type of spontaneous radioactive decay has been claimed in which two protons are simultaneously ejected by an atomic nucleus from the ground state1,2,3. Experimental data obtained for the extremely neutron-deficient nuclei 45Fe and 54Zn, were interpreted as the first evidence of such a decay mode which has been sought since 1960.4 However, the technique applied in those studies allowed only measurements of the decay time and the total energy released. Particles emitted in the decay were not identified and the conclusions had to be supported by theoretical arguments. Here we show for the first time, directly and unambiguously, that 45Fe indeed disintegrates by two-proton decay. Furthermore, we demonstrate that the decay branch of this isotope leads to various particle emission channels including two-proton and three-proton emission. To achieve this result we have developed a new type of detector V the Optical Time Projection Chamber (OTPC) in which digital photography is applied to nuclear physics for the first time. The detector records images of tracks from charged particles, allowing for their unambiguous identification and the reconstruction of decay events in three dimensions. This new and simple technique provides a powerful method to identify exotic decay channels involving emission of charged particles. It is expected that further studies with the OTPC device will yield important information on nuclei located at and beyond the proton drip-line, thus providing new material for testing and improving models of very unstable atomic nuclei.},
doi = {},
journal = {Nature},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • A proton beam driven by a repetitive high-intensity-laser is utilized to induce a {sup 7}Li(p,n) {sup 7}Be nuclear reaction. The total activity of {sup 7}Be are evaluated by two different methods. The activity obtained measuring the decay gamma-rays after 1912 shots at 1 Hz is 1.7 {+-} 0.2 Bq. This is in good agreement with 1.6 {+-} 0.2 Bq evaluated from the proton energy distribution measured using a time-offlight detector and the nuclear reaction cross-sections. We conclude that the production of activity can be monitored in real time using the time-of-flight-detector placed inside a diverging proton beam coupled with amore » high-speed signal processing system.« less
  • The decay of the extremely neutron deficient 48Ni was studied by means of an imaging time projection chamber which allowed the recording of tracks of charged particles. Decays of 6 atoms were observed. Four of them clearly correspond to two-proton radioactivity providing the first direct evidence for this decay mode in 48Ni. Two decays represent -delayed proton emission. The half-life of 48Ni is determined to be T1=2 = 2:1+1:4 0:4 ms.
  • We have observed the two-proton radioactivity of the previously unknown {sup 19}Mg ground state by tracking the decay products in-flight. For the first time, the trajectories of the 2p-decay products, {sup 17}Ne+p+p, have been measured by using tracking microstrip detectors which allowed us to reconstruct the 2p-decay vertices and fragment correlations. The half-life of {sup 19}Mg deduced from the measured vertex distribution is 4.0(15) ps in the system of {sup 19}Mg. The Q value of the 2p decay of the {sup 19}Mg ground state inferred from the measured p-p-{sup 17}Ne correlations is 0.75(5) MeV.
  • After the recent discovery of two-proton radioactivity, an important effort has been made in order to observe each emitted particle individually. Such kind of studies may result in energy and angular correlation measurements of the protons, which are required to give a precise theoretical description of this exotic decay mode. In this frame, we performed an experiment at the GANIL/SISSI/LISE3 facility, where we used a Time Projection Chamber to observe tracks of protons in the decay of {sup 45}Fe, produced in projectile fragmentation reactions.
  • The decay of the extremely neutron-deficient {sup 48}Ni was studied by means of an imaging time-projection chamber, which allowed the recording of tracks of charged particles. The decays of six atoms were observed. Four of them clearly correspond to two-proton radioactivity, providing the first direct evidence for this decay mode in {sup 48}Ni. Two decays represent {beta}-delayed proton emission. The half-life of {sup 48}Ni is determined to be T{sub 1/2}=2.1{sub -0.4}{sup +1.4} ms.