Artificial Radioactivity Produced by Alpha-Particles

Ridenour, Louis N.; Henderson, W.

doi:10.1103/physrev.52.889

Cited by 43 publications

(4 citation statements)

References 20 publications

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“…The authors "believe the 9-minute activity to be due to Fe 53 rather than to Fe 55 because: (1) it is not produced by deuteron or slow neutron bombardment of Fe, (2) it is produced by fast neutrons on Fe, (3) attempts to produce 55 Fe by other reactions have not disclosed a 9 minute activity." The half-life was determined to be 8.9(2) m which is close to the accepted value of 8.51(2) m. In 1937, Ridenour and Henderson had observed a 9-minute activity; however, they were unable to make the unique mass assignment and attributed it to either the reaction 50 Cr(α,n) 53 Fe or the reaction 52 Cr(α,n) 55 Fe [20]. In an even earlier publication, they had preferred the later assignment [21].…”

Section: Fesupporting

confidence: 66%

Discovery of the iron isotopes

Schuh

Fritsch

Heim

et al. 2010

Atomic Data and Nuclear Data Tables

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Section: Fesupporting

confidence: 66%

Discovery of the iron isotopes

Schuh

Fritsch

Heim

et al. 2010

Atomic Data and Nuclear Data Tables

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“…Previous measurements [3][4][5][6][7][8][9] of the 66 Ga half-life are summarized in Table I. The table also lists the values adopted in the recent evaluations by Woods [10] and by Browne [2].…”

mentioning

confidence: 98%

Half-life ofGa66

et al. 2010

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We measured the half-life of 66 Ga by observing positrons from the β + branch to the ground state of 66 Zn with a superconducting Wu-type beta spectrometer. Our result is t 1/2 = 9.304(8) hours, which is the highest-precision measurement to date and disagrees with the Nuclear Data Sheets (NDS) value by over 6σ .The nucleus 66 Ga decays by electron capture and positron emission to 66 Zn with a half-life of more than nine hours, emitting β's up to 4.15 MeV and several γ 's with energies exceeding 2 MeV. 66 Ga is easy to produce by proton bombardment of natural zinc and is therefore a useful isotope for detector efficiency and energy calibrations [1].While in the process of carrying out a calibration experiment for a β spectrometer, we noticed that the half-life of 66 Ga is significantly shorter than the value quoted in the most recent Nuclear Data Sheets evaluation [2], and in light of this, we decided to carry out a dedicated experiment to measure the half-life.Previous measurements [3-9] of the 66 Ga half-life are summarized in Table I. The table also lists the values adopted in the recent evaluations by Woods [10] and by Browne [2]. The values adopted in the two evaluations are not in good agreement.Our experiment consisted of detecting positrons from the ground-state decay of 66 Ga in the Wisconsin Superconducting Beta Spectrometer (WSBS). The WSBS is an iron-free double focusing Wu-type beta spectrometer with a momentum acceptance of roughly 2% full width at half maximum (FWHM) and peak solid angle greater than 0.5 sr [11]. Positrons that pass through the spectrometer are detected with a 10 mm diameter, 5-mm thick Si(Li) detector. The detector has excellent energy resolution for stopped particles (about 10 keV FWHM), and the resulting capability to independently measure the energy of the momentum-selected β's allows for checks on systematic errors in the experiment.The 66 Ga was produced by proton irradiation of a 3 mg/cm 2 natural zinc target. The zinc had been vapor deposited onto a 13-µm thick aluminum foil, mounted on one of the spectrometer source holders. The reaction proceeded as 66 Zn(p,n) 66 Ga with bombardment at 7 MeV using 2 µA of beam for about 30 minutes at the Wisconsin Tandem Accelerator Lab. The target was allowed to sit for one hour to permit short-lived isotopes such as 64 Ga and 66 Cu to decay to negligible levels. It was then inserted into the counting position of the spectrometer.Data collection runs were taken at four different WSBS magnet current settings. Two of the settings were used to measure background rates, 0 A which is nonfocusing, and 20 A, corresponding to a beta momentum of 4.96 MeV/c, which is well above the beta decay endpoint as well as the internal conversion electron lines from states in 66 Zn. The other two currents, 11 and 14 A, with momenta centered at 2.73 and 3.47 MeV, respectively, were used for decay counting. The choice of relatively high momenta for decay counting helps to reduce the possibility of contributions from contaminants.Counting proceeded for 52 hours...

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“…The choice of chlorine as the neutron emitter in potassium chloride is given added weight by the recent work of Pollard, Schultz, and Brubaker (3) , who showed that both argon and chlorine emit neutrons'under ThC' and RaC' -particle bombardment. The chlorine disintegration has been further studied by Hurst and Walke (2) and by Ridenour and Henderson (4) , using artificially accelerated 11 Mev. and 9 Mev.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

NEUTRONS BY ALPHA-PARTICLE BOMBARDMENT OF LIGHT ELEMENTS¹

Copeland¹,

Lind²

1938

J. Phys. Chem.

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In view of the widespread interest in neutrons, it was felt that it might be of interest to examine the light elements under the same experimental conditions with respect to their neutron emission under -particle bombardment, using radon as the source of a-particles.For detection of the neutrons, it was decided to use the radioactivity induced in iodine. This element is one which is strongly activated by neutrons, and forms a single radioactive isotope, I128, with a very convenient half-period of 25 minutes. By the use of ethyl iodide and the method of Szilard and Chalmers (5), the activity induced in a very large quantity of iodine can be concentrated and easily measured.It must be admitted that the activity so obtained is not an absolute measure of the number of neutrons emitted by a given source, nor is the ratio of two activities produced by two different sources necessarily the ratio of the numbers of neutrons emitted by the two sources. This is because iodine (or any detector element) is not activated to the same extent by neutrons of different energies, and the energy spectrum of the neutrons emitted by different elements may vary widely. For a discussion of the difficulty of determining the absolute number of neutrons emitted by a given source, the reader is referred to the paper by Amaldi, Hafstad, and Tuve (1). EXPEBIMENTALThe element, or compound of the element, to be examined was sealed, except where otherwise stated, with radon in a soft-glass bulb approximately 7 mm. in diameter. This bulb was kept in a soft-glass tube, sealed at one end, which could be dipped into ethyl iodide.The radioiodine was prepared by placing the neutron source at the 1 This paper was abstracted from a thesis submitted by C. S. Copeland to the Graduate Faculty of the University of Minnesota in partial fulfillment of the reluirements for the degree of Doctor of Philosophy, June, 1937.

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Artificial Radioactivity Produced by Alpha-Particles

Cited by 43 publications

References 20 publications

Discovery of the iron isotopes

Discovery of the iron isotopes

Half-life ofGa66

NEUTRONS BY ALPHA-PARTICLE BOMBARDMENT OF LIGHT ELEMENTS¹

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Artificial Radioactivity Produced by Alpha-Particles

Cited by 43 publications

References 20 publications

Discovery of the iron isotopes

Discovery of the iron isotopes

Half-life ofGa66

NEUTRONS BY ALPHA-PARTICLE BOMBARDMENT OF LIGHT ELEMENTS1

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NEUTRONS BY ALPHA-PARTICLE BOMBARDMENT OF LIGHT ELEMENTS¹