Isotope from proton bombardments

Figure I. Calculated isotope yields from proton bombardments with incident beam energy. No is predicted.

Another type of radioactivity, known as nuclear transmutation, results from the bombardment of nuclei by neutrons, protons, or other nuclei An example of a nuclear transmutation is the conversion of atmospheric to gC and H, which results when the nitrogen isotope captures a neutron (from the sun). In some cases, heavier elements are synthesized from hghter elements. This type of transmutation occurs naturally in outer space, but it can also be achieved artificially, as we will see in Section 23.4. 

The energy spectrum of protons emitted from targets bombarded by 14 Mev neutrons has been measured by Allan using photographic plates as detectors and thin foils of separated isotopes as targets, and by Colli and Facchini using scintillation detectors. Some of the protons Allan detected... 

Mathur and Hyde studied neutron deficient xenon isotopes produced by bombardment of KI with 100-Mev protons using a similar procedure. The KI was dissolved with water in a closed system and the xenon removed from solution by pumping through the same series of traps used in the radon procedure. The NaOH scrubbing was omitted. 

Twenty five isotopes of polonium are known, with atomic masses ranging from 194 to 218. Polonium-210 is the most readily available. Isotopes of mass 209 (half-life 103 years) and mass 208 (half-life 2.9 years) can be prepared by alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron, but these are expensive to produce. 

The half-lives of the elements vary widely, as shown in Table 3.2. Some isotopes, nitrogen-14 for example, are stable and experience no natural radioactive decay. However, bombarding even a stable element with energetic alpha rays can cause transmutation. Rutherford discovered the proton when he created hydrogen from a stable isotope of nitrogen. 

The three isotopes with the longest half-life times, Tc, Tc, and Tc, were produced in small quantities as early as 1955 by the bombardment of molybdenum with 22MeV protons. Although Tc is the isotope with the longest half-life time, it is not the major isotope available from nuclear... 

In the Detroit apparatus, illustrated in Figure 2.4, the (3+ source is created in situ by bombarding a boron target with a 4.75 MeV proton beam emanating from a van der Graaf accelerator. An unstable carbon isotope is then produced via the reaction... 

Nitrogen-14 was bombarded by alpha particles (helium nuclei), producing oxygen-17 and protons (hydrogen nuclei). In 1934, Irene Johot-Curie (1897- 1956), the daughter of Marie Curie, produced an isotope of phosphorus by bombarding aluminum-27 with alpha particles from polonium ... 

The first claim for the discovery of the element nobefium was made in Sweden in 1957. However, neither American nor Soviet researchers could du-phcate the original results, which are now known to have been interpreted incorrectly. The actual discovery of nobelium is credited to researchers in Berkeley, California, who in 1958 bombarded a curium target (95% " Cm and 4.5% Cm) plated on a nickel foil with 60 to 100 MeV ions, and detected both the 8.4 MeV a-particles created by the radioactive decay of No and the °Fm created from the a-decay of No. Known isotopes of nobelium possess 148 to 160 neutrons and 102 protons all are radioactive, with half-fives ranging between 2.5 milliseconds and 58 minutes, and decay by spontaneous fission, a-particle emission, or electron capture. No has the longest half-fife 58 minutes. 

The discovery of technetium in 1937 by the Italian scientists Carlo Perrier and Emilio Segre was an important affirmation of the configuration of the Periodic Table. The table had predicted the existence of an element with 43 protons in its nucleus, but no such element had ever been found. (In fact, technetium does not occur naturally on Earth, as all of its known isotopes are radioactive and decay to other elements on a timescale that is relatively small when compared with the age of the earth.) Perrier and Segre were able to observe technetium from molybdenum that had been bombarded with deuterons. They named the element technetium, from the Greek word technetos, meaning artificial. Technetium is produced in relatively large quantities during nuclear fission, so there is currently an ample supply of the element from nuclear reactors and nuclear weapons production. 

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