Alpha particles energy estimation from track diameter development in a CR-39 detector

Protons in the Sun’s core are a dense plasma allowing fusion events where two protons initially join to produce a deuteron. Eventually this leads to alpha particles, the mass-four nucleus of helium, releasing kinetic energy. Schrodinger’s equation allows particles to penetrate classically forbidden Coulomb barriers with small but important probabilities. The approximation known as Wentzel–Kramers–Brillouin (WKB) is used by Gamow to predict the rate of proton–proton fusion in the Sun, shown to be in agreement with measurements. A simplified formula is given for the power density due to fusion in the plasma constituting the Sun’s core. The properties of atomic nuclei are briefly summarized.

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Quantum Tunneling

10.1093/oso/9780198808275.003.0014 ◽

2017 ◽

Author(s):

Frank S. Levin

Keyword(s):

Quantum Tunneling ◽

Alpha Particles ◽

Attractive Potential ◽

Scanning Tunneling ◽

Finite Width ◽

Potential Well ◽

Surface Molecules ◽

Repulsive Coulomb ◽

The Subject ◽

The One

Quantum tunneling, wherein a quanject has a non-zero probability of tunneling into and then exiting a barrier of finite width and height, is the subject of Chapter 13. The description for the one-dimensional case is extended to the barrier being inverted, which forms an attractive potential well. The first application of this analysis is to the emission of alpha particles from the decay of radioactive nuclei, where the alpha-nucleus attraction is modeled by a potential well and the barrier is the repulsive Coulomb potential. Excellent results are obtained. Ditto for the similar analysis of proton burning in stars and yet a different analysis that explains tunneling through a Josephson junction, the connector between two superconductors. The final application is to the scanning tunneling microscope, a device that allows the microscopic surfaces of solids to be mapped via electrons from the surface molecules tunneling into the tip of the STM probe.

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Artificial Radioactivity

10.1093/oso/9780198827870.003.0011 ◽

2018 ◽

Author(s):

Roger H. Stuewer

Keyword(s):

Radioactive Isotope ◽

Alpha Particles ◽

Enrico Fermi ◽

Marie Curie ◽

Artificial Radioactivity ◽

Geiger Muller Counter

Frédéric Joliot discovered artificial radioactivity on January 11, 1934, when he bombarded aluminum with polonium alpha particles and produced a radioactive isotope of phosphorus that decayed by emitting a positron. He detected it with a Geiger–Müller counter that Wolfgang Gentner had constructed for him. Two months later, Enrico Fermi, motivated in part by an insight of his first assistant, Gian Carlo Wick, decided to see if neutrons also could produce artificial radioactivity. The transformation of a neutron into a proton in a nucleus should create an electron, so to increase their number and hence the probability of creating an electron, he bombarded various elements with intense sources of neutrons, and on March 20, 1934, with aluminum he observed the created electrons and thereby discovered neutron-induced artificial radioactivity. Less than four months later, Marie Curie died on July 4, 1934, at age sixty-six.

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New Particles

10.1093/oso/9780198827870.003.0007 ◽

2018 ◽

Author(s):

Roger H. Stuewer

Keyword(s):

Gamma Rays ◽

Atomic Hydrogen ◽

Nuclear Physics ◽

Hydrogen Isotope ◽

Alpha Particles ◽

Cloud Chamber ◽

Ernest Rutherford ◽

James Chadwick ◽

Theoretical Foundations ◽

New Particles

In December 1931, Harold Urey discovered deuterium (and its nucleus, the deuteron) by spectroscopically detecting the faint companion lines in the Balmer spectrum of atomic hydrogen that were produced by the heavy hydrogen isotope. In February 1932, James Chadwick, stimulated by the claim of the wife-and-husband team of Irène Curie and Frédéric Joliot that polonium alpha particles cause the emission of energetic gamma rays from beryllium, proved experimentally that not gamma rays but neutrons are emitted, thereby discovering the particle whose existence had been predicted a dozen years earlier by Chadwick’s mentor, Ernest Rutherford. In August 1932, Carl Anderson took a cloud-chamber photograph of a positron traversing a lead plate, unaware that Paul Dirac had predicted the existence of the anti-electron in 1931. These three new particles, the deuteron, neutron, and positron, were immediately incorporated into the experimental and theoretical foundations of nuclear physics.

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Nuclear Electrons and Nuclear Structure

10.1093/oso/9780198827870.003.0006 ◽

2018 ◽

Author(s):

Roger H. Stuewer

Keyword(s):

Nuclear Structure ◽

Beta Decay ◽

Gamma Rays ◽

Alpha Particle ◽

Continuous Distribution ◽

Alpha Particles ◽

Light Nuclei ◽

Coincidence Method ◽

Wolfgang Pauli ◽

Beta Particles

Serious contradictions to the existence of electrons in nuclei impinged in one way or another on the theory of beta decay and became acute when Charles Ellis and William Wooster proved, in an experimental tour de force in 1927, that beta particles are emitted from a radioactive nucleus with a continuous distribution of energies. Bohr concluded that energy is not conserved in the nucleus, an idea that Wolfgang Pauli vigorously opposed. Another puzzle arose in alpha-particle experiments. Walther Bothe and his co-workers used his coincidence method in 1928–30 and concluded that energetic gamma rays are produced when polonium alpha particles bombard beryllium and other light nuclei. That stimulated Frédéric Joliot and Irène Curie to carry out related experiments. These experimental results were thoroughly discussed at a conference that Enrico Fermi organized in Rome in October 1931, whose proceedings included the first publication of Pauli’s neutrino hypothesis.

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