J. J. Thomson

The one-electron universe postulate, proposed by John Wheeler in a telephone call to Richard Feynman in the spring of 1940, is the hypothesis that all electrons and positrons are actually manifestations of a single entity moving backwards and forwards in time.

Historically, the mass of the electron was determined directly from combining two measurements. The mass-to-charge ratio of the electron was first estimated by Arthur Schuster in 1890 by measuring the deflection of “cathode rays” due to a known magnetic field in a cathode ray tube. It was seven years later that J. J.

Ernest Rutherford’s

Recommended Values of Physical Constants and Conversion Factors

The free neutron has a mass of 3 eV/c2, or 1.sup>−27 kg, or 1.u. The neutron has a mean square radius of about 0.8×10−15 m, or 0.8 fm, and it is a spin-½ fermion.

Mononeutron: An isolated neutron undergoes beta decay with a mean lifetime of approximately 15 minutes (half-life of approximately 10 minutes), becoming a proton (the nucleus of hydrogen), an electron and an antineutrino. Its existence has been proven to be relevant for nuclear structure of exotic nuclei.

The electrons do not orbit the nucleus in the manner of a planet orbiting the sun, but instead exist as standing waves. The electrons are never in a single point location, although the probability of interacting with the electron at a single point can be found from the wave function of the electron.

For an elementary particle to have an intrinsic magnetic moment, it must have both spin and electric charge. The neutron has spin 1/2 ħ, but it has no net charge. The neutron is composed of three quarks, and the magnetic moments of these elementary particles combine to give the neutron its magnetic moment.

The magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field. The direction of the magnetic moment points from the south to north pole of the magnet (inside the magnet). The magnetic field of a magnetic dipole is proportional to its magnetic dipole moment.

Neutrons interact with magnetic fields due to their so-called spin. If beams of polarised neutrons pass through a magnetic field, a refraction of the neutron beam can be detected behind this field. From the refraction pattern, the magnetic field and in particular the differences in field strengths can be reconstructed.

Since the proton has charge +1 e, it should have magnetic moment equal to 1 μN by this expression. The larger magnetic moment of the proton indicates that it is not an elementary particle. The sign of the proton’s magnetic moment is that of a positively charged particle.

A g-factor (also called g value or dimensionless magnetic moment) is a dimensionless quantity that characterizes the magnetic moment and angular momentum of an atom, a particle or the nucleus.

In SI units, its value is approximately: μN = 5.×10−27 J/T. The nuclear magneton is the natural unit for expressing magnetic dipole moments of heavy particles such as nucleons and atomic nuclei.

Its SI unit is the radian per second per tesla (rad⋅s−1⋅T−1) or, equivalently, the coulomb per kilogram (C⋅kg−1). The term “gyromagnetic ratio” is often used as a synonym for a different but closely related quantity, the g-factor….For a nucleus.