quantum spin

further chem

spin

it is:

• a fundamental, intrinsic quantum property of quantum particles

• acts as a form of angular momentum

  • except, if the electron were to spin in the classic sense, they would spin faster than the speed of light to match observed angular momentum values because it’s so small

• quantised: “spin-up” or “spin-down”

• also supported by the fact that electrons act like little magnets, and magnetic fields arise from rotating charged bodies

• expressed as

• conventionally defined as

• depends only on the type of particle, cannot be altered in any known way

particles with half-integer spins, such as are known as fermions, while those particles with integer spins, such as are known as bosons

the distinction between two is that fermions obey the Pauli exclusion principle

the spin quantum number is a quantum number designated that describes the intrinsic angular momentum of a particle. it has the same value for all particles of the same type

represents the total nuclear spin, while represents the component of the spin along a specified axis

• the value of is the component of spin angular momentum, parallel to a given direction (conventionally labelled the -axis)

isospin

• protons and neutrons behave almost identically under the strong nuclear force, despite having different electric charges
• suggests an underlying symmetry

total isospin is denoted by
a quantum number describing symmetry in the strong nuclear force

• treats protons and neutrons as two states of the same nucleon
• arises from the symmetry between up (u) and down (d) quarks

the third component of isospin:

• is denoted
• describes the projection of isospin along a chosen axis in space
• analogous to the quantum number
• is related to the electron charge () of a particle

other

instead of a point size particle that acts like it is spinning, it can be thought of as a spread-out blob of charge that truly rotates (but why doesn’t bits repel each other and explode?)