Spin and Orbital Angular Momentum

Best 14 Differences Between Spin and Orbital Angular Momentum

Spin Angular Momentum vs. Orbital Angular Momentum

Spin and orbital angular momentum are central concepts in quantum mechanics, serving to define particles’ unique forms of angular motion. Spin angular momentum relates to an object’s quantum spin but is unrelated to physical movement.

Magnetic moments have discrete values and contribute to a particle’s magnetic properties, while orbital angular momentum results from particle movement around an axis and is associated with its spatial distribution.

Quantization into discrete quantum numbers quantizes into discrete levels that contribute to atomic structure and spectroscopy, playing an essential part in both fields. Although both types contribute to the total angular momentum of particles, their origins, quantization principles, and effects vary significantly.

It is vitally important for understanding particle behavior at the quantum level if one wishes to understand magnetic resonance imaging or quantum information science as fields of application.

What is Spin Angular Momentum?

Spin angular momentum (SAM) is an intrinsic property of elementary particles that reflects their rotational angular momentum without physical rotation; rather, it relates to fundamental quantum properties relating to an elementary particle’s internal “spin”. Contrary to popular belief, spin isn’t associated with physical spinning motion but instead is defined by quantum mechanical properties and not associated with actual physical spinning motion.

Spin is quantized, or discrete values exist in terms of quantum behavior. For example, electrons possess half of one Planck constant as spin; thus giving rise to “spin up” and “spin down” states which can coexist – an essential feature of quantum behavior.

Nuclear magnetic resonance imaging (NMR) and magnetic resonance imaging (MRI), however, are harnessing it for medical diagnostic applications as well.

What are the properties of Spin Angular Momentum?

Here are the key properties of spin angular momentum:

  • Intrinsic Property: Spin is an intrinsic property of particles that does not relate to physical movement.
  • Quantized Values: Spin values can be quantized into discrete increments (e.g. +- 1/2h for electrons).
  • Superposition: Particles may exist in various superimposed spin states.
  • Observable Effects: Spin is integral to magnetic properties of particles.
  • Spin Quantum Number (SQN): Particles can be classified by their spin quantum number.
  • Spin Interaction: Spin can interact with external magnetic fields. Spin is central to quantum states and entanglement.
  • Quantum Spin Operators: Spin is associated with quantum mechanical operatorss.
  • Applications and Spintronics: Applications include Spintronics, NMR imaging, and quantum computing.
  • Spin Classification: Is Essential in Particle Physics: Spin classification can assist with understanding particles and their interactions.

What is Orbital Angular Momentum

Orbital angular momentum, also known as the orbital angular momentum represents the product of orbital angular momentum of every electron. Electrons that are free in space transport quantized orbital angular momentum, which can be projected in the direction of the propagation. The orbital angular force typically results in helical wavefronts, or, in a similar way, in a phase proportional to azimuthal angle.

Since angular motion is a vector and is a product of the rotating inertia of the object as well as the velocity of rotation, that’s about a certain direction. To fully define the orbital motion of angular momentum 3D it is necessary to determine the velocity of the motion vector, which sweeps out of the angle, as well as the perpendicular direction to the direction of the angular displacement plane, and the amount of mass which is affected. It is important to know the distribution of masses in space is necessary.

What are the properties of Orbital Angular Momentum?

Here are the key properties of orbital angular momentum:

  • Physical Movement: Orbital angular momentum results from particles’ physical movement along an axis.
  • Quantized Values: Orbital angular momentum values have been quantized into discrete levels.
  • Quantum Numbers: An angular momentum quantum number (l) describes values.
  • Spatial Distribution: Different states possess distinct spatial distributions.
  • Atomic and Molecular Structure: Orbital angular momentum can influence both energy levels and bonding between molecules.
  • Interaction With Spin: The combined effect leads to fine structures and the Zeeman effect.
  • Quantum Mechanical Operator: Orbital angular momentum has its own operators in quantum mechanics.

Key Differences Between Spin and Orbital Angular Momentum

Comparison chart between Spin and Orbital Angular Momentum:

Aspect Spin Angular Momentum Orbital Angular Momentum
Nature Intrinsic property of particles (spinors) The result of the particle’s orbital motion
Origin Independent of the particle’s spatial position Arises due to the particle’s spatial motion
Quantization Quantized in discrete values (e.g., ±½ħ) Quantized into discrete angular levels
Quantum Numbers Spin quantum number (e.g., ±½) Azimuthal quantum number (l)
Observable Effects Contributes to magnetic properties Influences atomic structure, spectroscopy
Superposition Particles can be in spin superposition States can be in an orbital superposition
Interaction with Fields Influences particle behavior in fields This leads to fine structure and the Zeeman effect
Applications Spintronics, quantum information, MRI Chemistry, atomic/molecular structure
Measured in Units Units of reduced Planck constant ħ Units of angular momentum ħ
Basis for Quantum computing, magnetic resonance Spectroscopy, molecular dynamics
Examples Electrons, protons, neutrons Electrons, atoms, molecules
Experimental Techniques Stern-Gerlach experiments, NMR Spectroscopy, diffraction techniques
Interaction with Spin Spin interacts with external magnetic Orbital motion responds to external
fields (spin magnetic moment) fields (magnetic moment due to motion)

Applications of Spin and Orbital Angular Momentum in Technology and Science

Spintronics technology: Utilising spin angular momentum, spintronics facilitates faster, lower energy-consuming electronic devices like magnetic sensors, memory, and logic elements.


  • Quantum Computing: Quantum computers utilize spin and orbital angular momentum as qubits to exponentially speed up complex calculations and transform fields such as cryptography and optimization.
  • Quantum Communication: Quantum states such as spin and orbital angular momentum can facilitate secure quantum communications for unbreakable encryption and data transmission.
  • Medical Imaging: Magnetic resonance imaging (MRI), using spin angular momentum as its foundation, produces noninvasive images of tissues for medical diagnosis and research purposes.
  • Sensors: Spin-based sensors use magnetic field detection technology to measure minute magnetic forces in environments like navigation, geophysics and medical diagnostics.


  • Particle Physics: The spin angle momentum grants clear-sightedness in the identification of particles and classification. It also provides clear-sightedness into the fundamental materials as well in the forces affecting the particles.
  • Physics of Atoms and Molecular Physics: Orbital angular momentum advertises a large influence on the molecular and atomic structure that define energy levels, chemical patterns and spectral patterns.
  • Quantum Information: Angular momentum states facilitate quantum information storage, processing and transmission providing an ideal foundation for quantum cryptography and computing.
  • Emerging Technologies: Nanotechnology advances are driven by angular momentum principles, which enable precise manipulation of nanoparticles for various uses.


Spin angular motion is the rate at which something rotates objects around an axis. Orbital An angular motion or angular force of an orbital refers to the sum of the orbital angular momentum that each electron has. The main difference between orbital and spin angular momentum is that the spin angular motion refers to the angular energy around the central point of the body’s mass. Whereas orbital angular momentum is the angular momentum around an axis that is chosen as the center of rotation.