# Orbital Angular Momentum: Need at least 2 particles?

• LarryS
In summary, the definition of orbital angular momentum is rxp, which means that one particle can possess orbital angular momentum about the origin. However, it is difficult to find examples in nature where a system of one particle has orbital angular momentum, as it is more convenient to consider the origin of the reference frame at the position of the particle. This is not possible for systems with two or more particles, where the angular momentum is absolute.
LarryS
Gold Member
The definition of orbital angular momentum, whether for classical mechanics or for quantum mechanical operators, is rxp. Technically, according to this definition, one particle can possesses orbital angular momentum - in this case about the origin.

But I cannot think of any examples, in classical or quantum mechanics, in nature in which a system of one particle has orbital angular momentum. It seems like a minimum of 2 "particles" is necessary.

Every system of one particle has "orbital" angular momentum - in some frames.
It's just pointless to consider those reference frames if you really just have one particle. It is much more convenient to put the origin of your reference frame where the particle is.

bhobba
mfb said:
Every system of one particle has "orbital" angular momentum - in some frames.
It's just pointless to consider those reference frames if you really just have one particle. It is much more convenient to put the origin of your reference frame where the particle is.

Makes sense. If one has a system of just 1 particle, then you can make the system's angular momentum "go away" by moving the origin of the reference frame to the position of the particle. But, obviously, you cannot do that if the system contains 2 or more particles. It's like those system's angular momentum are "absolute".

## 1. What is Orbital Angular Momentum?

Orbital Angular Momentum (OAM) is a property of a particle or system of particles that describes the rotational motion of the particles around a central point or axis. It is a vector quantity that is dependent on the position and velocity of the particles.

## 2. How is Orbital Angular Momentum different from Spin Angular Momentum?

While both Orbital Angular Momentum and Spin Angular Momentum are types of angular momentum, they differ in their physical origins. Orbital Angular Momentum is due to the motion of particles around a central point, while Spin Angular Momentum is an intrinsic property of particles related to their spin.

## 3. How is Orbital Angular Momentum quantized?

The quantization of Orbital Angular Momentum is a consequence of the wave-like nature of particles. The allowed values of OAM are integer multiples of a fundamental unit known as Planck's constant divided by 2π.

## 4. Can Orbital Angular Momentum be transferred between particles?

Yes, Orbital Angular Momentum can be transferred between particles through interactions such as collisions or electromagnetic forces. This transfer can result in changes in the particles' orbits and velocities.

## 5. What are some applications of Orbital Angular Momentum in science and technology?

Orbital Angular Momentum has applications in various fields such as quantum mechanics, optics, and telecommunications. It is used in the development of quantum computers, high-capacity optical communication systems, and even in the study of the rotation of galaxies and other celestial bodies.

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