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These commutation relations are relevant for measurement and uncertainty, as discussed further below. In molecules the total angular momentum F is the sum of the rovibronic (orbital) angular momentum N, the electron spin angular momentum S, and the nuclear spin angular momentum I.
The gauge-invariant angular momentum (or "kinetic angular momentum") is given by = (), which has the commutation relations [,] = (+ ()) where = is the magnetic field. The inequivalence of these two formulations shows up in the Zeeman effect and the Aharonov–Bohm effect .
The commutation relation between the cartesian components of any angular momentum operator is given by [,] =, where ε ijk is the Levi-Civita symbol, and each of i, j and k can take any of the values x, y and z.
The angular momentum of m is proportional to the perpendicular component v ⊥ of the velocity, or equivalently, to the perpendicular distance r ⊥ from the origin. Angular momentum is a vector quantity (more precisely, a pseudovector) that represents the product of a body's rotational inertia and rotational velocity (in radians/sec) about a ...
The total angular momentum operators can be shown to satisfy the very same commutation relations, [,] = , where k, l, m ∈ {x, y, z}. Indeed, the preceding construction is the standard method [ 4 ] for constructing an action of a Lie algebra on a tensor product representation.
The Wigner D-matrix is a unitary matrix in an irreducible representation of the groups SU (2) and SO (3). It was introduced in 1927 by Eugene Wigner, and plays a fundamental role in the quantum mechanical theory of angular momentum. The complex conjugate of the D-matrix is an eigenfunction of the Hamiltonian of spherical and symmetric rigid rotors.
Examples of vector operators are the momentum, the position, the orbital angular momentum, , and the spin angular momentum, . (Fine print: Angular momentum is a vector as far as rotations are concerned, but unlike position or momentum it does not change sign under space inversion, and when one wishes to provide this information, it is said to ...
In quantum mechanics, the momentum operator is the operator associated with the linear momentum. The momentum operator is, in the position representation, an example of a differential operator. For the case of one particle in one spatial dimension, the definition is: where ħ is the reduced Planck constant, i the imaginary unit, x is the ...