For 10 points, name this rotational analogue of linear momentum.
Leslie Allen showed that Laguerre-Gaussian laser modes have well-defined values of this quantity using the fact that its time-averaged density is the cross product of axial radius with the Poynting vector. That result helped define its "optical" form, and the interaction of two varieties of this quantity in an atom is termed Russell-Saunders coupling. When this quantity is coupled with spin, (*) Clebsch-Gordan coefficients are used to describe eigenstates, and the eigenfunctions of its associated operator are the spherical harmonics. The eigenvalues of the associated operator are h-bar times the square root of azimuthal quantum number L times the quantity L plus one, meaning this quantity is quantized in units of h-bar. Classically, this quantity's time derivative is torque and it can be found by multiplying the moment of inertia by the angular velocity. For 10 points, name this rotational analogue of linear momentum.
Leslie Allen showed that Laguerre-Gaussian laser modes have well-defined values of this quantity using the fact that its time-averaged density is the cross product of axial radius with the Poynting vector.
angular momentum [do not accept linear momentum]