Operating on spin angular momenta

[runninglow]

how am i supposed to carry out say, a lowering operation?for example:S_(upward spin & upward spin) or S_(downward spin & upward spin). and raising or lowering a combination of spin,what do they mean anyway?i want the physical feel of the situation.

 

[malawi_glenn]

raising and lowering of spin and angular momenta should be quite intuitive I guess, that it is an operation which increases or decreases the projection of a certain angular momentum about a fixed axis (the standard in almost all quantum mechanics is that one has the Z-axis as reference).

The length of the angular momentum vector is always fixed, and due to quantum mechanics, only certain projections on axes are possible (c.f with a "classical" vector which can have a continuous setup of projections)

A rasing, or lowering, operation just changes that projection, but of course by a disctrete amount.

If you want, provide a specific situation where you have trouble, and we'll try to help you.