As it represents a probability Pk (t) is dimensionless (Exercise 2.5). In (2.16) θ is the angle between the vectors μ and E0. It is clear that the squared matrix element
As it represents a probability Pk (t) is dimensionless (Exercise 2.5). In (2.16) θ is the angle between the vectors μ and E0. It is clear that the squared matrix element