16

where M_pg in the matrix element of the rotating component
of the total magnetic moment between the states p & q.
The absorbed power P(ν) is obtained by subtracting from (2.26)
the transitions from q to p, multiplied by the involved energy
hν & running over a small frequency interval 2Δν around ν.
For we can write

with

Introducing the absorption coefficient & the
density fⁿ of the magnetic moment

we find

continued p. 22