Electrons polarized along the x-direction are in a magnetic field B1î + B2(ĵ cos ωt + k̂ sin ωt), where B1 >> B2 and ω are positive constants. The value of ℏω for which the polarization-flip process is a resonant one, is
1
2μB|B2|
2
μB|B1|
3
μB|B2|
4
2μB|B1|