Can Spins Flip in an EPR Experiment?

[Albex]

hello

I got al little bit confused about spins flipping in an EPR experiment. As far as I know, the idea of EPR is to measure the absorption of an electromagnetic wave induced by spin flips if the energy is conserved by
[tex]\hbar \omega = g_{spin} \mu_B B_0[/tex].
But now I heard several times that a spin cannot be flipped by an electromagnetic dipole field and only optical transitions that include
[tex]\Delta m_s = 0[/tex]
are permitted if there is zeeman splitting.
So how do spins flip then?

Thank you for all answers!

 

[nbo10]

check out Stephen Bundell book, "Magnetism in condensed matter". It has a good discussing on ESR.

 

[charng]

I can provide some clarification on the concept of spins flipping in an EPR experiment. The basic principle of EPR (electron paramagnetic resonance) is to measure the absorption of an electromagnetic wave by a sample with unpaired electrons in a magnetic field. The absorption occurs when the energy of the electromagnetic wave matches the energy difference between two spin states of the unpaired electrons.

In this context, the term "spin flipping" refers to the flipping of the spin of an electron from one state to another. This can happen in two ways - either by applying a magnetic field or by absorbing an electromagnetic wave. In an EPR experiment, the absorption of the electromagnetic wave causes the spins of the unpaired electrons to flip, resulting in a measurable absorption signal.

It is important to note that in EPR, the spin flipping is not caused by an electromagnetic dipole field, but rather by the energy of the electromagnetic wave matching the energy difference between the two spin states. This is why optical transitions, which do not involve a change in the spin state, do not result in spin flipping.

In summary, spins can indeed flip in an EPR experiment, but it is not caused by an electromagnetic dipole field. Instead, it is the result of the energy of the electromagnetic wave matching the energy difference between the two spin states of the unpaired electrons. I hope this helps to clarify any confusion.