文档介绍：Lecture Notes: ic Resonance Spectroscopy
In our discussion of spectroscopy, we have shown that absorption of .
radiation occurs on resonance: When the frequency of applied . field matches the
energy splitting between two quantum states.
ic resonance differs from these other methods in the sense that we need to
immerse the same in a ic field in order to see the levels that we probe with an
external (rf or µwave) field. (Two fields: Static ic and .)
We will be probing the energy levels associated with the spin angular momentum
of nuclei and electrons: NMR--nuclear ic resonance and ESR/EPR--electron spin
resonance.
Angular momentum:
In our treatment of rotational energy levels, we said that the energy levels
depended on the rotational angular momentum, L , which was quantized:
L2 =
2J (J + 1) J = 0,1,2… rot . quant. number
• Degeneracy of J was (mJ = 0, …, ± J) →(2 J + 1)
• We related L2 to the energy levels
L2
E = ∝ BJ (J + 1)
rot 2I
Actually, all angular momentum is quantized.
If a particle can spin, it has . and quantized E levels.
In particular, we also have to be concerned with the spin of individual nuclei and
electrons.
Lecture Notes: ic Resonance Spectroscopy Page 1
You already know that electrons have…
ORBITAL angular momentum
M2 =
2 (
+ 1)

= 0,1,2… orbital angular momen