The Chemistry and Life box in Section described the techniques called NMR and MRI. (a) Instruments for obtaining MRI data are typically labeled with a frequency, such as 600 MHz. Why do you suppose this label is relevant to the experiment? (b) What is the value of ΔE in Figure that would correspond to the absorption of a photon of radiation with frequency 450 MHz?
▲ Figure Nuclear spin. Like electron spin, nuclear spin generates a small magnetic field and has two allowed values. (a) In the absence of an external magnetic field, the two spin states have the same energy. (b) When an external magnetic field is applied, the spin state in which the spin direction is parallel to the direction of the external field is lower in energy than the spin state in which the spin direction is antiparallel to the field direction. The energy difference, ΔE, is in the radio frequency portion of the electromagnetic spectrum.
(c) In general, the stronger the magnetic field, the greater the information obtained from an NMR or MRI experiment. Why do you suppose this is the case?
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