Question

a)In a magnetic field, the Larmor frequency of ¹H nuclei is 63.87 MHz and the gyromagnetic ratio of ¹H is given as 42.58 MHzT^-1. Calculate the magnetic field B in units of T.

b)By using the gyromagnetic ratio given in the table, calculate the Larmor frequencies of ¹H and ²³Na in a magnetic field of 3.0 T. And compare your result to a.

Nucleus	Gyromagnetic ratio (γ) in MHz/T
1H	42.58
23Na	11.26

c)The Larmor frequency of an unknown nucleus detected in an NMR specroscopy (at B = 1.205 T) was 7.8764 MHz. Identify the unknown nucleus.

Answer 1

1) When placed in a magnetic field, charged particles will precess about the magnetic field. In NMR, the charged nucleus, will then exhibit precessional motion at a characterisitc frequency known as the Larmor Frequency.

which is given by

where gamma is gyromegnetic ratio and B is applied magnetic field

so Magnetic field

plug in values

2) from the same formula we calculate larmour frequancy of H

and of Na

3) gyromgnetic ratio of unknown nuclei

which is from the table we see is Deutirium 2H Nuclei