BCMB/CHEM 8190
PROBLEM SET 4
1) Use density matrix methods to examine magnetization for a pair of spin 1/2 nuclei in a
magnetic field Bo along the z axis. The first spin listed oscillates at ωA and the second
at ωX. Assume the scalar coupling is small and can be neglected.
a). Show the elements of an equilibrium density matrix (sigma) in the simple product
basis set basis set.
b). Calculate equilibrium z magnetization using matrix methods.
c). Find the frequency at which the 1,4 element oscillates.
2) a) In product operator notation, show the effect of a short
(hits both spins) 90 degree RF pulse about the + y axis on the density matrix
represented by the I1xI2z product operator.
b) Show the density matrix equivalent (fill in elements of matrix) of the result in a
two
spin 1/2 system and sketch the spectrum that would result
from observing x magnetization.
3) Using product operators for a pair of spin 1/2 nuclei (I and S)
identify the operators evolving during t1 that are
detectable during t2 as I spin magnetization. The two spins
are scalar coupled with value J and t is set to 1/(4J).
I----90x--t--180x--t--90x-------------- Acquire
S------------180x-----90y-----t1-----90y---t2---