Estimate the spin-lattice relaxation time constant based on the following plot of Mz(t).

The data appears to have the functional form:
Mz = Mo
( 1 - 2e-t/T1 )
If we set Mz = 0, and solve for T1 when we have:
0 = Mo ( 1 - 2e-t/T1 )
1=2e-t/T1
ln(1/2) = -t/T1
T1 = -t/ln(1/2)
Setting t = 2 seconds, we obtain T1 = 2.9 seconds.