# Determining the value of B1 (or RF) in NMR

by Bubble22
Tags: determining
 Sci Advisor PF Gold P: 2,082 You wrote down the frequency of precession (from the z axis to -z and back to +z) in terms of B1. Now write the frequency in terms of period (time) $f_1=1 / t_1$ for one cycle. What fraction of one cycle is the journey from the z axis to the xy plane?
 Quote by marcusl You wrote down the frequency of precession (from the z axis to -z and back to +z) in terms of B1. Now write the frequency in terms of period (time) $f_1=1 / t_1$ for one cycle. What fraction of one cycle is the journey from the z axis to the xy plane?
 Sci Advisor PF Gold P: 2,082 Determining the value of B1 (or RF) in NMR You now have $t_1(360)$ in terms of B1. I've written it with the argument 360 because this period is the length of time for the spin to precess from the z direction down to the xy plane, on to -z, back to the xy plane, and back up to z, for a total angle of 360 degrees. You want the time it takes to go from z to the xy plane, which is an angle of 90 deg. You have everything needed to find that value.