Estimates the rotational correlation time from the longitudinal CSA relaxation rate.
This function solves the Redfield relaxation theory (rotationally modulated CSA induced longitudinal relaxation) expression back for the rotational correlation time. Make sure your CSA is in fractions, not ppm.
R1 - longitudinal relaxation rate, Hz del_sq - second rank invariant of the CSA, see blinv.m function B0 - magnetic field, Tesla isotope - isotope specification string, e.g. '1H'
tauc - rotational correlation time, seconds
Most relaxation rates are not solely due to CSA, and so the result is an estimate. If you get the "no real solutions" error, you relaxation is certainly not CSA dominated.
Version 2.1, authors: Ilya Kuprov