Author: tlinnet
Date: Mon Jul 28 12:56:51 2014
New Revision: 24780
URL: http://svn.gna.org/viewcvs/relax?rev=24780&view=rev
Log:
Added function to calculate rotating frame paramters for lib/nmr.py.
This function is called several times in
specific_analyses/relax_disp/data.py by plotting functions.
sr #3124(https://gna.org/support/?3124): Grace graphs production for R1rho
analysis with R2_eff as function of Omega_eff.
sr #3138(https://gna.org/support/?3138): Interpolating theta through
spin-lock offset [Omega], rather than spin-lock field strength [w1].
Modified:
branches/r1rho_plotting/lib/nmr.py
Modified: branches/r1rho_plotting/lib/nmr.py
URL:
http://svn.gna.org/viewcvs/relax/branches/r1rho_plotting/lib/nmr.py?rev=24780&r1=24779&r2=24780&view=diff
==============================================================================
--- branches/r1rho_plotting/lib/nmr.py (original)
+++ branches/r1rho_plotting/lib/nmr.py Mon Jul 28 12:56:51 2014
@@ -23,7 +23,7 @@
"""Module containing functions related to basic NMR concepts."""
# Python module imports.
-from math import pi
+from math import atan2, pi, sqrt
# relax module imports.
from lib.physical_constants import g1H, return_gyromagnetic_ratio
@@ -95,3 +95,35 @@
# Convert and return.
return frq * 2.0 * pi * B0 / g1H * return_gyromagnetic_ratio(isotope)
* 1e-6
+
+
+def rotating_frame_params(chemical_shift=None, spin_lock_offset=None,
omega1=None):
+ """Calculate the rotating frame paramaters.
+
+ @keyword chemical_shift: The chemical shift in rad/s.
+ @type chemical_shift: float
+ @keyword spin_lock_offset: spin-lock offset in rad/s.
+ @type spin_lock_offset: float
+ @keyword omega1: Spin-lock field strength in rad/s.
+ @type omega1: float
+ @return: The average resonance offset in the
rotating frame, angle describing the tilted rotating frame relative to the
laboratory, effective field in rotating frame.
+ @rtype: float, float, float
+ """
+
+ # The average resonance offset in the rotating frame.
+ Delta_omega = chemical_shift - spin_lock_offset
+
+ # Calculate the theta angle describing the tilted rotating frame
relative to the laboratory.
+ # theta = atan(omega1 / Delta_omega).
+ # If Delta_omega is negative, there follow the symmetry of atan, that
atan(-x) = - atan(x).
+ # Then it should be: theta = pi + atan(-x) = pi - atan(x) = pi -
abs(atan( +/- x)).
+ # This is taken care of with the atan2(y, x) function, which return
atan(y / x), in radians, and the result is between -pi and pi.
+ if Delta_omega == 0.0:
+ theta = pi / 2.0
+ else:
+ theta = atan2(omega1, Delta_omega)
+
+ # Calculate effective field in rotating frame.
+ w_eff = sqrt( Delta_omega*Delta_omega + omega1*omega1 )
+
+ return Delta_omega, theta, w_eff
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Re: r24780 - /branches/r1rho_plotting/lib/nmr.py