r4187 - /branches/N_state_model/generic_fns/align_tensor.py -- December 11, 2007 - 17:26

Author: bugman
Date: Tue Dec 11 17:26:56 2007
New Revision: 4187

URL: http://svn.gna.org/viewcvs/relax?rev=4187&view=rev
Log:
Implemented the generic_fns.align_tensor.kappa() function.


Modified:
    branches/N_state_model/generic_fns/align_tensor.py

Modified: branches/N_state_model/generic_fns/align_tensor.py
URL: 
http://svn.gna.org/viewcvs/relax/branches/N_state_model/generic_fns/align_tensor.py?rev=4187&r1=4186&r2=4187&view=diff
==============================================================================
--- branches/N_state_model/generic_fns/align_tensor.py (original)
+++ branches/N_state_model/generic_fns/align_tensor.py Tue Dec 11 17:26:56 
2007
@@ -30,6 +30,7 @@
 from angles import wrap_angles
 from data import Data as relax_data_store
 from data.align_tensor import AlignTensorData
+from physical_constants import gC, gH, gN, gO, gP, h_bar, mu0
 import pipes
 from relax_errors import RelaxError, RelaxNoPipeError, RelaxNoTensorError, 
RelaxStrError, RelaxTensorError, RelaxUnknownParamCombError, 
RelaxUnknownParamError
 
@@ -488,6 +489,52 @@
         return [0, 2*pi]
 
 
+def kappa(nuc1='N', nuc2='H'):
+    """Function for calculating the kappa constant.
+
+    The kappa constant is
+
+        kappa = -3/(8pi^2).gI.gS.mu0.h_bar,
+
+    where gI and gS are the gyromagnetic ratios of the I and S spins, mu0 is 
the permeability of
+    free space, and h_bar is Planck's constant divided by 2pi.
+
+    @param nuc1:    The first nucleus type.
+    @type nuc1:     str
+    @param nuc2:    The first nucleus type.
+    @type nuc2:     str
+    @return:        The kappa constant value.
+    @return type:   float
+    """
+
+    # Gyromagnetic ratio of the first nucleus.
+    if nuc1 == 'C':
+        gI = gC
+    elif nuc1 == 'H':
+        gI = gH
+    elif nuc1 == 'N':
+        gI = gN
+    elif nuc1 == 'O':
+        gI = gO
+    elif nuc1 == 'P':
+        gI = gP
+
+    # Gyromagnetic ratio of the second nucleus.
+    if nuc2 == 'C':
+        gS = gC
+    elif nuc2 == 'H':
+        gS = gH
+    elif nuc2 == 'N':
+        gS = gN
+    elif nuc2 == 'O':
+        gS = gO
+    elif nuc2 == 'P':
+        gS = gP
+
+    # Kappa.
+    return -3.0/(8.0*pi**2) * gI * gS * mu0 * h_bar
+
+
 def map_labels(index, params, bounds, swap, inc):
     """Function for creating labels, tick locations, and tick values for an 
OpenDX map.