How to fit an Heteronuclear Correlation spectrum
Example :
31P/1H Heteronuclear Correlation
By "hetero-nuclear correlation" we assume that the two
dimensions (F1 & F2) of the spectrum have different characteristics.
Basic principles ...
-
in an heteronucelar correlation you can toggle
between the two dimensions by transposing the 2D dataset (button in the left
bar or in the bottom fit parameters, or [Menu,2D,TranposeRR].
-
be carefull that the saved parameters do not
account for the transposition, your spectrum has to be in the same state
when reloading the fit parameters.
-
only the parameters of the actual horizontal
dimension (F2) can be modified in the fit parameters edition tools.
-
when dealing with quadrupoles, only the horizontal
dimension can compute second order effects.
The basic different steps for initializing :
-
create a fit of the
F2 dimension or reload the fit of the corresponding 1D spectrum
-
transpose and do the
same in the second dimension (F1)
-
switch to the 2D
fitting mode (listbox in the left panel, enlarge the window if you don't see
it).
-
click the Crosspeaks
box (left pannel) and switch to the heteromode. (The dialog box should
display all possible cross peaks)
-
click Init from 1D
to create dummy intensity values
-
zero the unexpected
cross peaks
-
return from dialog and click the compute button to
update the graph. You should have a 2D fit supperimposed to the experimental
spectrum.
Description of the procedure...
Step 1 : Fit of a 1D spectrum containing all the
peaks that will be present in each of the dimensions of the 2D spectrum.
This step is
not necessary but can simplify the process of fitting the 2D dataset.
If you need
you can learn more about fitting a 1D spectrum with
Gaussian/Lorentzian lines.
Step 2 : Switch to the 2D dataset.
Having the 1D
spectrum and fit loaded, just go the the [Menu/File/Open] and open the 2D
dataset (*.rr files for Bruker).
or
Load in the 2D dataset [Menu/File/Open] and open the 2D dataset (*.rr files for
Bruker) and load the 1D fit parameters [Menu/Decomposition/Load Other]
Step 3 : Switch the decomposition mode from 1D to
2D
In the lef
panel, change the fitting mode from "Fit 1D" to "Fit 2D" (if you do not see this
option, enlarge the dmfit window to make it appear).
Step 4 : Call the Cross Peaks dialog box and set
values
-
Call the
"Cross Peaks dialog box" by clicking the button that appeared in the left panel.
-
If the button
at the top of the window is labeled "Auto" you will fit an homonuclear
correlation, click it to switch to "Hetero" hetero-correlation mode.
-
Click on "Init
from 1D" to set default values or enter the values you want in the different
cross peaks intensities
-
Click Ok to
get back to the main window
Remark : all no zero values for cross-peak
intensities will be optimised in the fitting process, future development should
allow fixing or freing all the individual lines. The display of the Cross-Peak
dialog is rather crowded, it can handle up to 50 lines and 2500 cross-peaks.
Step 5 : Loading the second dimension parameters
description to come
Step 6 : Optimising the intensities of cross-peaks
-
Same rules
apply for fitting 2D experiments and 1D experiment except that the 1D Amplitude
is not taken into account. All boldface paramters will be optimised. Be
carefull that this could lead to lengthy computations and minimise the number of
free parameters if you can.
-
Click
the [Optimize] button to
optimize the current solution (all boldface parameters will be adjusted
as well as the non zero cross-peaks)
-
Click on "Init
from 1D" to set default values or enter the values you want in the different
cross peaks intensities
-
Click Ok to
get back to the main window
Step 7 : Reporting and Saving
Fit parameters can be saved in machine readable binary
format [Menu/Decomposition/Save Fit] or [Menu/Decomposition/Save as Fit] and
thus retrieved later exactly in same state.
Parameters can be reported in human readable format by clicking
the [Report] button to report the current line
paramters in a dialog box from which you can Select/Copy and further Paste word
processing or SpreadSheet programs.