2D Exchange Spectra of Solids

Reference: J.Magn.Reson, 79, 269-290 (1988)

This is a hypercomplex experiment in which the 2 halves of the data are scaled differently.  See description of noesy processing for detailed description of hypercomplex data and how to process it in NUTS.

After the first dimension FT, the real half of each odd-numbered slice is combined with the real half of the following even-numbered slice, but the even numbered slices must first be scaled by a factor of -0.3.  Except for this scaling, processing is essentially the same as other hypercomplex experiments.

Because the NUTS Arrayed Mode applies the same processing to all slices, Arrayed Mode cannot be used in processing this data.

The scaling is most simply accomplished by placing the data to be scaled into the add/subtract buffer with an appropriate factor, then adding the buffer to the current data.  

To accomplish a scaling factor of -0.3, the multiplier (AM) is set to -1.3, and then the buffer is added to the current data ( -1.3 + 1 = -.3 )   This is accomplished in a Link with the   al as   commands.  AL loads the buffer, using the value of AM as a multiplier, and AS adds the buffer to the data.

The Link for processing in the first dimension is:

ga ls ls ls ls bc em ft ps bc tr ia          ga ls ls ls ls bc em ft ps al as bc tr st in

Each cycle through the Link processes a pair of slices.  Four left shifts (LS) are performed before the FT, because this is an echo experiment and data acquisition starts a bit before the echo.  

The complete macro is shown here.  Before beginning, open the data, set LB, FT and phase the first slice.  At the end of the macro, phasing must be done in the indirect dimension.  See phasing 2D data for description.

NutsMacro 2dexch
ask filea
set filec ft1.2d
set am -1.3
ga bc ls ls ls ls em ft ps bc tr ia ga bc ls ls ls ls em ft ps al as bc tr st in

; reset file names and transpose data
set filea ft1.2d
set sl 1
ga
set filec td.2d
td

; reset file names and process 2nd dimension
set filea td.2d
set sl 1
ga
set filec ft2.2d
ga bc em ft sc in

; read in final data set and display stacked plot
set filea ft2.2d
set sl 1
ga
ss 
sp
end

This is illustrated using a ²H spectrum of d₆-dimethylsulfone (courtesy of Dr. Detlef Reichert, University of Halle, Germany).

For this spectrum, the direct dimension was processed using 100 Hz linebroadening and zero-order phase correction of 247.5 degrees.   Phase correction in the indirect dimension was zero-order =  -45.3 and 1st order = 89.2

Note the low-intensity, elliptical exchange features.   Dr. Reichert points out that ideally, the scaling eliminates the anti-diagonal, but some anti-diagonal remains, due to the anisotropy of the relaxation times T1Z and T1Q, preventing complete cancellation of the mirror images. 

Last updated: 12/4/00