Unshifted sine-bell

The size of the window must be carefully fit to the FID being processed. Varian uses the parameter sb to describe the width (in seconds) of the sine-bell window from the 0° point to the 90° point. Thus for an unshifted sine-bell function, we want the 0° to 180° portion of the sine function (2 sb) to just fit over the time duration of the FID at). This is accomplished by setting the value of sb to one-half the acquisition time sb = at/2. Since the sine-bell is not shifted, the sine-bell shift (sbs) is set to zero. For a cosine-bell or 90° shifted sine-bell window, we want the portion of the sine function from 90° to 180° (or sb, since the 0° to 90° portion is of the same duration as the 90° to 180° portion) to just fit over the FID (duration at) sb = at. In addition, the whole sine function is shifted to the left side by the duration of the FID, so we set the parameter sbs (sine-bell shift) equal to —at (left shift corresponds to a negative number). In F we do not have a parameter for acquisition time at) in t, but we know that the maximum t value is just the number of data points times the sampling delay ... 

So you can just set sbl = nilswl and sbsl = —sbl for a 90°-shifted sine-bell, and sbl = nil(2 x swl) and sbsl = 0 for an unshifted sine-bell. Bruker uses the parameter wdw (in both F and To) to set the window function (SINE = sine-bell, QSINE = sine-squared, etc.) and ssb for the sine-bell shift. For example, if ssb = 2, the sine function is shifted 90° (180°/ssb) and we get a simple cosine-bell window. For an unshifted sine-bell, use ssb = 0. 

Figure 5.22. Contour plots of (a) the phase-twist lineshape, (b) the same following magnitude calculation, and (c) the same following resolution enhancement with an unshifted sine-bell window and magnitude calculation.

Figure 6.25. The HMBC long-range correlation spectrum of 6.2 recorded with A = 60 ms and with gradient selection. The sequence used the low-pass J-filter (Section 6.4.1) to attenuate breakthrough from one-bond correlations (which appear with Jch doublet structure along fj (arrowed)). IK ta data points were collected for 256 ti increments of 8 transients each and the data processed with unshifted sine-bells in both dimensions, followed by magnitude calculation. After zero-filling once in ti the digital resolution was 4 and 80 Hz/pt in f2 and fi respectively.

Figure 7.11. (a) The 500 MHz proton homonuclear J-resolved spectrum of 7.4 (after tilting and symmetrisation). The f2 projection (b) approximates to the proton-decoupled proton spectrum and is considerably less complex than the conventional ID spectrum (c). 4K t2 data points were acquired for 64 ti increments over spectral widths of 5 ppm and 60 Hz respectively. The final fi resolution after zero-filling was 0.5 Hz/pt. Data were processed with unshifted sine-bell windows in both dimensions and are presented in magnitude mode. 

FID of row 71 and unshifted, Sine-Bell FID of row 71 and 7r/2-shifted, Sine-Bell squared window function squared window function... 

COSY (HETCOR) spectoim (500 MHz) of die palladium complex 6.10. 2 K data points were collected for 256ti increments of 128 ttansients each for a 40 x 2.6-ppm window. Unshifted sine bells were applied in both dimensions and after zero filling once in each, die digital resolution was 2.5 and 5.0Hz/pt in/2 and/i, respectively. 

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