0 Hi, I am trying to run a wet sequence but I'm having trouble getting good results on a sample with 90:10 water:methanolD3. O1 is well calibrated as are the 4 selective pulses (I tried both sinc1.100 and Gaus90.1000 shapes) and the gradients. The result is as awful as running a normal proton. In the parameters there are two types of parameters I haven't touched because I don't understand what they do or how they should be calibrated: something called SPOAL (phase alignment of frequency offset) SPOFF (offset frequency) for each of the selective pulses. I would appreciate any kind of help here. asked Nov 21 '14 at 00:20 gravatar 83

 0 SPOFF it's a value that comes from difference in offsets. If you want to apply selective shaped pulse at the spectra offset (o1p) just leave SPOFF 0. On the other hand if you want to excite another region of spectrum (not in frequency offset - o1p) you must calculate SPOFF for each shaped pulse (for example pulse1 has SPOFF1, etc.). How to calculate it ? If your region of interest lies on the left from the offset just substract it's frequency from offset (one must do the calculations in Hz; SPOFF should be also enter in Hz not ppms !), value of SPOFF will be positive. In case of right sided region of o1p, final SPOFFS value will be negative, calcluations look the same as in a case of left side of spectrum. SPOAL is a mystery for me. I have never touched it during my work with seletive pulses, so I can't help you. All I can do is quote some piece from Bruker pulse programming manual: ``````Phase alignment Shapes with frequency offsets do vary the phase in order to efficiate the frequency shift. By this variation the total phase of the shape is affected as well. The parameter SPOAL[0..31] determines whether the phase is aligned relative to the start or the end of the pulse. SPOAL has a range of 0 to 1. If SPOAL = 0, the relative phase shift is 0 at the beginning of the pulse whereas it is determined by the frequency offset SPOFFS and the pulse length at the end of the pulse. If SPOAL = 1 the relative phase shift is 0 at the end of the pulse. `````` If you did not calibrate SPOFF, all selective pulses were "hitting" precisely in frequency offset (o1p or o1). answered Nov 21 '14 at 01:46

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Asked: Nov 21 '14 at 00:20

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Last updated: Dec 05 '14 at 10:35