Preparing for Acquisition, Frequency Related Parameters
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6 Preparing for Acquisition,
Frequency Related Parameters
This chapter will explain two of the most important parameters for observing a NMR
spectrum. Before assigning values to various parameters, it is important that the user
understands the concept of data sets, as groups of parameters are inextricably linked to
these.
6.1 Frequency
The frequencies of the transmitted signals on channels one, two and three etc. are given by
SFO1, SFO2 and SFO3, etc., respectively. However, these frequencies may not be set
directly (you will notice that they cannot be highlighted using the mouse).
The transmitted frequencies are controlled by setting offsets to basic frequencies BF1, BF2
and BF3 etc.
For the observe channel:
• SFO1 = BF + offset (O1)
Transmitted frequency is automatically set by the user.
Similarly, for the next two decoupling channels:
• SFO2 = BF2 + offset (O2)
• SFO3 = BF3 + offset (O3)
When a specific nucleus is selected, the appropriate basic frequency is automatically set.
After reading a standard parameter set, the basic frequency will be set correctly and only the
offset values need to be adjusted.
Remember that SFOX is the most relevant parameter in that it is the frequency that is
actually transmitted to the sample. Note also that the offsets can be set to zero in which case
SFOX = BFX. A more detailed description is given in the next section.
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