The following parameters can be examined and/or changed from the View/Spectral Parameters menu or by typing the 2-letter names. In both cases, a dialog box appears displaying the chosen parameter and related parameters. Many of these parameters are printed on plots. The NUTS data translation attempts to translate and insert into the NUTS file header as many parameters from the original file as possible. Some parameters refer to the total data set, such as Date and Number of scans. For others, two sets of parameters are listed for the two dimensions, such as Spectrometer Frequency and Sweep Width.
- CO Comment (eg., sample name or number).
UID Unique identifier
DA Date of data acquisition.
EX Name of pulse experiment used to acquire data.
F1, F2 Spectrometer frequencies in the first and second dimensions.
NA Number of scans acquired.
O1, O2 Spectrum offsets in the first and second dimensions.
PD Pulse delay used in data acquisition.
PW Pulse width used in data acquisition.
SF Spectrometer Frequency.
SW Sweep width in Hz.
US User name or initials
W1, W2 Sweep width in the first and second dimensions.
Entering this command with no subsequent argument returns the current solvent. In the non-2-letter command mode, it allows the solvent to be set. For example,
sets the solvent parameter to DMSO-d6.
Each of these values is the difference, in Hz, between the center of the spectrum and 0 ppm. This is how NUTS keeps track of the chemical shift scale. For 1D data, normally, the chemical shift reference is set using the cursor or, for TMS, the SZ command. However, offset values may be entered directly. For 2D data, the cursor can be used to set the shift reference; see details.
Number of points
The number of points in the data set, listed for both dimensions.
This is calculated from the sweep width.
This is calculated from the sweep width and the number of data points.
NUTS must keep track of whether the data is an FID (Time domain) or a spectrum (Frequency domain). Occasionally, NUTS fails to correctly identify when the data represent an FID or a spectrum, and this can be corrected by entering the appropriate word in the Domain box. Save the change by executing a UH (update header) command.
There are 3 possible values for this parameter: Complex, Real and TPPI. The latter is used to indicate that the data were acquired using Bruker’s sequential acquisition, and for 2D data which was acquired using TPPI in the indirect dimension.
Keep in mind that NUTS will label the dimensions as 1 and 2, with 1 always being the dimension that is currently displayed horizontally. So when you are viewing, for example, a HETCOR spectrum from a 300 MHz instrument, with the carbon dimension displayed horizontally, that is dimension 1. So F1 (SF for dimension 1) will be 75 MHz. When you do a TD, the 1H dimension is now horizontal, so dimension 1 is 1H, and F1 is now 300 MHz.
It’s easiest to ignore 1 and 2, and just look at the parameters window, keeping in mind that the left column of parameters applies to the dimension that you have displayed horizontally and the right column applies to the vertical dimension.
Note that a common practice is to label the indirect dimension as "1" (even though it’s the secondary dimension, and is processed second) because the corresponding t1 period in the pulse sequence (the incremented time variable) occurs before the acquisition time. To avoid confusion, the NUTS documentation uses the terms direct and indirect to refer to the different dimensions, which is unambiguous.
If considering only 1D data, the parameters can have the obvious names SF, SW and OF. But with 2 dimensions, we need to add labels 1 and 2. But in Nuts, everything is 2 letters. So these parameters became:
SF ==> F1 and F2
SW ==> W1 and W2
OF ==> O1 and O2 (NOT to be confused with Bruker’s O1 and O2, which are defined differently!)
The NUTS offset is defined as the number of Hz between the center of the spectrum and 0 ppm. This is the parameter that keeps track of the chemical shift referencing.
Last updated: 4/6/05