Frequency lists

Frequency lists are used in NMR experiments to specify arrays of frequencies for selective excitation, CEST, or other variable-frequency experiments. On Bruker spectrometers, these are stored in files like fq1list through fq8list.

NMRTools represents frequency lists as FQList structures that preserve encoding information (Hz vs ppm, relative vs absolute) and provide safe conversion functions.

Accessing frequency lists

Frequency lists are automatically imported when loading data:

# Load CEST experiment
spec = loadnmr("path/to/cest/experiment")

# Get frequency list
fqlist = acqus(spec, :fq1list)

Extracting frequency values

Use ppm() and hz() to safely extract frequency values. These functions handle all unit conversions automatically.

Get chemical shifts (in ppm)

dim = dims(spec, F2Dim)
ppm_values = ppm(fqlist, dim)

Get offsets from carrier (in Hz)

dim = dims(spec, F2Dim)
offset_hz = hz(fqlist, dim)

Creating frequency lists

Construct FQList objects programmatically:

using NMRTools

# Frequency list in Hz, relative to carrier
fq_rel = FQList([100.0, 200.0, 300.0], :Hz, true)

# Frequency list in ppm, absolute (chemical shifts)
fq_abs = FQList([7.5, 8.0, 8.5], :ppm, false)

FQList{Float64}([7.5, 8.0, 8.5], :ppm, false)