Relax disp.spin lock offset+field

Setting up relax_disp.spin_lock_offset and relax_disp.spin_lock_field

Refer to the manual for parameter explanation

This page is a little help to understand how to use the functions:

1. relax_disp.spin_lock_offset()
2. relax_disp.spin_lock_field()

spin lock offset

Manual on relax_disp.spin_lock_offset
The relax function relax_disp.spin_lock_offset() requires the values to be provided in ppm.

relax_disp.spin_lock_offset(spectrum_id=None, offset=None)

spin lock field

Manual on relax_disp.spin_lock_field
The relax function relax_disp.spin_lock_field() requires the values to be provided in Hz.

relax_disp.spin_lock_field(spectrum_id=None, field=None)

Literature comments

See Figure 1 and 10 in the reference.

Palmer, A.G. & Massi, F. (2006). Characterization of the dynamics of biomacromolecules using rotating-frame spin relaxation NMR spectroscopy. Chem. Rev. 106, 1700-1719 DOI

Try to reproduce Figure 1.

Figure produced with script found here.

spin lock offset

The offset is in the literature noted as $\Omega$, where $\Omega$ is the $^{15}$N resonance offset from the spin-lock carrier.

In the literature, the values are often stated as "offset", "carrier offset", "offset of the spin-lock pulse" with values given in Hz, and have values from 0-500 to 10-20.000 Hz.

Relax needs input in ppm, and converts to the rad/s, with the following function calls.

offsets[ei][si][mi][oi] = frequency_to_rad_per_s(frq=cdp.spin_lock_offset[id], B0=frq, isotope=spin.isotope)
"""Convert the given frequency from ppm to rad/s units."""
return frq * 2.0 * pi * B0 / g1H * return_gyromagnetic_ratio(isotope) * 1e-6

spin lock field

The spin lock field strength is noted $\nu_1$.
The Chemical Shifts $\delta$ in ppm for nuclei of interest (ex. $^{15}$N and which have been loaded in with relax function chemical_shift_read from a peak list formatted file)

The trouble

The trouble is.

Does the Hz frequency refers to RF fields applied at the 1H Larmor frequency or 15N frequency?

At page 1708 is states that w_1S = w_1 and w_eS = w_e. And in pulse sequence it states that:

Code reference calculations in relax

The code which is called resides in:

lib/nmr.py

frequency_to_rad_per_s(frq=None, B0=None, isotope=None):

specific_analyses/relax_disp/disp_data.py

return_offset_data(spins=None, spin_ids=None, field_count=None, fields=None):

Spectrometer notes

Varian / VnmrJ

In some pulse sequences, the following is seen:

'trim' is a basic timeunit and the total spinlock time is calculated as 2.0*ncyc*trim
b1 = getval("b1"),                      /* spin-lock field, Hz! */  
deltadof2 = getval("deltadof2"),        /* offset for N15 spinlock */