Jul 30, 2025
Version 2
Spin Echo with Half-Echo Acquisition V.2
- Alexander L. Paterson1
- 1National Magnetic Resonance Facility at Madison (NMRFAM), University of Wisconsin-Madison, Madison, WI, United States
Protocol Citation: Alexander L. Paterson 2025. Spin Echo with Half-Echo Acquisition. protocols.io https://dx.doi.org/10.17504/protocols.io.q26g71mjqgwz/v2Version created by NMRFAM Facility
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: June 25, 2025
Last Modified: July 30, 2025
Protocol Integer ID: 221026
Keywords: Materials Spin-1/2 Spin Echo, spin echo, spin echo spectrum, spin echo with half, echo acquisition purpose, echo acquisition, dimensional spin echo, proper rotor synchronization, background signals from rotor, rotor, integer quadrupole nucleus, pulse pair, spectrum, stator component, timing delay
Funders Acknowledgements:
National Science Foundation
Grant ID: 1946970
Abstract
Purpose
To acquire a spin echo spectrum of a spin-1/2 or half-integer quadrupole nucleus with half-echo acquisition.
Scope
This SOP is used to acquire a one-dimensional spin echo spectrum with half-echo acquisition, using a 90°-180° or 90°-90° pulse pair. It is effective at suppressing background signals from rotor or stator components and at mitigating long ringdown periods. When conducted under MAS it should be rotor synchronized. Proper rotor synchronization requires adjustment of the pre-acquisition delay to account for timing delays which may differ from instrument to instrument.
Guidelines
This sequence imposes a T2’ weighting factor on the intensities of the resonances; while typically negligible for short echo periods, this should be considered when using long echo periods.
When used for an integer spin nucleus, a solid echo (90°-90°) must be used instead of a Hahn echo (90°-180°).
Materials
Definitions:
- MAS: Magic angle spinning
- νrf: rf power
- T1: Longitudinal relaxation time constant
- T2’: Homogeneous transverse relaxation time constant
Appendix:
Figure 1. 13C Hahn echo with correctly set value of d7 and mis-set value of d7. While both spectra are correctly phased, the mis-set value leads to a baseline roll, complicating integrations and requiring post-processing.
Troubleshooting
Before start
User should be familiar with the power limitations and duty cycle of the probe being used.
Expected amount of time SOP will use: 30 minutes
Procedure
Load the pulse program hahnecho.nmrfam.
Set the following initial parameters:
Set the 90° pulse length, p1, and the 90° pulse power, plw1, to a previously optimized 90° pulse.
Set the length of the echo pulse by setting cnst2 to either 2 (for a 180° Hahn echo) or 1 (for a 90° solid echo).
Set the recycle delay, d1, to 1.3 × T1 if optimizing for sensitivity, or 5 × T1 if quantitative intensities are desired.
Note
Recall that the intensities are modulated by a T2’ weighting factor.
Set the spinning rate constant, cnst31, to the MAS rate in Hz.
If the sample is static, i.e., not spinning, set cnst31 to 1e6.
Set the rotor period loop counter, l1, to an initial value of 1.
If the sample is static, set l1 to the desired echo delay in microseconds.
Set the pre-acquisition delay, d7, to the initial value calculated by del7.
Note
If cnst2 is changed, d7 will need to be manually updated to account for the different echo pulse length.
If heteronuclear decoupling is desired, add the -Ddec flag to zgoptns.
Set the decoupling program, CPDPRG2, pulse length, PCPD2, and pulse power, plw12, to previously optimized values.
Set the acquisition time aq to a sufficiently long value such that the FID is not truncated.
Safety information
If high-power decoupling (>10 kHz νrf) is used, aq must be less than 50 ms.
Acquire an initial spectrum. If any background signal is sufficiently suppressed, proceed to the next step. Otherwise, increase l1 and repeat this step.
Note
As l1 is increased, the accuracy of the relative intensities will be reduced due to the T2’ weighting factor.
Observe the baseline of the spectrum. If a significant first-order phase correction (> |60°|) is required, adjust d7 until the required phase correction is minimized.
Note
del7 will typically overestimate d7 by a few microseconds. Only small adjustments (1 µs – 10 µs) should be necessary to obtain an optimal value.
Increase the number of scans, ns, to a value which will provide adequate signal-to-noise while respecting the phase cycle.
Acquire the optimized spectrum.
Protocol references
Y. Nishiyama and N. T. Duong, “Practical guides for 1H detected solid-state NMR under fast MAS for small molecules,” Journal of Magnetic Resonance Open, vol. 10-11, p. 100062, Jun. 2022.
DOI: 10.1016/j.jmro.2022.100062
Example Data at 1.1 GHz: usnan.org/ark:/83454/e1df37eab0-5944-47f4-b1c2-3b009a7af51c
Example Data at 900 MHz: usnan.org/ark:/83454/e11ee9e85a-9dc6-46e2-b66d-e47121bc7bae
Example Data at 600 MHz: usnan.org/ark:/83454/e12383feba-4776-4118-a367-a2ee5adc2f69