Non-coincidental Quad and CSA, 17O (I=5/2)

17O (I=5/2) quadrupolar static spectrum simulation.

The following example illustrates the simulation of NMR spectra arising from non-coincidental quadrupolar and shielding tensors. The tensor parameter values for the simulation are obtained from Yamada et. al. 1, for the \(^{17}\text{O}\) site in benzanilide.

Warning

The Euler angles representation using by Yamada et. al is different from the representation used in mrsimulator. The resulting simulation might not resemble the published spectrum.

import matplotlib as mpl
import matplotlib.pyplot as plt
from mrsimulator import Simulator, SpinSystem, Site
from mrsimulator.methods import BlochDecayCentralTransitionSpectrum
import numpy as np

# global plot configuration
mpl.rcParams["figure.figsize"] = [4.5, 3.0]

Step 1: Create the spin system.

site = Site(
    isotope="17O",
    isotropic_chemical_shift=320,  # in ppm
    shielding_symmetric={"zeta": 376.667, "eta": 0.345},
    quadrupolar={
        "Cq": 8.97e6,  # in Hz
        "eta": 0.15,
        "alpha": 5 * np.pi / 180,
        "beta": np.pi / 2,
        "gamma": 70 * np.pi / 180,
    },
)
spin_system = SpinSystem(sites=[site])

Step 2: Create a central transition selective Bloch decay spectrum method.

method = BlochDecayCentralTransitionSpectrum(
    channels=["17O"],
    magnetic_flux_density=11.74,  # in T
    rotor_frequency=0,  # in Hz
    spectral_dimensions=[
        {
            "count": 1024,
            "spectral_width": 1e5,  # in Hz
            "reference_offset": 22500,  # in Hz
            "label": r"$^{17}$O resonances",
        }
    ],
)

Step 3: Create the Simulator object and add method and spin system objects.

sim = Simulator()
sim.spin_systems = [spin_system]  # add the spin system
sim.methods = [method]  # add the method

# Since the spin system have non-zero Euler angles, set the integration_volume to
# hemisphere.
sim.config.integration_volume = "hemisphere"

Step 4: Simulate the spectrum.

sim.run()

# The plot of the simulation before signal processing.
ax = plt.subplot(projection="csdm")
ax.plot(sim.methods[0].simulation.real, color="black", linewidth=1)
ax.invert_xaxis()
plt.tight_layout()
plt.show()

1

Yamada, K., Dong, S., Wu, G., Solid-State 17O NMR Investigation of the Carbonyl Oxygen Electric-Field-Gradient Tensor and Chemical Shielding Tensor in Amides, J. Am. Chem. Soc. 2000, 122, 11602-11609. DOI: 10.1021/ja0008315