Quasar computing module (introduced in dmfit 2005
version)
Jean-Paul Amoureux; UCCS,
CNRS-8181, Lille, France
The QUASAR module, computing on/off angle spectra in static or MAS with multiple
interactions has been written by
Jean Paul Amoureux
please ackownledge him as :
Jean-Paul Amoureux; UCCS, CNRS-8181, Lille, France
Quasar determines the signal
that can be observed with powder samples, after a perfect
p/2
pulse with very large RF-amplitude (much larger than all microscopic
interactions).
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The sample can be static, or in rotation about one axis (VAS,
or MAS).
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Only one RF irradiation is performed: the other nuclei are
indeed not manipulated.
-
Microscopic molecular reorientations are assumed to be
negligible.
-
Hamiltonians are calculated using the AHT theory, without any
non-secular terms.1
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Possible interactions are : CSA (1st-order), quadrupole interaction (2nd-order); hetero-nuclear scalar and
dipolar interactions to the 1st-order.
-
2nd-order cross-terms (quadrupole with CSA or dipolar) are not introduced.
All interactions are described with respect to the CSA (spin
= ½), or the quadrupole (spin > ½) tensor. The relative orientations of the
different interactions with respect to the CSA (or quadrupole) tensor are
described with 3 Euler angles, according to the definition of M. Mehring.2 and in agreement with definitions used by SIMPSON.
In the case of the uniaxial dipolar interaction, only 2 polar angles are needed.
The description of isotropic scalar couplings, only requires their J values.
1 - M. Goldman, PJ. Grandinetti, A. Llor, Z. Olejniczak, JR. Sachleben, JW. Zwanziger, J.
Chem. Phys. 97, 8947-8960, 1992.
2 - M. Mehring, Springer-Verlag 1983.