Quasar computing module (introduced in dmfit 2005
version)
JeanPaul Amoureux; UCCS,
CNRS8181, 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 :
JeanPaul Amoureux; UCCS, CNRS8181, Lille, France
Quasar determines the signal
that can be observed with powder samples, after a perfect
p/2
pulse with very large RFamplitude (much larger than all microscopic
interactions).

The sample can be static, or in rotation about one axis (VAS,
or MAS).

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
nonsecular terms.^{1}

Possible interactions are : CSA (1^{st}order), quadrupole interaction (2^{nd}order); heteronuclear scalar and
dipolar interactions to the 1^{st}order.

2^{nd}order crossterms (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, 89478960, 1992.
2  M. Mehring, SpringerVerlag 1983.