C. Vanderstruijf et al., INFLUENCE OF HIGH ORIENTATIONAL ORDER ON THE SHAPE OF THE ECHO RESPONSE FROM A HAHN PULSE SEQUENCE, Journal of magnetic resonance [1997], 130(2), 1998, pp. 253-261
Citations number
20
Categorie Soggetti
Physics, Atomic, Molecular & Chemical","Biochemical Research Methods
The amplitude modulations in the simulations of the Hahn echo response
s from cholestane spin labels in samples characterized by a high degre
e of orientational order are shown to arise from the use of ''soft'' p
ulses, Soft pulses have a limited spectral range and cover only a smal
l portion of the CW-ESR spectra, so that not all the spins are on-reso
nance. The magnetization vectors of the off-resonance spins only parti
ally tilted away from the laboratory z axis, the direction of the appl
ied static magnetic field. They thus contribute oscillating components
to the magnetization in the xy plane. The contribution from the off-r
esonance spins to the Hahn echo formation is significant in highly ori
ented samples, but cancels out in samples exhibiting a small degree of
order. Experimental echo responses obtained from CSL molecules embedd
ed in rigid matrices of eggPC bilayers and the liquid crystalline mate
rials ZLI and MBBA confirm the theoretical predictions. (C) 1998 Acade
mic Press.