Double quantum transition as the origin of the central dip in the z-spectrum of HDO in variably stretched gel.
The 2H NMR spectrum of HDO in gelatin gel, that is stretched inside silicone rubber tubing, displays a well resolved doublet. Spectra were obtained with a range of offset frequencies of partially saturating radio-frequency (RF) radiation. The resulting steady-state irradiation envelope (also referred to as a 'z-spectrum') has the peculiar feature that maximal suppression of the doublet occurs when the irradiation is applied exactly at the centre frequency, between the two HDO peaks. We present a quantum mechanical explanation for this phenomenon. It is shown that the phenomenon is the result of double quantum transitions. The analysis is extendable to more complex quadrupolar and dipolar-coupled systems of other nuclides. It has implications for enhancement of contrast in magnetic resonance imaging of heterogeneous systems using dipolar and quadrupolar interactions.
Eliav
Uzi
U
School of Chemistry, Tel-Aviv University, Ramat Aviv 69987, Israel.
Naumann
Christoph
C
Navon
Gil
G
Kuchel
Philip W
PW
D000465:Algorithms; D016880:Anisotropy; D005780:Gelatin / Q000737:chemistry* / Q000528:radiation effects; D005782:Gels / Q000737:chemistry* / Q000528:radiation effects; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011789:Quantum Theory
D005782:Gels; D005780:Gelatin