Naslov
Nuclear Magnetic Spin-Noise: Non-linearity, Frequency Shifts, and the Spin Noise Tuning Optimum (SNTO)

Autori
Nausner, Martin ; Schlagnitweit, Judith ; Smrečki, Vilko ; Yang, Xu ; Jerschow, Alexej ; Müller, Norbert

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
50th ENC Long Abstracts / Frydman, Lucio - Santa Fe (NM) : ENC Conference, 2009, 108-108

Skup
50th ENC, Experimental Nuclear Magnetic Resonance Conference, Asilomar, 2009

Mjesto i datum
Pacific Grove (CA), Sjedinjene Američke Države, 29.03.2009. - 03.04.2009

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
NMR spectroscopy; spin noise spectra

Sažetak
Nuclear magnetic spin noise appears in the absence of any external radiofrequency driving field, when the spins’ magentic moments are tightly coupled to the pickup coil [1]. The line shapes of the observed proton nuclear spin noise spectra depends in complex ways on the properties of the resonance circuit, the number of spins present, transverse relaxation, inhomogeneous broadening, radiation damping and temperature. Although this is a power spectrum it exhibits dispersion-like line shape, especially in the CH3-region. According to theory [2] if the tuning frequency of the circuit omega(c) is equal or close to the Larmor frequency the spin noise signal possesses a negative deviation from the otherwise flat baseline. We find the symmetrical „ dip“ line shape at a considerable offset, which we call „ spin noise tuning optimum (SNTO)“ , from the normal tuning optimum where this dispersion like line shape was observed. The peak areas do not reflect the number of nuclei, for instance the OH proton signal is much larger than the signal of the CH3 groups. While the base line in a spin noise power spectrum has a positive offset corresponding to the thermal noise background of the entire electronics, a negative peak or „ dip“ represents a situation of „ less than thermal noise“ and a positive peak or „ bump“ means „ more than thermal noise“ . This behaviour inevitably causes non-linearity of the spin noise power, which can be traced to the influence of the total z-magnetization M(z) in simulations. The 13C satellites of the CH3 groups are clearly visible presenting amplitudes far higher than one would expect for this natural isotope abundance sample. References [1] Sleator T., et al., Phys. Rev. Lett. 55, 1742, 1985. [2] McCoy M.A., Ernst R.R., Chem. Phys. Lett. 139, 587, 1989.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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