title: Low-field NMR measurement procedure when SQUID detection is used.
abstract: In reported low-field nuclear magnetic resonance (NMR) measurements using Superconducting Quantum Interference Device (SQUID) detection, the pre-polarizing magnetic field has been usually oriented orthogonal to the measuring field, B(p) perpendicular B(m). Melton et al. systematically analyzed the consequences of B(p) decay in time after turnoff and showed that this decay should be nonadiabatic. We evaluated our measuring procedure in the light of that analysis, and found good quantitative agreement. It was showed that, when the decay time constant is comparable to the precession period of the magnetization of the sample, M, the optimum procedure is to orient B(p) parallel to B(m) and to apply a pi/2 pulse to flip M, similar as in the case of conventional NMR.
authors.affiliation: Institute of Bio- and Nanosystems, Research Center Juelich, D-52425 Juelich, Germany. l.qiu@fz-juelich.de
authors.forename: Longqing
authors.initials: L
authors.lastname: Qiu
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Krause
authors.forename: Alex I
authors.initials: AI
authors.lastname: Braginski
authors.forename: Andreas
authors.initials: A
authors.lastname: Offenhäusser
mesh_terms: D004867:Equipment Design / Q000295:instrumentation / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods*; D008280:Magnetics; D008962:Models, Theoretical; D011789:Quantum Theory; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity