Measurement of spin-spin relaxation time T2 at very low magnetic field
by means of the Fast Field Cycling NMR method

POSTER by aFerrante G., Canina D., aBonardi E., aPolello M., aSykora S., bGolzi P., bVacchi C., cStevens R.
aStelar srl, Mede (PV), Italy     bUniversity of Pavia, Department of Electronics, Pavia, Italy     bMolecular Specialties Inc, Milwaukee, Wi

presented at the

48th ENC Conference, Daytona Beach, FL (USA), April 22-27, 2007, and at the
5th Conference on Field Cycling NMR Relaxometry, Torino, Italy, May 31 - June 2, 2007.

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Field Cycling NMR is a well-established and reliable method for measuring the spin-lattice relaxation time T1 and its dependence on the magnetic field strength. This is also the only NMR method capable to extend these measurements down to very low field. Unfortunately, because of instrumental limitation, it was impossible till now to apply the same method for the measurement of the spin-spin relaxation time T2. This poster presents new instrumental techniques and NMR methods developed exactly to overcome that limit. The new approach makes possible the measurement of complete profiles of T2 starting from very low field (2-10 KHz) by means of Spin-Echo FC experiments.

Several T2 profiles acquired from 0.01 to 10 MHz are presented and discussed.

Notes added on May 17 and June 23, 2007:
- Due to considerable contribution of diffusion effects, it would have been more proper to call the acquired data spin-echo profiles rather than T2 profiles. The principle point of this poster is to show that spin-echo FFC data can now be acquired at all - a fact which implies a considerable progress in the quality of FFC-NMR instrumentation. The detailed interpretation of the data is a different matter.
- The present affiliation of S.Sykora is with Extra Byte, while the reported affiliation refers to the time when the first spin-echo FFC echo-decay was successfully acquired. Stan Sykora has measured the very first true fast-field-cycling spin-echo multi-block decay at Stelar premises on November 22, 2007 (see the measurement protocol) using the same sequence as the one described in this poster. At that time, however, it was impossible to accumulate the signal since the field instability precluded accumulation of phase-detected data and the accumulation of modulus was not yet implemented.

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