Effective field integral subtraction by the combination of spin echo and resonance spin echo

Physical Chemistry Chemical Physics

Volumn 7, Issue 6, 2005, Pages 1245-1249

  Häussler, Wolfgang ^a,c   Schmidt, Ulrich ^b  

^a INSTITUT LAUE LANGEVIN   (France)

^b UNIVERSITY OF HEIDELBERG   (Germany)

^c TECHNICAL UNIVERSITY OF MUNICH   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

CONFERENCE PAPER; ELECTRICITY; ENERGY TRANSFER; FOURIER TRANSFORMATION; MAGNETIC FIELD; MATHEMATICAL MODEL; NEUTRON SCATTERING; POLARIZATION;

EID: 16344368828     PISSN: 14639076     EISSN: None     Source Type: Journal    
DOI: 10.1039/b419281h     Document Type: Conference Paper

References (13)

1. F. Mezei, Z. Phys., 1972, 255, 146.
2. F. Mezei, in Neutron Spin Echo, Lecture Notes in Physics, ed. F. Mezei, Springer, Berlin, Heidelberg, New York, 1980, vol. 128.
3. (a) R. Gähler and R. Golub, Z. Phys. B, 1987, 65, 269;
4. (b) R. Golub and R. Gähler, Phys. Lett. A, 1987, 123, 43.
5. D. Dubbers, P. El-Muzeini, M. Kessler and J. Last, Nucl. Instrum. Methods Phys. Res., Sect. A, 1989, 275, 294.
6. F. Bloch and A. Siegert, Phys. Rev., 1940, 57, 522.
7. W. Häussler, U. Schmidt, G. Ehlers and F. Mezei, Chem. Phys., 2003, 292, 501.
8. W. Häussler and U. Schmidt, in preparation.
9. The π flip results in a reflection of the spin by the RF field. From geometry, the angle after the reflection is known [eqn. (7)] (for a more detailed explanation see for example: W. Häussler, Dissertation, University of Heidelberg, 1998).
10. U. Schmidt, S. Biche, W. Häußler and D. Dubbers, Physica B, 1997, 234-236, 1133.
11. T. Keller, R. Golub, F. Mezei and R. Gähler, Physica B, 1998, 241-243, 101.
12. M. Köppe, Dissertation, TU München, 1998.
13. The appearance of two echo groups is a consequence of the combination of NSE and NRSE coils tuned to π-half flippers. At the beginning of the NSE arm, the spin is flipped in a standard static flipper by π/2. The spin phase accumulated in the subsequent NSE coil varies with the neutron wavelength. After the second static π-half flipper, the spins are distributed in a plane defined by the flip coil's field direction. At the beginning of the NRSE setup, the first resonant flip takes place. This flip is a π-half flip only for these spins which are directed perpendicularly to the RF field. The RF field rotates (rotating wave approximation). Thus, only these spins, which are directed perpendicularly to the RF field (and parallel to the NSE field), undergo a 'correct' π-half flip, classically spoken. On the one hand, the final polarization is limited to 50%. On the other hand, the polarization does not depend on the field direction of the NSE precession region for symmetry reasons. Therefore, two echo groups appear by tuning the NSE field integral. A more detailed explanation will be given elsewhere (see ref. 7).