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Cryogenic Q-band (35 GHz) probehead featuring large excitation microwave fields for pulse and continuous wave electron paramagnetic resonance spectroscopy: Performance and applications
Ist Teil von
Journal of magnetic resonance (1997), 2008-02, Vol.190 (2), p.280-291
Ort / Verlag
United States: Elsevier Inc
Erscheinungsjahr
2008
Link zum Volltext
Quelle
MEDLINE
Beschreibungen/Notizen
The construction and performance of a Q-band (35
GHz) cryogenic probehead for pulse electron paramagnetic resonance and continuous wave electron paramagnetic resonance measurements with down-scaled loop gap resonators (LGRs) is presented. The advantage of the LGR in comparison to TE
012 resonators lies in the large
B
1 microwave (mw) fields that can be generated with moderate input mw power. We demonstrated with several examples that this allows optimal performance for double-quantum electron coherence, HYSCORE, and hyperfine decoupling experiments employing matched and high turning angle mw pulses with high
B
1-fields. It is also demonstrated that with very low excitation power (i.e. 10–40
mW),
B
1-fields in LGRs are still sufficient to allow short mw pulses and thus experiments such as HYSCORE with high-spin systems to be performed with good sensitivity. A sensitivity factor
Λ
rs of LGRs with different diameters and lengths is introduced in order to compare the sensitivity of different resonant structures. The electromagnetic field distribution, the
B
1-field homogeneity, the
E
1-field strength, and the microwave coupling between wave guide and LGRs are investigated by electromagnetic field calculations. The advantage and application range using LGRs for small sample diameters is discussed.