|NUKLEONIKA 2013, 58(3):375-378
BLOCH-SIEGERT SHIFT IN THE RABI OSCILLATIONS ON THE "DRESSED" ELECTRON SPIN STATES
Ryhor Fedaruk1, Agnieszka Kolasa1, Alexander P. Saiko2
1 Institute of Physics, University of Szczecin,
15 Wielkopolska Str., 70-451 Szczecin, Poland
2 Scientific-Practical Materials Research Centre National Academy of Sciences of Belarus,
19 P. Brovki Str., 220072 Minsk, Belarus
Using electron paramagnetic resonance (EPR) at Rabi frequencies, we study the Bloch-Siegert effect in the coherent dynamics of electron spin states driven by a bichromatic radiation consisting of a transverse microwave (MW) and longitudinal radio frequency (RF) fields. The Rabi oscillations on the electron spin states “dressed” by the MW field are observed at the double resonance, when the MW frequency equals the Larmor frequency of the spin system and the frequency omegarf of the RF field is close to the Rabi frequency omega1 in the MW field. The dispersive (|omegarf – omega1| ~ omegarf, omega1) and near-resonant (omegarf ~ omega1) regimes are investigated. We demonstrate that the Bloch-Siegert shift increases with increasing RF amplitude and at the fixed RF amplitude it has the largest values in the “low-frequency” (omegarf < omega1) range of the dispersive regime. Experimental results were obtained in the time-resolved EPR for E’1 centres in quartz.