Quantum coherence phenomena in x-ray optics

The effects of quantum coherence in X-ray optics at nuclear transitions are investigated from a theoretical point of view. First, we introduce the general concept of the decaying dressed states and present a classification of the quantum coherence effects in a three-level coherently driven system. Second, we show that the interference effects may appear in X-ray radiation at the nuclear transitions under the condition of the nuclear level anti-crossing. This effects are similar to electromagnetically induced transparency, which has been widely studied earlier at the electronic transitions in optics. We also suggest a new technique for inhomogeneous line narrowing at nuclear transitions. This technique is based on the combined action of RF and DC fields and adopted to be applied in the M?ossbauer spectroscopy. Numerical simulation of a simple model with the dipole-dipole interaction is presented in order to demonstrate the efficiency of the technique. Finally, we study the possibility to suppress the nuclear elastic forward scattering in the synchrotron experiments using trains of pulses. A numerical model is developed to confirm this possibility and the main issue of relative phases of consecutive pulses is discussed.