No abstract available

[en] For the first time experimental observations are made of the oscillation in the intensity of the unshifted line and in the intensities of the US satellites when the γ-resonance radiation is modulated by the coherent US excitation. It is stated that the coherent US can be excited in the investigated sample if the US amplitude is transmitted homogeneously from the generator to the sample. A special sample-unit is described which provides a homogeneous transmission, and it is shown that the lifetime of the US phonons is not substantial and does not affect the oscillation of the absorption line intensities. (author)

[en] A theoretical analysis is made on nuclear transition probability from the ground state to the sublevels of the first excited state under the influence of γ-quanta and external acoustic excitation. When the electric field possesses an axial symmetry, Hsub(eff)=0 and the ultrasonic oscillation frequency Ω satisfies the resonance condition between the nuclear sublevels, there are two possible cases of transition if the energy of the monochromatic γ-quanta satisfies the resonance. The two cases are analyzed depending on the ultrasonic oscillation power and the angle between γ-bunch and the direction of ultrasonic excitation. It is shown that for A₀/lambda<<1 and phi=π/2 the 1→2→3 transition is more plausible. When A₀/lambda>approximately 1, theta=0, phi=0, the 1→3 transition is more probable. (author)