Light diffraction in acoustic fields created by wedge-shaped and parabolic piezoelectric transducers is theoretically investigated. It is shown that the acoustic fields have a complicated amplitude-phase structure changing with the acoustic frequency. Principal characteristics of acousto-optic interaction are examined. It is demonstrated that the diffraction efficiency in the Bragg regime can approach 100% in spite of a noticeable phase mismatch.
There was presented in the paper the theoretical discussion about the ultrasonic relaxation process related to energy transfer between translational and vibrational degrees of freedom as well as with the existing of chemical isomerism. The part of the paper describes several ultrasonic equipments for measurements of absorption and velocity in very wide frequency range from hundreds kHz to tens GHz. At the end there were shown several experimental examples of possible taking the advantage of the ultrasonic spectroscopy.
4
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
In the paper there is presented the theory of vibrational relaxation in fluids as well as the experimental investigations in the Kneser liquids: tiazole and furane. From these results it was possible to conclude that in this relaxation process with one relaxation time take part all vibrational degrees of freedom.
In the present paper, the authors discuss studies carried out for many years by numerous acoustics researchers, dealing particularly with two compounds: benzene and carbon disulphide. They are typical liquids in which acoustic Kneser-type relaxation occurs, caused by an irreversible vibrational-translational (VT) transition. Since magnitudes describing the relaxation process were diverse in many papers, we have undertaken an attempt to clarify these differences and to indicate how to avoid errors resulting from instrumental imperfections and the disregard of considerable measurement errors when investigating velocity dispersion in the hypersonic range.
The velocity of ultrasound and the density were measured in the mixture of 1,3-dioxane and water in the temperature range 288-308 K. Based on the results obtained. adiabatic compressibilities were calculated from Laplace's equation. The dependence of the compressibility upon concentration indicates the formation of a stable liquid structure which we tried to compare with the solid clathrate II.