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Acoustic Spectroscopy,Experimental Methods and Research

Linde B.

Molecular and Quantum Acoustics

2006

Vol. 27

169-188

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.

Relaxation Phenomena In The Nematic Phase of Liquid Crystal Near Phase Transition

Balcerzak A.

Molecular and Quantum Acoustics

2005

Vol. 26

7-13

Absorption of ultrasonic longitudinal waves in the nematic liquid crystal 1-(trans- 4-hexylcyclohexyl)-4-isothiocyanatobenzene (6CHBT) was measured in the temperature (24-56oC) and frequency (3.2-100 MHz) ranges. In the region of the phase transition the anomalous absorption has been observed. This absorption rapidly increases when the frequency of the ultrasonic wave decreases. The experimental results for the nematic phase were analysed and two relaxation processes have been found. Relaxation parameters for both processes were calculated. The process with the longer relaxation time is connected with the order parameter changes. The isomeric changes in the hexyl chain of the 6CHBT molecule is the origin of the process characterized by the shorter relaxation time.