Ultrasonic Absorption and Pretransitional Phenomena Near a Second Order Nematic-Smectic a Phase Transition

Ultrasonic attenuation in CBOOA near the nematic-smectic-a transition

“…Although a theoretical model has been available for some time [26], experimental study of the ultrasonic absorption has been hampered mainly by the difficulty of making measurements in oriented samples over a wide frequency range. Using this technique we established recently the existence of a pretransitional relaxation in the MHz range [27] and to explain our results F. Brochard has shown that the overdamping of the second sound is the origin of this low frequency relaxation [28].…”

“…Furthermore, it requires only small liquid samples of about 5 ml. We have already used such a device in earlier studies [27,36]. For the present study many improvements have been made which reduce the scatter of the very-lowfrequency measurements.…”

Relative behaviour of sound absorption and dispersion near the nematic-smectic-A phase transition in TBBA and CBOOA : comment and new results

“…The study that Kiry and I made of the A-N transition in CBOOA [6][7][8] revealed that this transition is characterized by weak pretransitional effects. Our analysis above TAN [8] showed that the ultrasonic absorption has two components.…”

“…At the smectic-A-nematic (A-N) phase transition, however, ultrasonic measurements are rather scarce [3][4][5][6][7][8][9] and the current situation appears confusing. This letter is an attempt to clarify this situation.…”