Ultrasonic properties of a suspension of microspheres supporting negative group velocities
The ultrasonic attenuation coefficient, phase velocity, and group velocity spectra are reported for a suspension that supports negative group velocities. The suspension consists of plastic microspheres with an average radius of 80 microm in an aqueous medium at a volume fraction of 3%. The spectra a...
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Veröffentlicht in: | Physical review letters 2007-09, Vol.99 (12), p.124301-124301, Article 124301 |
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Hauptverfasser: | , |
Format: | Artikel |
Sprache: | eng |
Online-Zugang: | Volltext |
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Zusammenfassung: | The ultrasonic attenuation coefficient, phase velocity, and group velocity spectra are reported for a suspension that supports negative group velocities. The suspension consists of plastic microspheres with an average radius of 80 microm in an aqueous medium at a volume fraction of 3%. The spectra are measured using a broadband method covering a range from 2 to 20 MHz. The suspension exhibits negative group delays over a band near 4.5 MHz, with the group velocity magnitude exceeding 4.3 x 10(8) m/s at one point. The causal consistency of these results is confirmed using Kramers-Kronig relations. |
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ISSN: | 0031-9007 1079-7114 |
DOI: | 10.1103/PhysRevLett.99.124301 |