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Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.

Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.

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Figure 1 Transient absorption data for 50-nm-diameter Au particles collectedwith 510-nm and 550-nm probe laser wavelengths. The insert shows the ultraviolet–visible absorption spectra of the particles.predict that the frequency should be inversely proportional to the radius R[34,35]:mðcm 1 Þ ¼ gc 1ð1Þ2pcRwhere c l is the longitudinal speed of sound in Au, c is the speed of light, and gis an eigenvalue that depends on the transverse and longitudinal speeds ofsound. For the symmetric breathing mode, D is the smallest root of D cot D = 1D 2 /4y 2 , where y = c t /c l , where c t is the tranverse speed of sound. The excellentagreement between the calculated and experimental results confirmsthat the modulations are due to the symmetric breathing mode [13].The modulations are damped because the samples are polydisperse:Different-sized particles have different vibrational periods [13]. Assuming<strong>Copyright</strong> <strong>2004</strong> <strong>by</strong> <strong>Marcel</strong> <strong>Dekker</strong>, <strong>Inc</strong>. <strong>All</strong> <strong>Rights</strong> <strong>Reserved</strong>.

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