Sonoluminescence, metal carbonyls

Suslick KS, Flint EB, Grinstaff MW, Kemper KA (1993) Sonoluminescence from metal carbonyls. J Phys Chem 97 3098-3099... 

A second spectroscopic thermometer comes from the relative intensities of atomic emission lines in the sonoluminescence spectra of excited-state metal atoms produced by sonolysis of volatile Fe, Cr, and Mo carbonyls. Sufficient spectral information about emissivities of many metal atom excited states are available to readily calculate emission spectra as a function of temperature. Because of this, the emission spectra of metal atoms are extensively used by astronomers to monitor the surface temperature of stars. From comparison of calculated spectra and the observed MBSL spectra from metal carbonyls, another measurement of the cavitation temperature was obtained.6 The effective emission temperature from metal atom emission during cavitation under argon at 20 kHz is 4,900 250 K. 

The effective temperature that was resolved from metal carbonyl sonoluminescence (5,150 300 K for Fe, 4,700 400 K for Cr, and 4,750 400 K for Mo) was in excellent agreement with the peak temperature obtained by sonication of silicone oil under argon. The peak temperature of the bubble could be controlled by the addition of hydrocarbon gases (C1-C3) to the solutions. As the mole fraction of the gas increased and as the polytropic ratio decreased, the anticipated temperature from adiabatic compression decreased. 

Ultrasonic irradiation of volatile organometallics (such as Fe(CO)s or Cr(CO)6) in a low volatility organic liquid produces intense sonoluminescence that corresponds to the known atomic emission lines of the metals, again analogous to flame emission. Hot-spot temperatures are sufficient not only to dissociate all the CO ligands fl om the metal complex, but also to produce excited state metal atoms. Figure 5 shows a typical MBSL spectrum from a metal carbonyl solution (Cr(CO)e in this example). Note the intense line emission from the metal atom excited states as well as bands from excited states of the diatomics, C2 and CH. This metal atom emission provides a useful spectroscopic thermometer, as described later. 

CONTENTS Introduction to Series An Editor s Foreword, Albert Padwa. Introduction, Timothy J. Mason. Historical Introduction to Sonochemistry, D. Bremner. The Nature of Sonochemical Reactions and Sonoluminescence, M.A. Mar-guli. Influence of Ultrasound on Reactions with Metals, 6. Pugin and A.T. Turner. Ultrasonically Promoted Carbonyl Addition Reactions, J.L. Luche. Effect of Ultrasonically Induced Cavitation on Corrosion, W.J. Tomlinson. The Effects ... 

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