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The resonance frequency shift of an acoustic rectangular chamber due to the pressure of a rigid sphere has been measured for the n = 1, 2 modes as a function of sphere size and position. The position dependence has sinusoidal and dc components. A simple excluded volume model and boundary perturbation theory were used to explain the data. The calculations can account for the sinusoidal behavior, but not for the dc shift. Also measured were the frequency shift, due to a thin disk of the same cross section and a cylinder of the same cross section and volume as the sphere, and the p2/p1 ratio at the wall as a function of sphere position. [Work supported by NASA.]

The acoustic radiation force on a rigid sphere ha• been measured in a resonance chamber for a range of pressures, positions, sizes, and for various gases. In the low to medium intensity region (< 150 dB) the measured force is consistent with King's theory [Proc. R. Soc. London, Ser. A 147, 212 (1934)] when analyzed in terms of the fundamental pressure. However, in the high intensity region (> 150 dB), the measured force starts to deviate systematically from King's calculations.

The properties of a dual-temperature resonant chamber to be used for acoustical levitation and positioning have been theoretically and experimentally studied. The predictions of a first-order dissipationless treatment of the generalized wave equation for an inhomogeneous medium are in close agreement with experimental results for the temperature dependence of the resonant mode spectrum and the acoustic pressure distribution, although the measured magnitude of the pressure variations does not correlate well with the calculated one. Ground-based levitation of low-density samples has been demonstrated at 800 °C, where steady-state forces up to 700 dyn were generated.

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The resonance frequency shift of an acoustic rectangular chamber due to the presence of a rigid sphere has been measured for l = 1,2 modes as a function of sphere size and position. The frequency shift is the results of volume exclusion and wave scattering. An analytical Green's function calculation was used to explain the data, providing excellent agreement between the measured and the calculated values. Also reported are similar measurements for a thin disk and the ratio of second harmonic to fundamental pressure as a function of sphere position. The measurement shows that the sphere reduces the first harmonic content, with sharply peaked suppression minima at specific sphere positions.

Lattice frequencies and energies are calculated with an n-6 atom-atom potential to fit recent Raman spectra of solid N2 and neutron scattering data of solid CO2. It is found that n ∞ 9 provides a slightly better fit than the previously used n = 12. The atom-atom potential, giving a fit of about 10% to experimental data, is compared with other potentials and it is pointed out that it can be modified and supplemented by other terms (a quadrupole potential) so as to yield a more realistic potential model, having the expected forms at the limits of large and small intermolecular distance.

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