The electrocapillary mechanism driving the oscillatory hydrodynamic modes of a "clean" (i.e., without organic contaminants) mercury drop in the absence of oxygen and in neutral and basic solutions was investigated. The electrocapillary driver can be mimicked by imposition of an external field oscillating with frequency vmax and amplitude AK about an appropriate voltage K0, where K0 is referenced to a standard potential. The hydrodynamic mode selection for a given K0 is controlled in a strictly reproducible and reversible manner by adjustment of the driver frequency KIMX and the voltage AK.
Vibrational relaxation in water vapor has been observed using both ultrasonic velocity dispersion and absorption. The raw data were corrected for real-gas effects and for classical absorption. Results are compared with those of other investigators. Observed relaxation times appear much too short to be explained by a simple V-T process, and are interpreted in terms of a V-R transfer mechanism. Values of kVR range from about 1×108 sec−1 atm−1 at 374 K to 6×108 sec−1 atm−1 at 946 K.
A computer-controlled ultrasonic interferometer has been utilized for exploring room-temperature relaxation of gaseous SiF4–Ar and SiF4–Ne mixtures. A single relaxation process was observed for all mixtures, and the relaxation rates, 1/pτ, were found to vary linearly with the mole fraction of added argon or neon. Analysis of the mixture relaxation data shows that collisions between SiF4 molecules and either Ar or Ne atoms are less efficient for V−T transfer than are SiF4 self-collisions. This result can be explained within the Schwartz–Slawsky–Herzfeld formulation if it is assumed that a steep repulsive potential (i.e., the 7:28 function) is operative for SiF4–SiF4 collisions, while the repulsive interaction for SiF4–noble gas collisions is treated as being between a molecule obeying a 7:28 law and an atom characterized by a 6:12 function.
A study was made at various sea-state conditions of the coherence of an acoustic signal that has undergone one surface reflection. The source and receivers were bottom-mounted in deep water near Bermuda. Two types of correlation measurements were made: (1) crosscorrelation of a surface-reflected signal received at two hydrophones 500 ft apart, and (2) crosscorrelation of a surface-reflected signal with a replica of the transmitted signal. The signal consisted of random noise for (1) and pseudorandom noise for (2). In both cases, the signal was limited to a 300-cps band centered at 750 cps. Results indicate that the coherence decreases with increasing sea state in a linear manner. Normalized crosscorrelation coefficients obtained from the two hydrophones decrease from about 0.9 for a waveheight of 5 ft to 0.5 for a waveheight of 20 ft. Values obtained for the single-hydrophone output and replica fall off at a much slower rate. [Work supported by the Bureau of Ships, U. S. Navy.]
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