The phonon spectrum injected by a metallic point contact : an FLN study

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Abstract
A metallic point contact, consisting of a tungsten whisker pressed onto a tungsten film, is used to inject high-frequency phonons into a ruby crystal kept at 1.5 K. The effective phonon temperature near the point contact is measured via the temperature dependences of the position and width of the R1 line of the Cr3+. High Spectral resolution is provided by the technique of fluorescence line narrowing. The temperatures observed range up to 300 K, demonstrating the effectiveness of the point contact as a generator of high-frequency phonons.