Summary
The spectrum and the amplitude fluctuations of laser light propagating through liquid helium have been measured. The experimental results show that the spatial correlation function of the refractive index fluctuations present in the liquid is adequately approximated by a Gaussian. Both the light scattered by liquid helium under a 90° angle and the amplitude fluctuations of light propagating through the liquid have been measured at the λ-point. No excess scattering at 90° and no anomalous amplitude fluctuations have been observed, in agreement with the information obtained in a previous experiment by Lawson and Meyer (1).
Riassunto
Sono stati misurati lo spettro e le fluttuazioni di ampiezza di luce laser propagantesi attraverso elio liquido. I risultati sperimentali indicano che la funzione di correlazione spaziale delle fluttuazioni dell’indice di rifrazione del liquido può essere adeguatamente approssimata da una gaussiana. Al punto λ sono state misurate sia le fluttuazioni di ampiezza della luce propagantesi attraverso il liquido sia la luce diffusa a 90°. Non sono state osservate fluttuazioni anomale o diffusione anomala, in accordo con i risultati ottenuti in una precedente esperienza di Lawson e Meyer (1).
Реэюме
Были иэмерены спектр и флуктуации амплитуды распространения света лаэера череэ жидкий гелий. Экспериментальные реэультаты покаэывают, что пространственная корреляционная функция для флуктуаций козффициента преломления, присутствуюших в жидкости, адекватно апроксимируется функцией Гаусса. В λ-точке были иэмерены и свет, рассеянный жидким гелием под углом 90°, и флуктуации ампитуды распространения света череэ жидкость. Не наблюдалось аномалий в рассеянии на 90° и аномальных флуктуаций амплитуды, в соответствии с реэультатами, полученными в предыдушем зксперименте Лоусона и Мейера.
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References
A. W. Lawson andL. Meyer:Phys. Rev.,93, 259 (1954).
For examples, see:V. I. Tatarski:Wave Propagation in a Turbulent Medium (New York, 1961).
V. I. Tatarski:Wave Propagation in a Turbulent Medium, Chap. 12 (New York, 1961).
V. I. Tatarski:Wave Propagation in a Turbulent Medium, Chap. 7 (New York, 1961).
The validity of this theoretical prediction, in the case when √λL≫l, has been confirmed by an experiment on microwave scattering from nonequilibrium liquids:M. Iannuzzi:Appl. Phys. Lett.,11, 377 December 1967.
For a discussion on this subject, for instance:D. ter Haar:Elements of Statistical Mechanics, Chap. 9 (New York, 1960). See also articles quoted in ref. (1).
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Iannuzzi, M. Observation of the spectrum and the amplitude fluctuations of light propagating through nonequilibrium liquid helium. Nuovo Cimento B (1965-1970) 55, 413–418 (1968). https://doi.org/10.1007/BF02711651
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DOI: https://doi.org/10.1007/BF02711651