Physics:Landau–Placzek ratio
Landau–Placzek ratio is a ratio of the integrated intensity of Rayleigh scattering to the combined integrated intensity of Brillouin scattering of a triplet frequency spectrum of light scattered by homogenous liquids or gases. The triplet consists of two frequency shifted Brillouin scattering and a central unshifted Rayleigh scattering line split. The triplet structure was explained by Lev Landau and George Placzek in 1934 in a short publication,[1][2] summarizing major results of their analysis. Landau and Placzek noted in their short paper that a more detailed discussion will be published later although that paper does not seem to have been published. However, a detailed discussion is provided in Lev Landau and Evgeny Lifshitz's book.[3] The Landau–Placzek ratio is defined as
- [math]\displaystyle{ R_{LP} = \frac {I_c} {2I_B} }[/math]
where
- [math]\displaystyle{ I_c }[/math] is the integral intensity of central Rayleigh peak
- [math]\displaystyle{ I_B }[/math] is the integral intensity of Brillouin peak.
The Landau–Placzek formula provides an approximate theoretical prediction for the Landau–Placzek ratio,[4][5]
- [math]\displaystyle{ R_{LP} = \frac{c_p-c_v}{c_v} }[/math]
where
- [math]\displaystyle{ c_p }[/math] is the specific heat at constant pressure
- [math]\displaystyle{ c_v }[/math] is the specific heat at constant volume.
References
- ↑ Landau, L. D., & Placzek, G. (1934). Struktur der unverschobenen Streulinie. Z. Phys. Sowjetunion, 5, 172-173.
- ↑ Landau, L., & Placzek, G. (1934). Structure of the undisplaced scattering line. Phys. Z. Sowiet. Un, 5, 172.
- ↑ Landau, L. D., Pitaevskii, L. P., Lifshitz, E. M., Electrodynamics of continuous media (Vol. 8). elsevier. Section 120, pp. 428-433.
- ↑ Cummins, H. Z., & Gammon, R. W. (1966). Rayleigh and Brillouin scattering in liquids: the Landau—Placzek ratio. The Journal of Chemical Physics, 44(7), 2785-2796.
- ↑ Wait, P. C., & Newson, T. P. (1996). Landau Placzek ratio applied to distributed fibre sensing. Optics Communications, 122(4-6), 141-146.
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