Scattering of light from entropy fluctuations in 3He–4He mixtures

1968 ◽  
Vol 46 (17) ◽  
pp. 1895-1903 ◽  
Author(s):  
B. N. Ganguly ◽  
A. Griffin
Keyword(s):  
Critical Point ◽  
Concentration Fluctuations ◽  
Complete Analysis ◽  
Second Sound ◽  
Hydrodynamic Equations ◽  
Normal Fluid ◽  
Strongly Coupled ◽  
Scattering Of Light ◽  
First Sound ◽  
Scatter Light

In 1957, Gor'kov and Pitaevskii showed that second sound in 3He–4He mixtures is strongly coupled into the concentration fluctuations, which, in turn, scatter light quite strongly (especially near the critical point). In this paper, we give a more complete analysis of the fluctuations in density, entropy, and concentration. Our discussion is based on the hydrodynamic equations of Khalatnikov, which assume that the 3He atoms move with the normal fluid, and for simplicity we omit all dissipative coefficients. If we limit ourselves to scattering from density and concentration fluctuations, our results for the first and second sound intensities agree essentially with those of Gor'kov and Pitaevskii. Near the critical point, second sound scatters light about six times more strongly than first sound does.

scholarly journals Two-fluid hydrodynamics of a Bose gas including damping from normal fluid transport coefficients

2000 ◽  
Vol 78 (5-6) ◽  
pp. 415-432 ◽  
Author(s):  
T Nikuni ◽  
A Griffin ◽  
E Zaremba
Keyword(s):  
Fluid Transport ◽  
Transport Coefficients ◽  
Thermal Fluctuations ◽  
Bose Gas ◽  
Second Sound ◽  
Hydrodynamic Modes ◽  
Normal Fluid ◽  
Strongly Coupled ◽  
Fluid Hydrodynamics ◽  
Two Fluid

We extend our recent work on the two-fluid hydrodynamics of the condensate and noncondensate in a trapped Bose gas by including the dissipation associated with viscosity and thermal conduction in the thermal cloud. For purposes of illustration, we consider the hydrodynamic modes in the case of a uniform Bose gas. A finite thermal conductivity and shear viscosity give rise to a damping of the first and second sound modes, in addition to the damping found previously due to the lack of diffusive equilibrium between the condensate and noncondensate. The relaxational mode associated with this equilibration process is strongly coupled to thermal fluctuations and reduces to the usual thermal diffusion mode above the Bose-Einstein transition. In contrast to the standard Landau two-fluid hydrodynamics, we predict a damped mode centered at zero frequency, in addition to the usual second sound doublet.PACS Nos.: 03.75.Fi, 05.30Jp, 67.40.Db

Stimulated scattering of light in gases near the critical point

1983 ◽  
Vol 13 (1) ◽  
pp. 76-77 ◽  
Author(s):  
V S Zuev ◽  
O A Logunov ◽  
Aleksandr V Startsev ◽  
Yu Yu Stoĭlov
Keyword(s):  
Critical Point ◽  
Stimulated Scattering ◽  
Scattering Of Light

Kinetics of low-threshold stimulated thermal scattering of light in gases near the critical point

1984 ◽  
Vol 14 (7) ◽  
pp. 986-988
Author(s):  
V S Zuev ◽  
O A Logunov ◽  
Aleksandr V Startsev ◽  
Yu Yu Stoĭlov
Keyword(s):  
Critical Point ◽  
Scattering Of Light ◽  
Low Threshold ◽  
Thermal Scattering ◽  
Kinetics Of

scholarly journals Super black eyespots of the Eyed elater

2019 ◽  
Author(s):  
Victoria L Wong ◽  
Paul E Marek
Keyword(s):  
Incident Light ◽  
Natural World ◽  
Surface Structures ◽  
Anatomical Structures ◽  
Scattering Of Light ◽  
Click Beetle ◽  
Absorption Of Light ◽  
Complete Absorption ◽  
Vertically Aligned ◽  
Scatter Light

Scattering of light by surface structures leading to near complete structural absorption creates an appearance of “super black.” Well known in the natural world from bird feathers and butterfly scales, super black has evolved independently from various anatomical structures. Due to an exceptional ability to harness and scatter light, these biological materials have garnered interest from optical industries. Here we describe the false eyespots of the Eyed elater click beetle, which attains near complete absorption of light by an array of vertically-aligned microtubules. These cone-shaped microtubules are modified hairs (setae) that are localized to eyespots on the dorsum of the beetle, and absorb 96.1% of incident light (at a 24.8° collection angle) in the spectrum between 300 – 700 nm.

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