Figure 1
(a) Top view of Rayleigh scattering experimental setup. Linear polarized laser beam is loosely focused on a gas target. The scattered light is recorded via an optical fiber (Φ = 600 µm) located close to the target (2 cm), which is connected to a photomultiplier tube to increase its signal gain. (b) An extension is mounted on top of the gas valve to avoid the tightly focused beam to be partially blocked by a massive valve body close to gas outlet. (c) A conical throat at the extension tip shapes the gas jet profile of preferred geometry. (d) and (e) show the angular distribution of the scattered light signal along the scattered angle θ collected with an optical fiber. d) In case of the incident beam polarized 45 degree (along \(\widehat{y}+\widehat{z}\)), a cosine square relation is observed (red-measurement, blue-calculation). (f) The angular distribution for \(\widehat{z}\)-polarized laser beam is uniform in space as the measurement also shows. The decreasing intensity for increasing height from nozzle (from 2 to 3 mm) indicates that the number of scattering particles falls with height.
