We have detected, by using stimulated emission, an atomic parity violation (APV) in the form of a chiral optical gain of a cesium vapor on the 7S-6P(3/2) transition, consecutive to linearly polarized 6S-7S excitation. We demonstrate the validity of this detection method of APV, by presenting a 9% accurate measurement of expected sign and magnitude. We stress several advantages of this new approach which fully exploits the cylindrical symmetry of the setup. Future measurements at the percent level will provide an important cross-check of an existing more precise result obtained by a different method.

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Using an optical interferomertric method, the homogeneous cavitation density of superfluid helium at T = 0.96 K is measured and found to be ρcav = 0.1338 ± 0.0002 g.cm −3 . A well established equation of state for liquid helium at negative pressures converts this to the cavitation pressure Pcav = −5.1 ± 0.1 bar. This cavitation pressure is consistent with a model taking into account the presence of quantized vortices, but disagrees with previously published experimental values of Pcav.