The difficult discrimination of Impulse Stimulated Raman Scattering redshift against Doppler redshift

Abstract

The Impulsive Stimulated Raman Scattering (ISRS) is a parametric light-matter interaction which shifts the frequencies of two ultrashort laser light pulses by a non-quantified transfer of energy. As ISRS has no threshold, the laser pulses may be replaced by the pulses which constitute the ordinary incoherent light. This replacement has the expected qualitative effect on the time constants required to observe ISRS: nanosecond collisional time and Raman period. It has also a qualitative effect, the frequency shifts become independent on the intensity; thus we use a new name for this avatar of ISRS: "Incoherent Light Coherent Raman Scattering" (ILCRS). The coherence makes ILCRS very different from the ordinary Raman effect proposed as an alternative to Doppler effect in the past: ILCRS is a stronger light-matter interaction, it does not blur the images, nether the spectra; the beams which receive energy are in the thermal radiation. The shifts of the spectra produced either by a Doppler effect, or by ILCRS are very similar. However ILCRS is subject to a dispersion which perturbs slightly the spectra. ILCRS is the key of a model of quasars which explains all observations, without any new matter or physical theory: no fast moving cloud, no dark matter, no variation of the fine structure constant, no invisible object. The redshifts and the thermal radiation produced by ILCRS should not be neglected a priori.