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RESEARCH PRODUCT

Influence of the time-coherence of light on the absorption lineshapes of low-pressure gases

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Abstract A property of ultrashort laser pulses, their redshift by interaction with matter, is extended to ordinary time-incoherent light by a change of the scale of time. It appears that the matter must be a gas at a pressure uncommonly low in the labs, and that the gas must have a hyperfine structure. The relative frequency shift is constant as a Doppler shift; the images are not blurred because the interaction is space-coherent. In the presence of a redshift, the absorption lines cannot be seen because they are as wide as the shift. This interaction may produce a part of the cosmological redshift, the energy lost at high frequencies being transferred to the 2.7 K radiation. The interaction of the light with a plasma of light atoms in a variable magnetic field produces a strange lineshape: an absorption line is split into sharp pseudo-lines; this is similar to the Ly α lines observed with various shifts in the spectrum of quasars.