ANALYTICAL CALCULATIONS OF LASER-ABSORPTI ON SPECTRA ON A METALLIC ATOMIC VAPOR PRODUCED BY ELECTRON-BEAM - APPLICATION TO ATOMIC VELOCITY-MEASUREMENT

We calculate the analytical shape of a laser absorption signal from th e velocity distribution of metal atoms which is fitted by a Gaussian. The neutral atoms are produced by a high evaporation rate of a liquid metallic target using a ponctual electron beam. When the absorption le ngth increases, we demonstrate that the signal evolues from a Gaussian to a hat signal. In that case, we show that we can deduce the radial atomic velocity V-R in the beam from the half-height-width value Delta nu(1/2) of the signal using the following relation V-R = lambda(0) De lta(1/2)/2 sin theta(M). If we applied this equation to experimental a bsorption signal of a gadolinium vapour, the radial velocity values ca lculated are in good agreement with those measured by a time of flight technique.