Spectral line shape in open-source atomic beam laser spectroscopy experiments

The line shape in atomic beam laser spectroscopy experiments has been calculated for an atomic beam emitted from an open filament and propagated into the vacuum under collisionless conditions. It is shown that the activation energy the atoms have to overcome in order to leave the sample leads to significant deviations from the Voigt line shape. The unreliable application of the Voigt profile under the conditions specified above leads to an overestimate of the line width by up to 70%. A modified Voigt profile is given, which has proved a reliable capability to describe the line shape under the above mentioned conditions.