Pulse-shape dependence in population inversion with frequency chirping

Abstract The response of a two-level atom to an optical pulse with has a sech envelope and a tanh frequency sweep is calculated. This model is an extension of the one considered by Allen and Eberly. The model is shown to give respectable agreement, in the adiabatic and near-adiabatic limits, with the Landau-Zener formula, that gives the transition probability in the case where a constant-intensity linearly chirped radiation is assumed. This indicates that, as far as significant population inversion is concerned, the transition probability is not affected considerably by the shape of the (slowly varying) optical pulse