Diffusion-broadened line shape near a turning point
Shapiro D.A., Stepanov M.G.
PACS: 32.70.Jz, 42.55.Ye, 52.20.Hv
An absorption spectrum of the gas with large Doppler width and soft collisions between particles is studied. Particles are assumed having a nonlinear dependence of the resonance frequency on velocity. The shape of the narrow peak in the spectrum resulting from an extreme point of this dependence is calculated analytically for the first time. Without collisions it has the characteristic asymmetric shape. Collisions are shown to broaden the line and change its shape. The profile of probe-field spectrum in a three-level system with the strong field at adjacent transition is obtained. Components of Autler Townes doublet are found to spread and repel each other because of collisions.