Abstract The probabilities of the two‐photon absorption by a biexciton in the ground and the first vibrational states in CuBr and the probability of the two‐photon Raman scattering with the participation of the ground and the first vibrational states of the biexciton as intermediate states are calculated by perturbation theory method. Supposing that a Lorentzian distribution of frequencies ωi of the exciting light and a Lorentzian shape of the emission lines of the excition occur, the shape of the emission line at different values of the biexciton half‐width Γm is calculated. The dependence of the Raman scattering maximum position on ωi is obtained. At the condition 2Γ ≧ Γm; Γ Γm ≦ Γf the experimentally observed deviation of the Raman scattering maximum shifting from 2Δωi, is explained. The polarizational properties of the Raman scattering probability are obtained including the case when the intermediate states are the biexcitons Γ1, Γ5, Γ3.
We present a theoretical and experimental study of the line shape of resonant four-wave mixing induced by broad-bandwidth laser radiation that revises the theory of Meacher, Smith, Ewart, and Cooper (MSEC) [Phys. Rev. A 46, 2718 (1992)]. We adopt the same method as MSEC but correct for an invalid integral used to average over the distribution of atomic velocities. The revised theory predicts a Voigt line shape composed of a homogeneous, Lorentzian component, defined by the collisional rate \ensuremath{\Gamma}, and an inhomogeneous, Doppler component, which is a squared Gaussian. The width of the inhomogeneous component is reduced by a factor of \ensuremath{\surd}2 compared to the simple Doppler width predicted by MSEC. In the limit of dominant Doppler broadening, the width of the homogeneous component is predicted to be 4\ensuremath{\Gamma}, whereas in the limit of dominant homogeneous broadening, the predicted width is 2\ensuremath{\Gamma}. An experimental measurement is reported of the line shape of the four-wave-mixing signal using a broad-bandwidth, ``modeless,'' laser resonant with the
Q1(6) line of the A
2\ensuremath{\Sigma}-X
2\ensuremath{\Pi}(0,0) system of the hydroxyl radical. The measured widths of the Voigt components were found to be consistent with the predictions of the revised theory. \textcopyright{} 1996 The American Physical Society.