Anomalously high intensity of the impurity-exciton lines indicate their giant oscillator strength of about f _ i \ sim10 per impurity center while the oscillator strength of free excitons is only of about f _ { \ rm ex } \ sim10 ^ {-4 } per unit cell.
22.
Therefore, the ratio m / m ^ * of the free electron mass m to its effective mass m ^ * in a crystal can be considered as the oscillator strength for the transition of an electron from the quantum state at the bottom of the n band into the same state.
23.
An important prediction of Pekar theory is violation of the Kramers-Kronig relation in polariton resonances because the real part of dielectric function is controlled by the oscillator strength of polariton transition ( or the splitting between the upper and lower polariton branches ) while the imaginary part of it by the decay of polaritons.
24.
For scaling systems such as Rydberg atoms in strong fields, the Fourier transform of an oscillator strength spectrum computed at fixed \ epsilon as a function of w is called a recurrence spectrum, because it gives peaks which correspond to the scaled action of closed orbits and whose heights correspond to D ^ i _ { \ it nk }.
25.
During 1985-1987 Tsu served as the amorphous silicon program group leader at the National Renewable Energy Laboratory ( then known as SERI, Solar Energy Research Institute ) in Golden, CO . His theoretical derivation of the relationship between the optical absorption and disorder in amorphous silicon and germanium in terms of fundamental constants shows that the slope of the Tauc plot is uniquely determined by the oscillator strength of the transition, the deformation potential and the mean deviation of the atomic coordinates obtained from the RDF.
26.
Therefore for large excitons in direct-gap crystals the oscillator strength f _ { \ rm ex } of exciton absorption is proportional to | \ Phi _ { \ rm ex } ( 0 ) | ^ 2 which is the value of the square of the wave function of the internal motion inside the exciton \ Phi _ { \ rm ex } ( \ boldsymbol { r } _ e-\ boldsymbol { r } _ h ) at coinciding values of the electron \ boldsymbol { r } _ e and hole \ boldsymbol { r } _ h coordinates.
