 It was also explicitly assumed that spontaneous emission is described by an exponential decay of the coefficient formula_10 with decay constant formula_11.formula_12 is the (generalized) Rabi frequency, which is 
where formula_14 is the detuning and measures how far the light frequency, formula_15, is from the transition, formula_16.formula_17 where formula_18 is the transition dipole moment for the formula_19 transition and formula_20 is the vector electric field amplitude including the polarization.