Fly-through relaxation excited state

Firstly, there may be a difference in the decay rates of the polarization moments bpQ of various ranks K, which is frequently the case with atoms, as was demonstrated for instance in [6, 45, 96, 135]. In order to avoid this effect, one uses well-known methods of separating the moment po, as described in Sections 2.4 and 2.5, namely using the magic angle Oo = 54.7°, or convenient linear combinations I +2I which follow from (2.29), (2.30) and the corresponding discussion. In this way we can obtain signals depending only on bPo- 

Here Maxwellian distribution of particle velocities is assumed. It can be seen that widening of the entrance slit l diminishes the role of fly-through relaxation. Substituting the expressions obtained into (2.24), it becomes possible to calculate the intensity I(t — to)- If we assume that To — Ti = 1 2 = T the expression becomes independent of the light polarization and transition type of the observation and excitation, and is quite simple  

The time dependence of such a signal is presented in Fig. 3.22. For curves 1-4 the width of the entrance slit l is five times larger than the Gaussian radius of the beam ro for curves 5-8 it is equal to it, and lower 

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