Collision-Induced Rovibronic Transitions in Excited States

2 Collision-Induced Rovibronic Transitions in Excited States 

When the level A = n, /p of an excited molecule M has been selectively populated by optical pumping, inelastic collisions M -h B, which occur during the lifetime Xk, will transfer M (A ) into other levels m) = u[ + An, -h A7) of the same or of another electronic state  

The difference AE = Ek — Em of the internal energies before and after the inelastic collision is transferred either into internal energy of B or into translation energy of the collisions partners. 

Molecules in the collisionally populated levels m) can decay by the emission of fluorescence or by further collisions. In the LIF spectrum new lines then appear besides the parent lines, which are emitted from the optically pumped level (Fig. 8.7). These new lines, called collision-induced satellites contain the complete information on the collision process that has generated them. Their wavelength X allows the assignment of the upper level m) = + An, 7 + A7), their intensities yield 

Optically pumped on the transition i) k) (Fig. 8.6) with a pump rate M P and collisions induce transitions A ) The rate equation for the population densi- 

Assume the upper level ) is optically pumped on the transition /) / ) 

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