Countering collisional effects

In particular, we reconsider the bichroraatic control scenario discussed in Section 3.1.1, assiuning, however, that the molecules are in solution at temperature T. Further, we irradiate the system so as to saturate the ,) to E2) transition and simultaneously photodissociate the system. 

The initial state, prior to dissociation, is a mixed EX), E2) state described, in the energy representation, by a 2 x 2 density matrix with elements p, , (ij = 1,2). Photodissociation of this mixed state can be written as a generalization [175] of Eq. (3.12). In Eq. (3.12) we assumed an initial state of the form of Eq. (5.9) (with k = 1,2), so that the corresponding density matrix would be Eq. (5.11). Hence, Eq. (3.12) could be rewritten as 

Equation (5.18) is, in fact, the correct generalization to the case where the initial state is mixed and is represented by pt j. Below we neglect the z dependence in e, replacing it by e [see Eq. (2.9)]. 

Here we have recognized that the quantity R3 relaxes to the thermodynamic population difference R at temperature T, with  

Consider then excitation of this mixed state with a Gaussian pulse, within the rotating wave approximation. The pulse is of the form 

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