Depopulation strong

The CeF3 lattice absorbs strongly in the 3- to 6-fx region, and it is found that pumping in this band populates the 4/11/2 level of neodymium. Conversely, this also leads to a rapid depopulation of the same state. 

Fig. 3.9 shows the V J) and C(J) dependences for the types of transitions discussed. As can be seen for Q Q i transitions the quantum mechanical solutions already at J > 5 differ little from the J —> oo limit. At the same time, in the case ofPj. Pj.or.Pj. RI. type transitions, even at such high values as J = 50 the difference from the classical limit still constitutes a value of the order of 1% of that of the degree of polarization or of anisotropy. This may lead to considerable error if one uses classical expressions from Table 3.5 for V x) dependences of the type presented in Fig. 3.8 for the determination of parameter x Table 3.6 also presents the values of 7Z(x), P(x) and C(x) in the limit of very strong optical depopulation for x > oo- It is noteworthy that in this case the corresponding values for P-excitation are identically equal to zero, independently of J, whilst in the other cases they behave either as 1/J or as 1/J2 see Fig. 3.9. 

Equations 7-3 and 7-6 represent the two limits of molecular conductivity in a simplified useful form directly useful in real data analysis. One limit is superexchange with electron tunneling through strongly off-resonance electronic levels. The other one is hopping with successive electronic population and depopulation. By their physical nature and the form of the equations, the two modes are conceptually and physically quite different. Other systems and formal aspects are discussed in Chapter 8. 

The system of vibrational master equations has been numerically integrated with the same initial condition described in Sect. 2.3.1. Figure 15 reports the N distribution obtained in JVE with allowance for recombination at different times. One can note that at a time of 10" 3 s the N distribution with recombination is very similar to that calculated without recombination. The only part affected by recombination and by the presence of atoms is the tail of N -distribution, which is strongly overestimated in JVE without recombination (see Fig. 8). This is due to the chemical deactivation, which increases the depopulation of higher vibrational levels. These considerations suggest that the kjj values (which depend on the tail of N distribution) are smaller than the corresponding values calculated without atoms. 

One dynamical example, two-level quantum beats including decay (but not including collision induced depopulation and dephasing), illustrates the power of this complex H formalism. (See Section 6.5.3 for a detailed discussion of quantum beats in the strong coupling limit.) Consider two zero-order states, Ei = ei — iTi/2 and E2 = ei — iT2/2, where state 1 is bright and narrow and state 2 is dark and broad (T2 >> Ti). 

---