Broadening inhomogeneous critical

We have also another interest in the fluid near the critical density. Near the critical density, there is a developed local structure around the solute molecule, which is also spectroscopically observable. If the relaxation time of the local structure is slow enough, we could see some density effect on the ground state hole broadening process just after the excitation, since this process is related to the relaxation of inhomogeneity. 

Figure 2 shows the transient absorption spectrum of PB in CI%H at 5.7 MPa. The pattern of the transient sp>ectrum is almost the same as those in methanol. The hole broadening occurs mostly within 0.8 ps, and the bleach is recovered with two different time constants in a similar manner as in the liquid solvents, although the recovery after 2 ps is much slower in the fluid near the critical density (about 40 ps). It is also to be noted that the bleach signal after 2 ps is narrow banded in comparison with the equilibrium absorption. This can be interpreted by the overlapping of the excited state absorption, and/or, the small inhomogeneity remained after 2 ps due to the long time density fluctuation. 

Fig. 17. Schematic of the nonadecane/urea-inclusion compound. From left to right single-crystal experiment by rotation around the channel axis. Critical inhomogeneous linebroadening on approaching the transition temperature from above, with a lineshape invariant by rotation around c hole burning in the last spectrum proves the inhomogeneous nature of the broadening. Schematic of rotation patterns that gives the chain orientation in the low-temperature phase.

Therefore the radiospectroscopy can be considered as a sensitive tool for the size effects investigation in nanomaterials. The theoretical base for above methods application is the description of radiospectroscopy spectra peculiarities due to above size effects with respect to the characteristic features of a nanomaterial. In particular, the disappearance of spontaneous polarization at critical size in ferroelectric nanomaterial should lead to the variation of the spectrum symmetry, while the distribution of the nanoparticle sizes have to result in the inhomogeneous resonance lines broadening. 

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