High-density regime

The last formula is circumvented to the high-density total correlation density approaches rooting at their turn on the Thomas-Fermi atomic theory. Very interesting, the relation (4.477) may be seen as an atomic reflection of the (solid state) high-density regime (r < 1) given by Perdew et al. (Perdew, 1986 Wang Perdew, 1989 Seidl et al., 1999 Perdew et al., 1996) ... 

Results. This section on results will be divided in two parts. The first part concerns the high density regime (molten salts) and the second concerns the low density regime (electrolyte solutions). 

Stevens and Kremer [82-84] calculated the osmotic pressure of a system of up to 16 chains of 64 beads. Their simulation showed two scaling regimes. In the high density regime they found a scaling exponent of 9/4, characteristic of semi-dilute neutral polymer solutions. For densities below the overlap concentration, the data are consistent with a 9/8 value as predicted by Odijk s scaling theory. The simulation extended to lower densities where the noninteracting limit n = kTCp(l -I- 1/N) is reached. 

According to Kramers model, for flat barrier tops associated with predominantly small barriers, the transition from the low- to the high-damping regime is expected to occur in low-density fluids. This expectation is home out by an extensively studied model reaction, the photoisomerization of tran.s-stilbene and similar compounds [70, 71] involving a small energy barrier in the first excited singlet state whose decay after photoexcitation is directly related to the rate coefficient of tran.s-c/.s-photoisomerization and can be conveniently measured by ultrafast laser spectroscopic teclmiques. 

According to Kramers model, for flat barrier tops associated with predominantly small barriers, the transition from the low- to the high-damping regime is expected to occur in low-density fluids. This expectation is home... 

Figure 4.20. Gruneisen parameter versus pressure for different regimes are indicated. Pluses indicate properties of stishovite phase, half-filled circles and closed circles indicate properties of high-density molten material, whereas open triangles and open circles and upper branch indicate behavior of coesitelike phase (Simakov and Trunin, 1990).

The simulation data, represented in Figs. 27(a-c), confirms Eq. (57) in the region of weak /tot BN < 4) for A = 8, 16, 32 at dilute regimes whereby the values for Dq have been measured for the same system in equilibrium [20] (cf. Sec, VIIB). Substantial discrepancies emerge only for high density of the medium. 

In this section experimental results are described, which are obtained by applying the conventional pump-probe technique to m-LPPP films kept in vacuum at the temperature of liquid nitrogen [25], These results allow the identification of the primary excitations of m-LPPP and the main relaxation channels. In particular, the low and high excitation density regimes are investigated in order to get an insight into the physical processes associated with the emission line-narrowing phenomenon. 

Overall gas holdup increases with gas velocity in the dispersed bubble regime for both low and high density particle systems (Davison, 1989 Tang and Fan, 1989 Bly and Worden, 1990 Nore et al., 1992 Pottboff and Bohnet, 1993). As gas velocity increases and the system enters the coalesced and slugging regimes, the rate of increase in the overall gas holdup decreases (Bly and Worden, 1990). 

---