Figure 2.

Dispersion relations for (a) the CHOL sample and (b) the ASA sample, as determined from constant-q_∥ and constant-energy scans in figure 1. Three dispersion branches were observed, related to lipid molecules in gel (P_β), fluid (L_α) and liquid-ordered (l_o) patches. The CHOL dispersion in (a) is in qualitative agreement with previous reports on the collective short-wavelength dynamics in cholesterol-rich lipid membranes [42]. The meaning of the parameters α and $\hslash \omega$ in equation (2.1) are displayed in (a). The direction of constant-q_∥ and constant-energy scans is shown in (b).