  Specular neutron reflectometry (SNR) was measured on a system of a floating
bilayer consisting of 1,2-dipalmitoyl-d62-\textit{sn}-glycero-3-phosphocholine
(d62-diC16:0PC) deposited over a
1,2-dibehenoyl-\textit{sn}-glycero-3-phosphocholine (diC22:0PC) bilayer at 25
and 55 {\deg}C. The internal structure of lipid bilayers was described by a one
dimensional scattering length density profile (SLDP) model, originally
developed for the evaluation of small angle scattering data. The corresponding
model reflectivity curves successfully describe the experimental reflectivity
curves of a supported bilayer in the gel phase and a system of a floating
bilayer in the liquid crystalline phase. The reflectivity data from the
supported bilayer were evaluated individually and served further as an input by
the data treatment of floating bilayer reflectivity curves. The results yield
internal structure of a deposited and floating bilayer on the level of
component groups of lipid molecules. The obtained structure of the floating
d62-diC16:0PC bilayer displays high resemblance to the bilayer structure in the
form of unilamellar vesicles, however, simultaneously it shows rate of
fluctuations in comparison to unilamellar vesicle bilayers.
