  We present time-resolved x-ray reflectivity measurements on laser excited
coherent and incoherent surface deformations of thin metallic films. Based on a
kinematical diffraction model, we derive the surface amplitude from the
diffracted x-ray intensity and resolve transient surface excursions with
sub-Angstrom spatial precision and 70 ps temporal resolution. The novel
analysis allows for decomposition of the surface amplitude into multiple
coherent acoustic modes and a substantial contribution from incoherent phonons
which constitute the sample heating.
