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We are developing at PBFA II a laser-reflection-holographic-interferometer technique to measure the time- and space-resolved hydrodynamic response of planar targets to intense light-ion-beam energy deposition. The interpretation of these experiments will lead to an improved understanding of ion beam divergence. A linear analysis of thermoelastic response indicates that ion beam spatial and temporal profiles (including filamentation), as well as properties of the high-temperature ablation plasma, can be obtained from such experiments. For PBFA II we have used the hydrodynamic code TITAN to design the experiments. Single crystals of Al[sub 2]O[sub 3] will be employed initially as targets, since their high Hugoniot elastic limit of ∼200 kbar will permit an elastic wave analysis. Single crystals of LiF will be used at energy deposition levels corresponding to megabar pressures. We will discuss the theory, previous electron beam, and planar plate impact experiments which have employed the diagnostic technique, advantages of arranging the Al[sub 2]O[sub 3] and LiF as shock wave window materials, possible limitations on the technique, and PBFA-II results. This work was supported by U.S. DOE contract No. DE-AC04-76DP00789. [ABSTRACT FROM AUTHOR]