- In order to verify the predictions of the 2D high Atwood number potential flow model for the evolution of the shock wave induced Richtmyer-Meshkov instability,(1) shock-tube experiments were performed with a single-mode perturbation and two competing bubbles as the initial conditions.(2) The experimental results were compared to theoretical model and to numerical simulation. In the present work the dependence of the instability on the Atwood number and the dimensionality of the instability were investigated in a shock tube apparatus. A high speed schlieren photography system were used to monitor the evolution of the unstable contact surface. Different Atwood numbers were achieved by using different gases. The results of those experiments were found to be in very good agreement with the predictions of theoretical model and numerical simulation. These results verify the key elements of the Atwood number scaling of the bubble-merger model used for the prediction of the multi-mode bubble and spike front evolution at all Atwood numbers. The dimensionality investigation of the instability evolution was done using a pyramid like initial perturbation. The results reveal the same two key elements of the bubble-merger model to describe the bubble and spike front evolution as in the 2D case(2) except for different scaling constants.