The reported experimental study investigated structural transitions and configurational properties of experimentally obtained 2D strongly coupled finite clusters of size N=1−30 produced using the bidirectional electrode control arm assembly, instrument at uniform plasma parameters. Controlled laser pulses were applied to randomize the crystalline configuration and concentric shell structure of the clusters. A cooling cycle followed immediately after the laser heating cycle through synchronized shut-off of the laser beams and a completely disrupted cluster with randomly located particles (akin to a numerical simulation where grains are randomly initialized) recrystallizes to a stable configuration. The motion of the grains was continuously recorded using a top (xy) camera, and planarity was verified using a side (z) camera. For statistically reliable results and identifying the maximum number of independent crystal configurations of a cluster, many heating and cooling cycles were performed depending on the cluster size N. Video microscopy frames were processed using image analysis to extract positions and velocities of the particles, and a shell-search algorithm based on the radial distribution function was developed to automatically catalogue the crystal configurations. The probability of the occurrence of an individual crystal configuration state pk was calculated through the number of appearances of said configuration in the total number of cycles, leading to the experimental determination of configurational entropy Sc with nominal uncertainty 10%. Continuous recording of particle trajectories during shell transitions yielded insights into the energy and probability of the clusters transitioning between metastable and ground states.
Kumar et al. (Sun,) studied this question.