Melting criteria and imaging spectroradiometry in laser-heated diamond-cell experiments

As a step toward resolving current discrepancies among ultrahigh-pressure melting curves obtained with the laser-heated diamond cell, we critically evaluate two aspects of the experiments that require further examination: (i) the criteria used to detect that melting has taken place, and (ii) the methods employed for measuring spatially variable temperatures. A review of recent efforts illustrates how defining reliable melting criteria remains problematical in many experiments, whereas current and prospective advances in imaging spectroradiometry can yield robust methods for determining the temperature distribution within the laser-heated diamond cell.