Local-Field Effects on Spontaneous Emission in a Dense Supercritical Gas

We present results of experiments on the spontaneous emission rate of a europium complex in dense supercritical ${\mathrm{CO}}_2$. The refractive index of the supercritical gas is varied from 1.00 to 1.27 by increasing the pressure up to a 1000 bars. Accordingly, the spontaneous emission rate changes. Local-field effects on spontaneous emission are clearly observed in these experiments. The empty-cavity model for the spontaneous emission rate inside dielectrics is confirmed.