Detailed Refractive Index Measurement near Melting in a Plastic Crystal: Succinonitrile

Abstract

An interferometric measurement of the temperature derivative of the refractive index in succinonitrile is reported over a temperature range (30[ddot]C → 66[ddot]C) that includes melting. In pure material the behavior is clearly that of a first-order transition both on heating and on cooling. In impure material premelting effects are seen below fusion. In all cases appreciable supercooling can be observed.