Detecting Radiation with a Supercooled Liquid

Abstract

IT is well known that if a supercooled liquid is exposed to ionizing radiation the probability of homogeneous freezing in it increases^1–3. A plausible explanation for this is that there always exist in a liquid fluctuational density variations, and at some places molecules coming close to each other form a compact microsystem—a quasi-crystallite—of a very short lifetime. The probability of formation of such quasi-crystallites increases with a lowering of temperature. In the supercooled state of a liquid this probability is large enough to render the liquid metastable with regard to freezing. These crystallites thus play the part of “embryos” for crystal growth in the liquid. The change in the Gibbs free energy for embryo formation and the molecular density variations in the liquid are then the factors which decide whether, in certain given conditions, the nucleation will take place. It can be shown that ionization significantly improves the condition for nucleation. Detailed theory for this has been worked out by us⁴ and independently by Pisarev⁵.