Raman study of NH4CI at high pressures

Abstract

The Raman spectrum of ammonium chloride has been carefully studied in the vicinity of its Λ-transition. Spectra were recorded as a function of temperature under various fixed pressures close to 1.6 kbar, which is the pressure required to make the Λ-transition become second order. The critical exponents derivable from the spectroscopic data seem to be as reliable as those from other types of data, even in the multicritical region.