F and F-aggregate color centers in 100 K and room temperature KCl grains irradiated with 10 keV electrons

We have conducted experiments on potassium chloride grains under temperature, pressure, and irradiation conditions comparable to planetary and astrophysical environments. These experiments are particularly relevant to the investigation of ocean worlds covered with ice shells that may contain ocean-derived salts, and which may be exposed to surface irradiation. Irradiation of sylvite (KCl) under cryogenic conditions yields trapped electrons in F and M center anion vacancies (553 nm and 819 nm respectively), whereas room temperature measurements after irradiation show additional color-center formation (R1 [675 nm], R2 [734 nm], and N [978 nm]). We attribute these additional features to the merging of F centers at higher temperatures, yielding colloids. Potassium chlorate (KClO$_3$) is identified as a possible radiolytic product resulting from modification of KCl with surficial adsorbed H$_2$O.