Thermally induced coloration of KBr at high pressures

Laser-heated diamond-anvil cell (LHDAC) experiments reveal electronic changes in KBr at pressures between similar to 13-81 GPa when heated to high temperatures that cause runaway heating to temperatures in excess of similar to 5000 K. The drastic changes in absorption behavior of KBr are interpreted as rapid formation of high-pressure F-center defects. The defects are localized to the heated region and thus do not change the long-range crystalline order of KBr. The results have significant consequences for temperature measurements in LHDAC experiments and extend the persistence of F centers in alkali halides to at least 81 GPa.