Laser cooling of a potassium–argon gas mixture using collisional redistribution of radiation

Abstract

We study laser cooling of atomic gases by collisional redistribution, a technique applicable to ultradense atomic ensembles at a pressure of a few hundred bars. Frequent collisions of an optically active atom with a buffer gas shift atoms into resonance with a far red detuned laser beam, while spontaneous decay occurs close to the unperturbed resonance frequency. In such an excitation cycle, a kinetic energy of the order of the thermal energy k _B T is extracted from the sample. Here we report of recent experiments investigating the cooling of a potassium–argon gas mixture, which compared to a rubidium–argon mixture investigated in earlier experiments has a smaller fine structure of the optically active alkali atoms. We observe a relative cooling of the potassium–argon gas mixture by 120 K.