Mischa Parsons

Probing Calcium Laser Excitation for Buffer Gas Chemistry

Abstract

Laser cooling of molecules such as Calcium Hydride (CaH) is a useful tool for studying physics beyond the standard model by creating ultracold H atoms. Recent laser cooling attempts have been unsuccessful due to a limited quantity of CaH in experiments. To increase the yield of CaH in reactions between Ca and H2, Rydberg (4s12s 1s0) and triplet (3P1) excitation of Ca is investigated. To assess the potential of these states, we utilized a model Calcium Hydroxide (CaOH) formation reaction. This reaction is better understood and has a lower energy threshold. Ca Rydberg excitation was attempted for the first time in a cryogenic buffer gas cell. Helium buffer gas and a water/hydrogen peroxide mixture were flowed into a cryogenic cell at temperatures of ~7K and ~160K, respectively. A solid Ca target was ablated by a pulsed neodymium-doped yttrium aluminum garnet laser and the hot gaseous plume of Ca atoms reacted with a water/hydrogen peroxide mixture. Excitation lasers at the necessary wavelengths for each Ca excitation pathway and a CaOH detection laser were directed through the cell. The transmitted signal of the detection laser was measured by a photodiode as a metric of CaOH concentration. Signal was then analyzed to determine if CaOH concentration was enhanced by the excitations. CaOH signal enhancement was observed with the triplet state. No significant enhancement was observed in Rydberg state.