Production of long-lived atomic vapor inside high-density buffer gas

Atomic vapor of four different paramagnetic species: gold, silver, lithium, and rubidium, is produced and studied inside several buffer gases: helium, nitrogen, neon, and argon. The paramagnetic atoms are injected into the buffer gas using laser ablation. Wires with diameters 25, 50, and $100\mu \text{m}$ are used as ablation targets for gold and silver; bulk targets are used for lithium and rubidium. The buffer gas cools and confines the ablated atoms, slowing down their transport to the cell walls. Buffer gas temperatures between 20 and 295 K and densities between ${10}^{16}{\text{cm}}^{-3}$ and $2\times {10}^{19}{\text{cm}}^{-3}$ are explored. Peak paramagnetic atom densities of ${10}^{11}{\text{cm}}^{-3}$ are routinely achieved. The longest observed paramagnetic vapor density decay times are 110 ms for silver at 20 K and 4 ms for lithium at 120 K. The candidates for the principal paramagnetic-atom loss mechanism are impurities in the buffer gas, dimer formation, and atom loss on sputtered clusters.

Figure 1

The estimated scaling of Rb-He spin-relaxation cross section with temperature.

Figure 2

A schematic top view of the experimental setup.

Figure 3

(Color online) Gold-atom density decay time as a function of helium density at 295 K. The straight line is a linear fit to the low-helium-density data, where diffusion dominates the gold-atom loss. The scatter of the points is due to shot-to-shot fluctuations in the vapor production process. The inset shows the evolution of gold-atom vapor density after a single ablation shot, for helium density of $7\times {10}^{18}{\text{cm}}^{-3}$. The red line is an exponential fit to the density decay; the fitting range is from 15 to 100 ms.

Figure 4

(Color online) Silver vapor density decay time as a function of helium buffer-gas density at different temperatures.

Figure 5

(Color online) Lithium vapor density decay time as a function of helium buffer-gas density at different temperatures. The inset shows rubidium data at 295 K.