Available material for prolonging the decoherence time of Rb atom

We have measured the Rb atomic spin lifetime in both of paraffin-coated cell and glass cell. The experimental results shows that the lifetime of Rb atomic spin in paraffin-coated cell is about 7 ms at temperature T=50 °C, while the data in glass cell is about 20 μs, which is useful for quantum memory experiments based on atomic spin. Meanwhile, we discuss other potential materials which can be used to eliminate the inelastic collisions between alkali metal atoms and walls. Based on some experimental data and investigation, we think that BN and C₆₀H₆₀ may be the candidates.