Increasing the Coherence Time in a Magnetic Stimulated Raman Transition in $^{85}$Rb

We experimentally study, compare and contrast Ramsey and spin echo pulse sequence protocols in a cold $^{85}$Rb gas. Our measurements, performed in an {\em unshielded} metal vacuum canister, are dominated by laboratory noise. Both Ramsey and spin echo show a decay of the interference in about $100\, \mu $sec, while we have found that changing the axis of rotation of the echo pulse by $90^{\circ}$ can increase coherence time by nearly a factor of $10$. These results show that this new pulse sequence can be used in our system to reduce dephasing on magnetic transitions.