Knowledge Bank

Collision-induced transitions have been investigated by microwave double resonance foe OCS in the v = 0 ground state with the M-sublevels separated by a Stark field. So far, experiments on the $(2\leftarrow 1){p} - (1 \leftarrow 0){s} $ and $(3 \leftarrow 2){p} - (1\leftarrow 0){s} $ systems have been performed for pure OCS and for mixtures with excess He, $ H_{2} $ and $CH3OH$. For the $(2 \leftarrow 1){p} - (1 \leftarrow 0){s} $ four-level system with $ M_{p} = 1 $ and $ M_{s} = 0$, parity-changing (dipolar) $\Delta M=1$ transitions are preferred in OCS collisions with the dipolar gases OCS and $CH_{3} $OH, while parity-conserving (nondipolar) $\Delta M=1$ transitions are preferred in collisions with He and $ H_{2} $. For the $(3 \leftarrow 2){p} - (1\leftarrow 0){s} $ system with $M_{p} = 2 $ and $ M_{s} = 0 $, signals are seen for all collision partners corresponding to a parity-conserving $\Delta M = 2 $ preference. For $ M_{p} = 0$ and $ M_{s} = 0 $, parity-changing $\Delta M=0$ transitions are preferred in collisions with OCS and $ CH_{3}OH,$ while parity-conserving $\Delta M=0$ transitions are preferred for He and $ H_{2} $.