Reaching optimally oriented molecular states by laser kicks

We present a strategy for postpulse molecular orientation aiming both at efficiency and maximal duration within a rotational period. We first identify the optimally oriented states which fulfill both requirements. We show that a sequence of half-cycle pulses of moderate intensity can be devised for reaching these target states.

Figure 1

Maximal orientation efficiency (crosses) and associated duration (open circles) as a function of $N$, where $N+1$ is the dimension of the rotationally excited subspace ${\mathcal{H}}_0^{\left(N\right)}$ (see text). The solid and dashed lines are just to guide the lecture.

Figure 2

Orientation dynamics during the train of HCPs at $T=0\mathrm{K}$: panel (a) for $⟨\psi \left(s\right)\mid \cos \theta \mid \psi \left(s\right)⟩$ and panel (b) for ${\mid ⟨{\chi }_0^{\left(4\right)}\mid \psi \left(s\right)⟩\mid }^2$. The solid line corresponds to $\mid \psi \left(s\right)⟩$ calculated exactly and the dashed line to the wave function propagated in the subspace ${\mathcal{H}}_0^{\left(4\right)}$. The train of HCPs is displayed on panel (b) and the optimal orientation is indicated by a horizontal line on panel (a).

Figure 3

Postpulse orientation dynamics of the molecule LiCl after interaction with a train of HCPs (the time $t=0$ corresponds to the first kick) in the case $A=1$, $T=0\mathrm{K}$ [panel (a)] and $A=2$, $T=5\mathrm{K}$ [panel (b)]. Solid and dashed lines correspond respectively, to the averages calculated with the exact wave function and the optimal state [$\mid {\chi }_0^{\left(4\right)}⟩$ on panel (a) and ${\rho }^{\left(7\right)}$ on panel (b)].