Angle-Dependent Strong Field Ionization of Oriented Carbonyl Sulfide

We have developed a method for extracting the angle-dependent single ionization probability of molecules and demonstrated it on carbonyl sulfide (OCS). The method utilizes phase-locked bi-chromatic laser fields to induce orientation via coherent rotational redistribution from non-ionizing Raman and hyper-Raman transitions, and through angle-dependent ionization. These coherent interactions create rotational wavepackets within the ionized molecules and surviving neutrals. A time-delayed intense probe pulse fragments the neutrals and ions via Coulomb explosion, and the delay-dependent S+3 yields are used to monitor the field-free evolution of the ionic and neutral rotational wavepackets. The wavepackets exhibit unique rotational revival structure near their characteristic rotational revival times. Using a model that includes the non-ionizing Raman, hyper-Raman, and angle-dependent single ionization interactions, we fit the delay-dependent evolution of the neutral and ionic wavepackets to extract the angle dependent single ionization rate. More generally, the approach should be directly applicable to measurements of the angle dependence of other strong-field processes, e.g. multiple and dissociative ionization, in molecules.