No abstract available

[en] Photoelectron momentum distributions from strong-field ionization of carbonyl sulfide with 800 nm central-wavelength laser pulses at various peak intensities from 4.6 to 13 × 10¹³ W cm⁻² were recorded and analyzed regarding resonant Rydberg states and photoelectron orbital angular momentum. The evaluation of the differentials of the momentum distributions with respect to the peak intensity highly suppressed the impact of focal volume averaging and allowed for the unambiguous recognition of Freeman resonances. As a result, previously made assignments of photoelectron lines could be reassigned. An earlier reported empirical rule, which relates the initial state's orbital momentum and the minimum photon expense to ionize an ac Stark shifted atomic system to the observable dominant photoelectron orbital momentum, was confirmed for the molecular target. (paper)

[en] We demonstrate a novel experimental implementation to strongly align molecules at full repetition rates of free-electron lasers. We utilized the available in-house laser system at the coherent x-ray imaging beamline at the linac coherent light source. Chirped laser pulses, i.e., the direct output from the regenerative amplifier of the Ti:Sa chirped pulse amplification laser system, were used to strongly align 2, 5-diiodothiophene molecules in a molecular beam. The alignment laser pulses had pulse energies of a few mJ and a pulse duration of 94 ps. A degree of alignment of $⟨<!--\; ???\; -->{\mathrm{c}\mathrm{o}\mathrm{s}}^2{\mathrm{\theta <!--\; ??\; -->}}_{2\mathrm{D}}⟩<!--\; ???\; -->=0.85$ was measured, limited by the intrinsic temperature of the molecular beam rather than by the available laser system. With the general availability of synchronized chirped-pulse-amplified near-infrared laser systems at short-wavelength laser facilities, our approach allows for the universal preparation of molecules tightly fixed in space for experiments with x-ray pulses. (paper)