Laser-induced 3D alignment and orientation of quantum-state-selected molecules

A strong inhomogeneous static electric field is used to spatially disperse a rotationally cold supersonic beam of 2,6-difluoroiodobenzene molecules according to their rotational quantum state. The molecules in the lowest lying rotational states are selected and used as targets for 3-dimensional alignment and orientation. The alignment is induced in the adiabatic regime with an elliptically polarized, intense laser pulse and the orientation is induced by the combined action of the laser pulse and a weak static electric field. We show that the degree of 3-dimensional alignment and orientation is strongly enhanced when rotationally state-selected molecules, rather than molecules in the original molecular beam, are used as targets.Comment: 8 pages, 7 figures; v2: minor update

Quantum-state selection, alignment, and orientation of large molecules using static electric and laser fields

Supersonic beams of polar molecules are deflected using inhomogeneous electric fields. The quantum-state selectivity of the deflection is used to spatially separate molecules according to their quantum state. A detailed analysis of the deflection and the obtained quantum-state selection is presented. The rotational temperatures of the molecular beams are determined from the spatial beam profiles and are all approximately 1 K. Unprecedented degrees of laser-induced alignment $(=0.972)$ and orientation of iodobenzene molecules are demonstrated when the state-selected samples are used. Such state-selected and oriented molecules provide unique possibilities for many novel experiments in chemistry and physics.Comment: minor changes, references update

LASER-INDUCED ALIGNMENT AND ORIENTATION OF QUANTUM-STATE-SELECTED LARGE MOLECULES

H. Stapelfeldt and T. Seideman, \textit{Rev.~Mod.~Phys.L. Holmegaard et al., \textit{Phys.~Rev.~Lett.Author Institution: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195; Berlin, Germany; Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, DenmarkFor many experiments in chemistry and physics, i.\,e., reactive scattering, X-ray or electron diffraction experiments, a high level of control over the spatial orientation of molecules would be very beneficial. It is well known that molecules can be aligned and oriented in space using strong dc electric fields or laser pulses.~, \textbf{75}, (2003), 543} Here, we demonstrate that the degree of laser-induced alignment and orientation can be considerably improved, if quantum state selected samples are used.~, \textbf{102}, (2009), 023001} A strong inhomogeneous electric field is used in a Stern-Gerlach-type experiment to disperse iodobenzene molecules in a supersonic jet according to their rotational quantum state. Molecules in the lowest rotational quantum states are deflected most and can be used as targets for further experiments. This method is widely applicable to all, small and large, polar molecules and should eventually enable experiments on pure samples of strongly aligned or oriented ground-state molecules offering new prospects in molecular sciences

SPATIALLY SEPARATING STRUCTURAL ISOMERS OF NEUTRAL MOLECULES

L. Holmegaard et al., \textit{Phys.~Rev.~Lett.F. Filsinger et al., \textit{Phys.~Rev.~Lett.Author Institution: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195; Berlin, Germany; Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, DenmarkLarge (bio)molecules exhibit multiple conformers (structural isomers), even under the cold conditions present in a supersonic jet. For various applications, i.\,e., scattering experiments or time resolved studies, it would be highly desirable to prepare molecular packets of individual conformers. It is well known that polar molecules can be manipulated using strong electric fields. Recently, we have demonstrated that electrostatic deflection of a molecular beam can be used for quantum-state selection of large molecules.~, \textbf{102}, (2009),023001 } Here, we demonstrate how this quantum state selectivity can be exploited to spatially separate the individual conformers of large molecules based on their distinct mass-to-dipole moment (m/$\mu$) ratios. In a proof-of-principle experiment, we have spatially isolated both, cis and trans, conformers of 3-aminophenol. We will compare this approach to conformer selection using alternating gradient (dynamic) focusing in an m/$\mu$-selector.~ \textbf{100}, (2008),133003