Laser-Induced Alignment and Orientation of Quantum-State-Selected Large Molecules

Holmegaard, Lotte; Nielsen, Jens Hedegaard; Nevo, Iftach; Stapelfeldt, Henrik; Filsinger, Frank; Küpper, Jochen; Meijer, Gerard

doi:10.1103/physrevlett.102.023001

Cited by 303 publications

(357 citation statements)

References 24 publications

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“…Finally, the TOF spectra, which indicate the degree of orientation, show a backward-forward asymmetry of 58/42 ( Figure 6 e) for the undeflected molecules, which increases to 67/33 ( Figure 6 f) for the deflected molecules. In summary, even when the intensity of the YAG alignment pulse is lowered by an order of magnitude a strong degree of 3D alignment and orientation is maintained, in accordance with previous findings for 1D alignment and orientation [21,23].…”

Section: Alignment and Orientation At Low Laser Intensitysupporting

confidence: 92%

“…As suggested by Friedrich and Herschbach a decade ago [16,17], and later demonstrated experimentally [10,[18][19][20][21], orientation can be added to alignment by combining the strong laser field with a weak static electric field. Therefore, we use 1D orientation to denote 1D alignment and, simultaneously, a preferred direction of the permanent dipole moment.…”

Section: Introductionmentioning

confidence: 99%

“…Optimizing the degree of orientation in the mixed laser and static electric field method imposes, however, an even stronger requirement on the initial rotational state distribution. Recently, we showed that 1D orientation, using the mixed-field method, can be strongly enhanced by using rotational-quantum-state selected molecules as targets [21,23]. The state selection is obtained by passing arXiv:0906.2971v2 [physics.chem-ph] 4 Aug 2009 a cold molecular beam through an electrostatic deflector that spatially disperses molecules according to their rotational quantum state.…”

Section: Introductionmentioning

confidence: 99%

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

Nevo

Holmegaard

Nielsen

et al. 2009

Phys. Chem. Chem. Phys.

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109

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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. 36.40.Wa

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Section: Alignment and Orientation At Low Laser Intensitysupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

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Holmegaard

Nielsen

et al. 2009

Phys. Chem. Chem. Phys.

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109

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“…In this case, a narrow angular peak is expected in molecular scattering, whose position is controllable by inclination of the plane of rotation with respect to the deflecting field [35]. Laser prealignment may be used to manipulate molecular deflection by inhomogeneous static fields as well [36] (for recent exciting experiments on post-alignment of molecules scattered by static electric fields see [37]). In particular, one may affect molecular motion in relatively weak fields that are insufficient to modify rotational states by themselves.…”

Section: Discussionmentioning

confidence: 99%

Controlling molecular scattering by laser-induced field-free alignment

Gershnabel

Averbukh

2010

Phys. Rev. A

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We consider deflection of polarizable molecules by inhomogeneous optical fields, and analyze the role of molecular orientation and rotation in the scattering process. It is shown that molecular rotation induces spectacular rainbow-like features in the distribution of the scattering angle. Moreover, by preshaping molecular angular distribution with the help of short and strong femtosecond laser pulses, one may efficiently control the scattering process, manipulate the average deflection angle and its distribution, and reduce substantially the angular dispersion of the deflected molecules. We provide quantum and classical treatment of the deflection process. The effects of strong deflecting field on the scattering of rotating molecules are considered by the means of the adiabatic invariants formalism. This new control scheme opens new ways for many applications involving molecular focusing, guiding and trapping by optical and static fields.

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“…Only the last method has been experimentally demonstrated on OCS 9,27 and on HXeI (ref. 28) and iodobenzene 29 molecules. The degree of orientation that can be achieved very sensitively depends on the rotational temperature of the molecular sample.…”

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confidence: 99%

Impulsive orientation and alignment of quantum-state-selected NO molecules

et al. 2009

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Manipulation of the molecular-axis distribution is an important ingredient in experiments aimed at understanding and controlling molecular processes 1-6 . Samples of aligned or oriented molecules can be obtained following the interaction with an intense laser field 7-9 , enabling experiments in the molecular rather than the laboratory frame 10-12 . However, the degree of impulsive molecular orientation and alignment that can be achieved using a single laser field is limited 13 and crucially depends on the initial states, which are thermally populated. Here we report the successful demonstration of a new technique for laser-field-free orientation and alignment of molecules that combines an electrostatic field, non-resonant femtosecond laser excitation 14 and the preparation of state-selected molecules using a hexapole 2 . As a unique quantum-mechanical wavepacket is formed, a large degree of orientation and alignment is observed both during and after the femtosecond laser pulse, which is even further increased (to cos θ = −0.74 and cos 2 θ = 0.82, respectively) by tailoring the shape of the femtosecond laser pulse. This work should enable new applications such as the study of reaction dynamics or collision experiments in the molecular frame, and orbital tomography 11 of heteronuclear molecules.The outcome of molecular collision experiments is strongly affected by the angular anisotropies in the initial molecular axis distribution. In bimolecular and molecule-surface collisions, collision cross-sections sensitively depend on the relative arrangement of the collision partners 1,2 . Likewise, photon-molecule collisions such as X-ray diffraction and photodissocation experiments aimed at the elucidation of molecular structure or photochemical activity depend on and can benefit from angular confinement of the sample 3,4 . The two most important moments of the molecular axis distribution are the 'alignment' ( cos 2 θ ) and 'orientation' ( cosθ ), where θ is the angle between the molecular axis and a reference axis.First attempts to orient and align molecules relied on electrostatic fields. A hexapole electric field can be used to stateselect polar molecules and orient them through their first-order Stark effect 2,5 using a moderate field strength. The orientation is limited by the selected state. 'Brute-force orientation' uses a strong homogeneous electrostatic field and relies on the second-and higher-order Stark effect 6 . It requires molecules with a large dipole moment and extremely high electric-field strengths.As a part of extensive efforts aimed at achieving laser-controlled chemistry 15-17 , laser-controlled alignment 8 has attracted considerable attention. Suitably chosen laser fields can exert torques on molecules, exploiting the interaction of the laser field with the molecular polarizability. Both adiabatic alignment, where molecules are exposed to a slowly varying laser field 18 , and non-adiabatic (impulsive) alignment, where molecules align after receiving a kick by a short laser pulse 7 , have been succe...

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Laser-Induced Alignment and Orientation of Quantum-State-Selected Large Molecules

Cited by 303 publications

References 24 publications

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

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

Controlling molecular scattering by laser-induced field-free alignment

Impulsive orientation and alignment of quantum-state-selected NO molecules

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