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

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

doi:10.1063/1.3194287

Cited by 149 publications

(259 citation statements)

References 73 publications

(99 reference statements)

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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%

“…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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113

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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%

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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113

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“…As a result, we can sort the resulting states of each H M i by energy and assign quantum number labels in the same order as for energy-sorted field-free states of the same symmetry. This yields a correct assignment of ''adiabatic quantum number labels'',JK aKcM , to rotational states in the field [20]. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.…”

Section: Asymmetric Topmentioning

confidence: 97%

“…The corresponding Hamiltonian matrix and the strategy of its diagonalization are described in following sections for each type of rotor. Finally, the program assigns the calculated rotational energies in the field to ''adiabatic quantum numbers'', i. e., to the adiabatically corresponding field-free rotor states [20]. To ensure correct assignments, a symmetry classification of H rot, ε and quantum states according the electric field symmetry group [21,22] is required.…”

Section: Overviewmentioning

confidence: 99%

CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields

Chang

Filsinger

Sartakov

et al. 2014

Computer Physics Communications

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a b s t r a c tThe Controlled Molecule Imaging group (CMI) at the Center for Free Electron Laser Science (CFEL) has developed the CMIstark software to calculate, view, and analyze the energy levels of adiabatic Stark energy curves of linear, symmetric top and asymmetric top molecules. The program exploits the symmetry of the Hamiltonian to generate fully labeled adiabatic Stark energy curves.CMIstark is written in Python and easily extendable, while the core numerical calculations make use of machine optimized BLAS and LAPACK routines. Calculated energies are stored in HDF5 files for convenient access and programs to extract ASCII data or to generate graphical plots are provided. Chang et al. / Computer Physics Communications 185 (2014) [339][340][341][342][343][344][345][346][347][348][349] Nature of problem: Calculation of the Stark effect of asymmetric top molecules in arbitrarily strong dc electric fields in a correct symmetry classification and using correct labeling of the adiabatic Stark curves. Program summary Solution method:We set up the full M matrices of the quantum-mechanical Hamiltonian in the basis set of symmetric top wavefunctions and, subsequently, Wang transform the Hamiltonian matrix. We separate, as far as possible, the sub-matrices according to the remaining symmetry, and then diagonalize the individual blocks. This application of the symmetry consideration to the Hamiltonian allows an adiabatic correlation of the asymmetric top eigenstates in the dc electric field to the field-free eigenstates. This directly yields correct adiabatic state labels and, correspondingly, adiabatic Stark energy curves. Restrictions:The maximum value of J is limited by the available main memory. A modern desktop computer with 16 GB of main memory allows for calculations including all Js up to a values larger than 100 even for the most complex cases of asymmetric tops. Running time:Typically 1 s-1 week on a single CPU or equivalent on multi-CPU systems (depending greatly on system size and RAM); parallelization through BLAS/LAPACK. For instance, calculating all energies up to J = 25 of indole (vide infra) for one field strength takes 1 CPU-s on a current iMac.

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“…In the current experiment (see supporting information for details) a supersonic molecular beam is used to produce a cold water sample in the gas-phase with a rotational temperature of 8 K, corresponding to > 99 % of para and > 96 % of ortho molecules in their absolute ground state, respectively. The molecular beam is then dispersed perpendicular to its flight direction according to the effective-dipole-moment- to-mass ratio (µ eff /m) using strong inhomogeneous electric fields [27,30] . Water molecules are quantum state selectively ionized via (2+1) resonance-enhanced multiphoton ionization (REMPI); a spectrum is shown in the supporting information.…”

mentioning

confidence: 99%

Separating Para and Ortho Water

et al. 2014

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Water exists as two nuclear-spin isomers, para and ortho, determined by the overall spin of its two hydrogen nuclei. For isolated water molecules the conversion between these isomers is forbidden and they act as different molecular species. Yet, these species are not readily separated and no pure para sample has been produced. Accordingly, little is known about their specific physical and chemical properties, conversion mechanisms, or interactions. Here, we demonstrate the production of isolated samples of both spin isomers in pure beams of para and ortho water in their respective absolute ground state. These single-quantum-state samples are ideal targets for unraveling spin-conversion mechanisms, for precision spectroscopy and fundamentalsymmetry-breaking studies, and for spin-enhanced applications, e. g., laboratory astrophysics and -chemistry or hypersensitized NMR experiments.Significant efforts have been undertaken to separate and study the nuclear-spin isomers of water, motivated by their importance in a wide variety of scientific disciplines. This ranges from the astronomical importance of the ortho-para ratio [1][2][3][4][5] , to studies of nuclear-spin conversion [6,7] , selection rules and reactive collisions [8][9][10] or symmetry breaking [11] . Spin-enriched samples furthermore would allow for hypersensitized NMR experiments via polarization transfer reactions [12][13][14] . However, unlike other small polyatomic molecules exhibiting spin isomerism, such as fluoromethane or ethylene [15,16] , which were spin-isomerically enriched using the light induced drift technique [7] , this has not been achieved for water. Separation through selective adsorption on surfaces was reported [17] , but these results remain controversial and could not be reproduced [18][19][20][21] . Thus, studies of spin-conversion dynamics in water have been limited to water embedded in rare gas matrices, with relative spin populations modified by the sample temperature [22] . A recent study investigated nuclear-spin conversion in the gas-phase and found no spin conversion for water monomers [23] .Recently, the production of a single spin isomer of water in a magnetic-hexapole-focuser setup was demonstrated [24] . One of the magnetically active spin projections (m = +1) of ground-state ortho water was magnetically focused into the interaction volume, while all other spin-projection states were defocused or diverged unaffected by the field. The purity of the produced ortho beam was later evaluated as 93 %, with simulations suggesting an upper limit for the achievable purity of 97 % [24,25] .Here, we experimentally demonstrate the production of pure samples of both, para and ortho water, the latter further separated into its M = 0 and M = 1 angular momentum projections, in the gas-phase. The produced single-quantum-states are ideally suited for further experiments on nuclear-spin conversion under collision-free conditions, nuclear-spin-dependent reactivity [8] , trapping of single spin-isomer samples in electromagnetic traps [26] ...

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

Cited by 149 publications

References 73 publications

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

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

CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields

Separating Para and Ortho Water

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