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The journal of physical chemistry / A 124(40), 8341-8345 (2020). doi:10.1021/acs.jpca.0c05893 special issue: "Daniel Neumark Festschrift", Methyl vinyl ketone (C$_4$H$_6$O) is a volatile, labile organic compound of importance in atmospheric chemistry. We prepared a molecular beam of methyl vinyl ketone with a rotational temperature of 1.2(2) K and demonstrated the spatial separation of the s-cis and s-trans conformers of methyl vinyl ketone using the electrostatic deflector. The resulting sample density was 1.5(2) × 10$^8$ cm$^{−3}$ for the direct beam in the laser ionization region. These conformer-selected methyl vinyl ketone samples are well suited for conformer-specific chemical reactivity studies such as in Diels−Alder cycloaddition reactions., Published by Soc., Washington, DC

Journal of molecular structure 1208, 127863 (2020). doi:10.1016/j.molstruc.2020.127863 special issue: "VSI: Jon Hougen.", The spatial separation of 2-propanol monomer from its clusters in a molecular beam by an electrostatic deflector was demonstrated. Samples of 2-propanol monomer with a purity of 90% and a beam density of $7 \times 10^6$ cm$^{-3}$ were obtained. These samples were utilized to study the femtosecond-laser-induced strong-field multi-photon ionization and fragmentation of 2-propanol using non-resonant 800 nm light with peak intensities of $3–7 \times 10^{13}$ W/cm$^2$., Published by Elsevier, New York, NY [u.a.]

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. The production of isolated samples of both spin isomers is demonstrated 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 fundamental symmetry-breaking studies, and for spin-enhanced applications, for example laboratory astrophysics and astrochemistry or hypersensitized NMR experiments.

Wasser existiert in Form zweier Kernspinisomere, para und ortho, definiert durch den Gesamtspin der zwei Wasserstoffatomkerne. In isolierten Wassermolekülen ist die Umwandlung zwischen den beiden Isomeren quantenmechanisch verboten, und sie können als zwei verschiedene Molekülspezies betrachtet werden. Ihre Trennung ist nicht trivial, und reine Proben von para-Wasser sind bisher nicht erzeugt worden. Daher sind die physikalischen und chemischen Eigenschaften, Umwandlungsmechanismen und Wechselwirkungen der beiden Isomere kaum bekannt. Hier demonstrieren wir die Isolierung beider Spinisomere in reinen Molekülstrahlen von para- und ortho-Wasser im jeweiligen absoluten Grundzustand. Die Moleküle in einzelnen Quantenzuständen sind ideale Proben für Studien zu Umwandlungsmechanismen der Isomere, für Präzisionsspektroskopie, zur Untersuchung fundamentaler physikalischer Symmetriebrechung sowie für kernspinbasierte Anwendungen, z. B. Laborexperimente zur Astrophysik und -chemie oder hochempfindliche NMR-Experimente.

We experimentally demonstrated strong adiabatic mixed-field orientation of carbonyl sulfide molecules (OCS) in their absolute ground state of $\text{N}_{\text{up}}/\text{N}_{\text{tot}}=0.882$. OCS was oriented in combined non-resonant laser and static electric fields inside a two-plate velocity map imaging spectrometer. The transition from non-adiabatic to adiabatic orientation for the rotational ground state was studied by varying the applied laser and static electric field. Above static electric field strengths of 10 kV/cm and laser intensities of $10^{11} \text{W/cm}^2$ the observed degree of orientation reached a plateau. These results are in good agreement with computational solutions of the time-dependent Schr\"odinger equation., Comment: 9 pages, 5 figures

We have developed and experimentally demonstrated an improved electrostatic deflector for the spatial separation of molecules according to their dipole-moment-to-mass ratio. The device features a very open structure that allows for significantly stronger electric fields as well as for stronger deflection without molecules crashing into the device itself. We have demonstrated its performance using the prototypical OCS molecule and we discuss opportunities regarding improved quantum-state-selectivity for complex molecules and the deflection of unpolar molecules., 6 figures

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. The production of isolated samples of both spin isomers is demonstrated 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 fundamental symmetry-breaking studies, and for spin-enhanced applications, for example laboratory astrophysics and astrochemistry or hypersensitized NMR experiments.

Many molecules exhibit multiple rotational isomers (conformers) that interconvert thermally and are difficult to isolate. Consequently, a precise characterization of their role in chemical reactions has proven challenging. We have probed the reactivity of specific conformers using an experimental technique based on their spatial separation in a molecular beam by electrostatic deflection. The separated conformers react with a target of Coulomb-crystallized ions in a trap. In the reaction of Ca$^+$ with 3-aminophenol, we find a twofold larger rate constant for the \textit{cis}- compared to the \textit{trans}-conformer (differentiated by the O-H bond orientation). This result is explained by conformer-specific differences in the long-range ion-molecule interaction potentials. Our approach demonstrates the possibility of controlling reactivity through selection of conformational states., Comment: 3 figures

Review of scientific instruments 89(9), 096110 (2018). doi:10.1063/1.5026145, A knife edge for shaping a molecular beam is described to improve the spatial separation of the species in a molecular beam by the electrostatic deflector. The spatial separation of different molecular species from each other as well as from atomic seed gas is improved. The column density of the selected molecular-beam part in the interaction zone, which corresponds to higher signal rates, was enhanced by a factor of 1.5, limited by the virtual source size of the molecular beam., Published by American Institute of Physics, [S.l.]