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Abstract Controlling the internal quantum states of chiral molecules for a selected enantiomer has a wide range of fundamental applications from collision and reaction studies, quantum information to precision spectroscopy. Achieving full enantiomer-specific state transfer is a key requirement for such applications. Using tailored microwave fields, a chosen rotational state can be enriched for a selected enantiomer, even starting from a racemic mixture. This enables rapid switching between samples of different enantiomers in a given state, holding great promise, for instance, for measuring parity violation in chiral molecules. Although perfect state-specific enantiomeric enrichment is theoretically feasible, achieving the required experimental conditions seemed unrealistic. Here, we realize near-ideal conditions, overcoming both the limitations of thermal population and spatial degeneracy in rotational states. We achieve over 92% enantiomer-specific state transfer efficiency using enantiopure samples. This indicates that 96% state-specific enantiomeric purity can be obtained from a racemic mixture, in an approach that is universally applicable to all chiral molecules of C 1 symmetry. Our work integrates the control over internal quantum states with molecular chirality, thus expanding the field of state-selective molecular beams studies to include chiral research.

We report a combined experimental and theoretical study on the influence of microwave pulse durations on enantiomer-specific state transfer. Two triads of rotational states within a chiral molecule (1-indanol) are selected to address the possible scenarios. In the triad connected to the absolute ground state, the simplest triad that exists for all chiral molecules, the enantiomer-specific state transfer process simplifies into a sequence of two-level transitions. The second triad, including higher rotational states, represents a more generic scenario that involves multiple Rabi frequencies for each transition. Our study reveals that the conventional $\frac{\pi}{2}-\pi-\frac{\pi}{2}$ pulse sequence is not the optimal choice, except for the ideal case when in the simplest triad only the lowest state is initially populated. We find that employing a shorter duration for the first and last pulse of the sequence leads to significantly higher state-specific enantiomeric enrichment, albeit at the expense of overall population in the target state. Our experimental results are in very good agreement with theory, substantiating the quantitative understanding of enantiomer-specific state transfer.

Glycolipids are glycoconjugates with important biological functions, but techniques for their analysis are deficient. Here, the authors report the use of cryogenic gas-phase infrared spectroscopy to investigate isomerism in a set of immunologically relevant glycolipids, and show that their structural features can be accurately resolved based on a narrow spectral fingerprint region.

Abstract Motivation The spectroscopy of diatomic molecules is an important research area in chemical physics due to its relevance in astrochemistry, combustion chemistry, and ultracold physics. However, there is currently no database where the user can easily retrieve, in a useful format, the spectroscopic constants of a given molecule. A similar situation appears concerning the vibrational Franck–Condon factors for diatomic molecules, a crucial parameter to infer laser cooling prospects for molecules. To address this problem, and inspired by the idea that data should be open and freely accessible, we have developed a user-friendly website ( https://rios.mp.fhi.mpg.de ) where the user can retrieve spectroscopic constants and Franck–Condon factors in useful formats. Implementation In this database, the spectroscopic constants of the ground states and first excited states of the diatomic molecules are accessible from the website and can be retrieved in readable formats. The website is implemented within the LAMP web service stacks. In particular, using Linux as the operative system, Apache as the HTTP Server, MySQL as the database management system, and PHP as the programming language for the web. Furthermore, the user can register and upload new data. This project is licensed under the Free-Libre/Open Source Software (FLOSS) license Apache License 2.0 which allows free and open access to the codes as well as efficient collaboration in the maintenance of the software. Conclusions and impact The present data-driven website presents essential information in a user-friendly manner and may help the chemical physics community to identify molecules that should be explored through spectroscopic techniques.

We present absolute frequency measurements of the ^{1}P_{1}←^{1}S_{0} (229-nm) and ^{3}P_{1}←^{1}S_{0} (326-nm) transitions for all naturally occurring isotopes of cadmium. The isotope shifts and hyperfine intervals of the fermionic isotopes are determined with an accuracy of 3.3 MHz. We find that quantum interference in the laser-induced fluorescence spectra of the ^{1}P_{1}←^{1}S_{0} transition causes a variation of up to 29(5) MHz in determining the hyperfine splitting when not accounted for with an appropriate model. Using a King-plot analysis, we extract the field- and mass-shift parameters and determine nuclear charge radius differences for the fermions. The lifetime of the ^{1}P_{1} state is determined to be 1.60(5) ns by measuring the natural linewidth of the ^{1}P_{1}←^{1}S_{0} transition. These results resolve significant discrepancies among previous measurements.

Abstract Prompted by the centenary of Alfred Landé's g‐factor, we reconstruct Landé's path to his discovery of half‐integer angular momentum quantum numbers and of vector coupling of atomic angular momenta—both encapsulated in the g‐factor—as well as point to reverberations of Landé's breakthroughs in the work of other pioneers of quantum physics.

Glycosyl cations are key intermediates in glycosylation reactions, but their structure has remained elusive due to their transient nature. Here, the authors perform an in-depth structural analysis and report that C2-participating protective groups induce acetoxonium cations with distinct ring conformations.

A novel traveling-wave Zeeman decelerator based on a double-helix coil geometry capable of decelerating paramagnetic molecules with high efficiency is presented. Moving magnetic traps are generated by applying time-dependent currents through the decelerator coils. Paramagnetic molecules in low-field-seeking Zeeman states are confined inside the moving traps which are decelerated to lower forward velocities. As a prototypical example, we demonstrate the deceleration of OH radicals from an initial velocity of 445 m s ^−1 down to various final velocities. The experimental results are analyzed and numerically reproduced with the help of trajectory simulations confirming the phase-space stability and efficiency of the deceleration of the molecules in the new device.

The concept of a novel traveling wave Zeeman deccelerator based on a double-helix wire geometry capable of decelerating paramagnetic species with high efficiency is presented. A moving magnetic trap is created by running time-dependent currents through the decelerator coils. Paramagnetic species in low-field-seeking Zeeman states are confined in the moving traps and transported to the end of the decelerator with programmable velocities. Here, we present the theoretical foundations underlying the working principle of the traveling-trap decelerator. Using trajectory simulations, we characterise the performance of the new device and explore the conditions for phase-space stability of the transported molecules.

The original version of this Article contained an error in Fig. 1, in which an oxygen atom was missing from the ‘Acetoxonium type’ structure. This has been corrected in both the PDF and HTML versions of the Article.

We present an experimental and theoretical study of the structure of small, neutral gold clusters—Au _3 , Au _4 and Au _7 —‘tagged’ by krypton atoms. Infrared (IR) spectra of Au _N ·Kr _M complexes formed at 100 K are obtained via far-IR multiple photon dissociation in a molecular beam. The theoretical study is based on a statistical (canonical) sampling of the Au _N ·Kr _M complexes through ab initio molecular dynamics using density-functional theory in the generalized gradient approximation, explicitly corrected for long-range van-der-Waals (vdW) interactions. The choice of the functional is validated against higher-level first-principle methods. Thereby finite-temperature theoretical vibrational spectra are obtained that are compared with the experimental spectra. This enables us to identify which structures are present in the experimental molecular beam for a given cluster size. For Au _2 , Au _3 and Au _4 , the predicted vibrational spectra of the Kr-complexed and pristine species differ. For Au _7 , the presence of Kr influences the vibrational spectra only marginally. This behavior is explained in terms of the formation of a weak chemical bond between Kr and small gold clusters that localizes the Kr atom at a defined adsorption site, whereas for bigger clusters the vdW interactions prevail and the Kr adatom is delocalized and orbits the gold cluster. In all cases, at temperatures as low as T = 100 K, vibrational spectra already display a notable anharmonicity and show, in comparison with harmonic spectra, different position of the peaks, different intensities and broadenings, and even the appearance of new peaks.

Large molecules have complex potential-energy surfaces with many local minima. They exhibit multiple stereo-isomers, even at very low temperatures. In this paper we discuss the different approaches for the manipulation of the motion of large and complex molecules, like amino acids or peptides, and the prospects of state- and conformer-selected, focused, and slow beams of such molecules for studying their molecular properties and for fundamental physics studies. [ABSTRACT FROM AUTHOR]

The crossed molecular beam technique has been established as a mature and important experimental method for detailed studies of molecular interactions, and has contributed enormously to our present understanding of molecular reaction dynamics. The Stark deceleration technique yields unprecedented control over both the internal and external degrees of freedom of polar molecules in a molecular beam, offering new possibilities in scattering experiments. In particular, Stark-decelerated molecular beams allow detailed molecular scattering studies as a function of the collision energy, from low to high collision energies, and with a very high energy resolution. We discuss a variety of experimental geometries that exploit this new molecular beam technology for scattering experiments, ranging from crossed beam arrangements and molecular synchrotrons to surface scattering set-ups. [ABSTRACT FROM AUTHOR]

We present the IR spectrum of the gas-phase C60−anion. The C60−anions are mass-selected and trapped in an ion cyclotron mass spectrometer cell. The spectrum is obtained by recording the yield of electrons following infrared multiple photon absorption and subsequent electron detachment of the anions. Two bands are observed that correlate to two of the four IR-allowed transitions in neutral C60. The results show that the higher frequency band is strongly shifted from its position in neutral C60and is a sensitive marker for the charge state. The band positions and intensities are compared to results obtained by theory as well as to known bands in solid samples and good agreement is found. [ABSTRACT FROM AUTHOR]

The vibrational spectra of vanadium oxide anions ranging from V2O6− to V8O20− are studied in the region from 555 to 1670 cm−1 by infrared multiple photon photodissociation (IRMPD) spectroscopy. The cluster structures are assigned and structural trends identified by comparison of the experimental IRMPD spectra with simulated linear IR absorption spectra derived from density functional calculations, aided by energy calculations at higher levels of theory. Overall, the IR absorption of the VmOn− clusters can be grouped in three spectral regions. The transitions of (i) superoxo, (ii) vanadyl and (iii) V–O–V and V–O˙ single bond modes are found at ∼1100 cm−1, 1020 to 870 cm−1, and 950 to 580 cm−1, respectively. A structural transition from open structures, including at least one vanadium atom forming two vanadyl bonds, to caged structures, with only one vanadyl bond per vanadium atom, is observed in-between tri- and tetravanadium oxide anions. Both the closed shell (V2O5)2,3VO3− and open shell (V2O5)2–4− anions prefer cage-like structures. The (V2O5)3,4− anions have symmetry-broken minimum energy structures (Cs) connected by low-energy transition structures of C2v symmetry. These double well potentials for V–O–V modes lead to IR transitions substantially red-shifted from their harmonic values. For the oxygen rich clusters, the IRMPD spectra prove the presence of a superoxo group in V2O7−, but the absence of the expected peroxo group in V4O11−. For V4O11−, use of a genetic algorithm was necessary for finding a non-intuitive energy minimum structure with sufficient agreement between experiment and theory. [ABSTRACT FROM AUTHOR]

The first gas-phase infrared spectra of silicon monoxide cations (SiO)n+, n = 3–5, using multiple photon dissociation in the 550–1250 cm−1 frequency range, are reported. All clusters studied here fragment via loss of a neutral SiO unit. The experimental spectra are compared to simulated linear absorption spectra from calculated low energy isomers for each cluster. This analysis indicates that a “ring” isomer is the primary contributor to the (SiO)3+ spectrum, that the (SiO)4+ spectrum results from two close-lying bicyclic ring isomers, and that the (SiO)5+ spectrum is from a bicyclic ring with a central, fourfold-coordinated Si atom. Experiment and theory indicate that the energies and energetic orderings of (SiO)n+ isomers differ from those for neutral (SiO)n clusters. [ABSTRACT FROM AUTHOR]

We have determined the abundance of two different conformational structures of the mixed benzene dimer (C6H6)(C6D6) in a molecular beam, with various carrier gases. These two T-shaped conformers have a subtle zero-point energy difference of only a few cm−1, and a transition state barrier of about 64 cm−1. Nevertheless, depending on the carrier gas, the lowest energy conformer can exclusively be prepared in the molecular beam. Low-energy two-body collisions of the benzene-dimers with the carrier gas atoms are concluded to be responsible for this. [ABSTRACT FROM AUTHOR]

The magnetic tuning of the low-rotational levels of the A 6Σ (v = 1 and 0) states of chromium monohydride, 52CrH, have been experimentally investigated using optical spectroscopy of the (0, 0) and (1, 0) bands of the A 6Σ–X 6Σ transition. The tuning of the numerous low-rotational lines in the A 6Σ–X 6Σ (0, 0) band can be accurately modeled using a single set of g-factors (gS and g) which are close to the expected values. In contrast, the g-factors for the A 6Σ (v = 1) state required to model the magnetic tuning of low-rotational lines in the A 6Σ–X 6Σ (1, 0) band are strongly dependent upon rotational and fine structure component and the determined effective values for gS deviate significantly from 2.002. Interpretation of the quantum level variation of gS is presented. The magnetic hyperfine structure of the (0, 0) and (1, 0) bands of the A 6Σ–X 6Σ transition is analyzed to produce proton Fermi contact, bF and dipolar, c, magnetic hyperfine parameters of 19(1) MHz and 34(5) MHz for the A 6Σ (v = 0) state and 21(2) MHz and 30(7) MHz for the A 6Σ (v = 1) state. [ABSTRACT FROM AUTHOR]

An H2 molecule can bind molecularly on Ni4+ but it binds exclusively dissociatively on Ni5+ and Ni6+ and the adsorption behavior correlates with the relative reactivity of the metal clusters towards H2. [ABSTRACT FROM AUTHOR]