The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Yasuki Endo - One of the best experts on this subject based on the ideXlab platform.
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fourier transform Microwave Spectroscopy of dimethyl substituted criegee intermediate ch3 2coo
Journal of Chemical Physics, 2016Co-Authors: Masakazu Nakajima, Yasuki EndoAbstract:Pure rotational transitions of the dimethyl-substituted Criegee intermediate (dimethyl carbonyl oxide, acetone oxide), (CH3)2COO, were observed in the discharge plasma of a C(CH3)2I2/O2 gas mixture by Fourier-transform Microwave Spectroscopy. The observed spectra show small splittings due to the internal rotations of the two methyl groups. Precise rotational constants of the molecule and the barrier heights of the methyl internal rotations were experimentally determined.
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fourier transform Microwave Spectroscopy of an alkyl substituted criegee intermediate anti ch3choo
Journal of Molecular Spectroscopy, 2015Co-Authors: Masakazu Nakajima, Yasuki EndoAbstract:Abstract Pure rotational transitions of the anti-form of the simplest alkyl-substituted Criegee intermediate, anti-CH3CHOO, were observed by Fourier-transform Microwave Spectroscopy. The observed transition frequencies in the A and E levels of the ground vibrational state were analyzed together, and molecular constants including parameters which characterize the internal rotation of the methyl rotor were determined. The experimentally determined barrier height of the three-fold potential for the methyl internal rotation is 399.1 cm−1, less than a half of that of the other conformer, syn-CH3CHOO (Nakajima and Endo, 2014).
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Laboratory detections of SiC2N and SiC3N by Fourier transform Microwave Spectroscopy
Journal of Chemical Physics, 2014Co-Authors: Hiroya Umeki, Masakazu Nakajima, Yasuki EndoAbstract:Two silicon-bearing carbon chain radicals, SiC2N and SiC3N, were detected in the laboratory by Fourier transform Microwave Spectroscopy. Molecular constants including the hyperfine coupling constants have been determined for the two radicals in the ground electronic states. The SiC2N and SiC3N radicals have linear structures in the 2Π ground electronic states with inverted and regular fine structures, respectively, as are the cases for their isoelectronic radicals, SiC3H and SiC4H, indicating that the SiCnN radicals have similar electronic structures to the SiCn+1H radicals. The electronic structures of SiC2N and SiC3N in the ground states are discussed on the basis of the experimentally determined molecular constants.
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Fourier-transform Microwave Spectroscopy of the vinoxy radical, CH2CHO
Journal of Molecular Spectroscopy, 2014Co-Authors: Yasuki Endo, Masakazu NakajimaAbstract:Abstract Pure rotational transitions of the vinoxy radical in the ground vibronic state have been observed by Fourier-transform Microwave Spectroscopy in the cm-wave region and double resonance Spectroscopy in the mm-wave region. Total of 6 rotational transitions are newly observed in the present work, which are least squares fitted together with the mm-wave data observed previously (Endo et al., 1985). The hyperfine coupling constants for the third proton in the –CHO moiety of the vinoxy radical have been determined precisely for the first time. Four b -type transitions, that escaped to be detected in the previous study in the mm-wave region, have provided a more accurate set of molecular constants for the ground vibronic state.
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Fourier-transform Microwave Spectroscopy of the H2-HCN complex
Chemical Physics Letters, 2012Co-Authors: M. Ishiguro, Yoshihiro Sumiyoshi, Kensuke Harada, Keiichi Tanaka, Takehiko Tanaka, Yasuki EndoAbstract:Fourier-transform Microwave Spectroscopy was applied to observe the J = 1–0 rotational transition of the H2–HCN complex for both the ortho- and para-H2 species to obtain improved molecular constants by an analysis combined with the millimeter-wave data. It was confirmed that the para- and ortho-H2 species have different configurations: namely H2 is attached to the H end of HCN in the former, while to the N end in the latter. For the ortho-H2 species, the hyperfine splitting due to the magnetic interaction between the hydrogen nuclei was observed to give the nuclear spin–spin coupling constant dH = 54.6(38) kHz.
John M Doyle - One of the best experts on this subject based on the ideXlab platform.
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identifying enantiomers in mixtures of chiral molecules with broadband Microwave Spectroscopy
Angewandte Chemie, 2014Co-Authors: Alvin V Shubert, David Patterson, John M Doyle, David Schmitz, Melanie SchnellAbstract:Chirality-sensitive broadband Microwave Spectroscopy was performed on mixtures of carvone enantiomers and conformers to distinguish enantiomers, measure enantiomeric excesses, and determine the absolute configurations of the enantiomers. This method uses Microwave three-wave mixing and is inherently well-suited to the analysis of mixtures—a unique advantage over other techniques. In contrast to conventional Microwave Spectroscopy, the phase of the received signal is also exploited. This phase depends upon the signs of the molecules’ dipole-moment components and is used to identify the excess enantiomer. The measured signal amplitude determines the size of the excess. The broadband capabilities of the spectrometer were used to simultaneously excite and measure two conformers of carvone, demonstrating the analysis of a sample with multiple chiral species. Employing quantum chemical calculations and the measured phases, the absolute configurations of the enantiomers are determined.
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enantiomer specific detection of chiral molecules via Microwave Spectroscopy
Nature, 2013Co-Authors: David Patterson, Melanie Schnell, John M DoyleAbstract:Microwave Spectroscopy is used to map the sign of an electric dipole Rabi frequency — which depends directly on the chirality of the molecule — onto the phase of emitted Microwave radiation, thereby determining the chirality of cold gas-phase molecules.
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enantiomer specific detection of chiral molecules via Microwave Spectroscopy
Nature, 2013Co-Authors: David Patterson, Melanie Schnell, John M DoyleAbstract:Microwave Spectroscopy is used to map the sign of an electric dipole Rabi frequency — which depends directly on the chirality of the molecule — onto the phase of emitted Microwave radiation, thereby determining the chirality of cold gas-phase molecules. Chiral molecules exist as enantiomers that form non-superimposable mirror images, and chirality has a fundamental role in many aspects of chemistry and biology. It is notoriously difficult to detect and quantify chirality because conventional spectroscopic methods exploit weak effects that produce weak signals. Patterson et al. now show that Microwave Spectroscopy combined with a switched electric field can map the sign of an electric dipole Rabi frequency — a variable that depends directly on the chirality of the molecule — onto the phase of emitted Microwave radiation. The effect is then used to determine the chirality of cold gas-phase molecules, illustrated with S and R enantiomers of 1,2-propanediol and their racemic mixture. The method produces large and definitive signatures of chirality, and is both sensitive and species-selective — making it a potentially ideal and unique tool for determining the chirality of multiple species in a mixture. Chirality plays a fundamental part in the activity of biological molecules and broad classes of chemical reactions, but detecting and quantifying it remains challenging1. The spectroscopic methods of choice are usually circular dichroism and vibrational circular dichroism, methods that are forbidden in the electric dipole approximation2. The resultant weak effects produce weak signals, and thus require high sample densities. In contrast, nonlinear techniques probing electric-dipole-allowed effects have been used for sensitive chiral analyses of liquid samples3,4,5,6,7. Here we extend this class of approaches by carrying out nonlinear resonant phase-sensitive Microwave Spectroscopy of gas phase samples in the presence of an adiabatically switched non-resonant orthogonal electric field; we use this technique to map the enantiomer-dependent sign of an electric dipole Rabi frequency onto the phase of emitted Microwave radiation. We outline theoretically how this results in a sensitive and species-selective method for determining the chirality of cold gas-phase molecules, and implement it experimentally to distinguish between the S and R enantiomers of 1,2-propanediol and their racemic mixture. This technique produces a large and definitive signature of chirality, and has the potential to determine the chirality of multiple species in a mixture.
Melanie Schnell - One of the best experts on this subject based on the ideXlab platform.
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structure determination of trans cinnamaldehyde by broadband Microwave Spectroscopy
Physical Chemistry Chemical Physics, 2015Co-Authors: Sabrina Zinn, Thomas Betz, Chris Medcraft, Melanie SchnellAbstract:The rotational spectrum of trans-cinnamaldehyde ((E)-3-phenyl-2-propenal, C9H8O) was recorded by chirped-pulse Fourier transform Microwave Spectroscopy in the frequency range of 2–8.5 GHz. The odourant molecule is the essential component of cinnamon oil and causes the characteristic smell. The rotational signatures of two conformers were observed: s-trans–trans- and s-cis–trans-cinnamaldehyde. The rotational spectra of s-trans–trans-cinnamaldehyde and all of its 13C-monosubstituted species in natural abundance were assigned and the corresponding carbon backbone structure was determined. The second conformer s-cis–trans-cinnamaldehyde is about 9 kJ mol−1 higher in energy and could also be identified in the spectrum.
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identifying enantiomers in mixtures of chiral molecules with broadband Microwave Spectroscopy
Angewandte Chemie, 2014Co-Authors: Alvin V Shubert, David Patterson, John M Doyle, David Schmitz, Melanie SchnellAbstract:Chirality-sensitive broadband Microwave Spectroscopy was performed on mixtures of carvone enantiomers and conformers to distinguish enantiomers, measure enantiomeric excesses, and determine the absolute configurations of the enantiomers. This method uses Microwave three-wave mixing and is inherently well-suited to the analysis of mixtures—a unique advantage over other techniques. In contrast to conventional Microwave Spectroscopy, the phase of the received signal is also exploited. This phase depends upon the signs of the molecules’ dipole-moment components and is used to identify the excess enantiomer. The measured signal amplitude determines the size of the excess. The broadband capabilities of the spectrometer were used to simultaneously excite and measure two conformers of carvone, demonstrating the analysis of a sample with multiple chiral species. Employing quantum chemical calculations and the measured phases, the absolute configurations of the enantiomers are determined.
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enantiomer specific detection of chiral molecules via Microwave Spectroscopy
Nature, 2013Co-Authors: David Patterson, Melanie Schnell, John M DoyleAbstract:Microwave Spectroscopy is used to map the sign of an electric dipole Rabi frequency — which depends directly on the chirality of the molecule — onto the phase of emitted Microwave radiation, thereby determining the chirality of cold gas-phase molecules.
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enantiomer specific detection of chiral molecules via Microwave Spectroscopy
Nature, 2013Co-Authors: David Patterson, Melanie Schnell, John M DoyleAbstract:Microwave Spectroscopy is used to map the sign of an electric dipole Rabi frequency — which depends directly on the chirality of the molecule — onto the phase of emitted Microwave radiation, thereby determining the chirality of cold gas-phase molecules. Chiral molecules exist as enantiomers that form non-superimposable mirror images, and chirality has a fundamental role in many aspects of chemistry and biology. It is notoriously difficult to detect and quantify chirality because conventional spectroscopic methods exploit weak effects that produce weak signals. Patterson et al. now show that Microwave Spectroscopy combined with a switched electric field can map the sign of an electric dipole Rabi frequency — a variable that depends directly on the chirality of the molecule — onto the phase of emitted Microwave radiation. The effect is then used to determine the chirality of cold gas-phase molecules, illustrated with S and R enantiomers of 1,2-propanediol and their racemic mixture. The method produces large and definitive signatures of chirality, and is both sensitive and species-selective — making it a potentially ideal and unique tool for determining the chirality of multiple species in a mixture. Chirality plays a fundamental part in the activity of biological molecules and broad classes of chemical reactions, but detecting and quantifying it remains challenging1. The spectroscopic methods of choice are usually circular dichroism and vibrational circular dichroism, methods that are forbidden in the electric dipole approximation2. The resultant weak effects produce weak signals, and thus require high sample densities. In contrast, nonlinear techniques probing electric-dipole-allowed effects have been used for sensitive chiral analyses of liquid samples3,4,5,6,7. Here we extend this class of approaches by carrying out nonlinear resonant phase-sensitive Microwave Spectroscopy of gas phase samples in the presence of an adiabatically switched non-resonant orthogonal electric field; we use this technique to map the enantiomer-dependent sign of an electric dipole Rabi frequency onto the phase of emitted Microwave radiation. We outline theoretically how this results in a sensitive and species-selective method for determining the chirality of cold gas-phase molecules, and implement it experimentally to distinguish between the S and R enantiomers of 1,2-propanediol and their racemic mixture. This technique produces a large and definitive signature of chirality, and has the potential to determine the chirality of multiple species in a mixture.
P Thaddeus - One of the best experts on this subject based on the ideXlab platform.
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isofulminic acid honc ab initio theory and Microwave Spectroscopy
Journal of Chemical Physics, 2009Co-Authors: M Mladenovic, Michael C Mccarthy, Marius Lewerenz, P ThaddeusAbstract:Isofulminic acid, HONC, the most energetic stable isomer of isocyanic acid HNCO, higher in energy by 84 kcal/mol, has been detected spectroscopically by rotational Spectroscopy supported by coupled cluster electronic structure calculations. The fundamental rotational transitions of the normal, carbon-13, oxygen-18, and deuterium isotopic species have been detected in the centimeter band in a molecular beam by Fourier transform Microwave Spectroscopy, and rotational constants and nitrogen and deuterium quadrupole coupling constants have been derived. The measured constants agree well with those predicted by ab initio calculations. A number of other electronic and spectroscopic parameters of isofulminic acid, including the dipole moment, vibrational frequencies, infrared intensities, and centrifugal distortion constants have been calculated at a high level of theory. Isofulminic acid is a good candidate for astronomical detection with radio telescopes because it is highly polar and its more stable isomers (HNCO, HOCN, and HCNO) have all been identified in space.
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high resolution Microwave Spectroscopy of the isomeric pair vinylcyanoacetylene and cyanovinylacetylene
Journal of Molecular Spectroscopy, 2004Co-Authors: S Thorwirth, Michael C Mccarthy, John Dudek, P ThaddeusAbstract:The carbon chain molecules vinylcyanoacetylene and cyanovinylacetylene have been investigated between 8 and 41 GHz by Fourier transform Microwave Spectroscopy of a supersonic molecular beam. Owing to the high spectral resolution of the present technique, significantly more accurate rotational and centrifugal distortion constants have been derived for both molecules. In addition, the dipole moments have been calculated at the B3LYP/cc-pVTZ level of theory. Because these carbon chains are similar in structure and composition to known astronomical molecules and because of their high polarity, both species are good candidates for radioastronomical detection.
Peter Krogstrup - One of the best experts on this subject based on the ideXlab platform.
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spin orbit splitting of andreev states revealed by Microwave Spectroscopy
Physical Review X, 2019Co-Authors: L Tosi, Jesper Nygard, C Metzger, M F Goffman, C Urbina, H Pothier, Sunghun Park, Levy A Yeyati, Peter KrogstrupAbstract:We have performed Microwave Spectroscopy of Andreev states in superconducting weak links tailored in an InAs-Al (core-full shell) epitaxially-grown nanowire. The spectra present distinctive features, with bundles of four lines crossing when the superconducting phase difference across the weak link is 0 or $\pi.$ We interpret these as arising from zero-field spin-split Andreev states. A simple analytical model, which takes into account the Rashba spin-orbit interaction in a nanowire containing several transverse subbands, explains these features and their evolution with magnetic field. Our results show that the spin degree of freedom is addressable in Josephson junctions, and constitute a first step towards its manipulation.
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Microwave Spectroscopy of spinful andreev bound states in ballistic semiconductor josephson junctions
Nature Physics, 2017Co-Authors: David Van Woerkom, Alex Proutski, Bernard Van Heck, Daniel Bouman, Jukka I Vayrynen, L I Glazman, Peter Krogstrup, Jesper Nygard, L P Kouwenhoven, Attila GeresdiAbstract:The superconducting proximity effect in semiconductor nanowires has recently enabled the study of new superconducting architectures, such as gate-tunable superconducting qubits and multiterminal Josephson junctions. As opposed to their metallic counterparts, the electron density in semiconductor nanosystems is tunable by external electrostatic gates, providing a highly scalable and in situ variation of the device properties. In addition, semiconductors with large g-factor and spin–orbit coupling have been shown to give rise to exotic phenomena in superconductivity, such as φ0 Josephson junctions and the emergence of Majorana bound states. Here, we report Microwave Spectroscopy measurements that directly reveal the presence of Andreev bound states (ABS) in ballistic semiconductor channels. We show that the measured ABS spectra are the result of transport channels with gate-tunable, high transmission probabilities up to 0.9, which is required for gate-tunable Andreev qubits and beneficial for braiding schemes of Majorana states. For the first time, we detect excitations of a spin-split pair of ABS and observe symmetry-broken ABS, a direct consequence of the spin–orbit coupling in the semiconductor. Andreev bound states in semiconductor–superconductor hybrid structures are studied using Microwave Spectroscopy — a tool that could be also used for investigating Majorana modes.