Advances and Applications of Microwave Spectroscopy (original) (raw)
Related papers
Microwave Spectroscopy of Astrophysical Molecules
Highlights of Astronomy, 1989
Recent detections of new molecules in dense interstellar clouds, first detections of certain chemical elements in interstellar molecules, and new information on isotopic fractionation of hydrogen in the interstellar medium are discussed in the context of the need for new laboratory data on transition rest frequencies, reaction rates, and branching ratios.
Journal of research of the National Institute of Standards and Technology
he developed parallel plate cells coupled with rf and DC discharge methods to study free radicals and transient species. In the mid 1980s Lovas and Suenram constructed a pulsed molecular beam Fourier Transform microwave (FTMW) spectrometer to study hydrogen bonded and van der Waals dimers and trimers. This article describes the types of molecules studied and the type molecular properties derived from these measurements as well as some of the instruments developed for these studies. The two major areas of application described are atmospheric chemistry and molecular radio astronomy.
The microwave spectroscopy study of 1,2-dimethoxyethane
Journal of Molecular Spectroscopy, 2017
The pure rotational spectrum of 1,2-dimethoxyethane was measured in the 6-18 and 59.6-74.4 GHz frequency ranges using a cavity-based pulsed jet Fourier transform microwave spectrometer and a Stark modulated free-jet millimeter-wave absorption spectrometer, respectively. Two conformers, TGT and TGG 0 , have been identified, together with their mono-substituted 13 C isotopologues. Each rotational transition is split into several components due to the two methyl groups internal rotations. The corresponding V 3 barriers have been experimentally determined. MP2/6-311++G(d,p) calculations have provided the determination of the conformational stabilities, structures and spectroscopic parameters.
Microwave Spectroscopy Algorithms for Context-Free Molecular Structure Determination
2020
Microwave Spectroscopy Algorithms for Context-Free Molecular Structure Determination by Lia Yeh Modern microwave spectrometers, including the ones in our lab, can quickly and accurately measure thousands of frequencies which are absorbed by a given molecule. Our goal is to develop a black box methodology to infer molecular structure from these frequencies. The catch is that we aim for a context-free approach; in other words, we know nothing about the molecules we want to analyze except that we can take a microwave spectrum of it. The process of extracting information about the molecules present in our spectra is an inverse problem – you don’t know what you are looking for until you’ve found it. It has been a decades-long goal of the spectroscopy community to procedurally assign even theoretical spectra efficiently. Our algorithm, Robust Automated Assignment of Rigid Rotors (RAARR), is the first to analyze experimental spectra of complex mixtures, successfully assigning rotational co...
The use of the Fabry–Perot interferometer for high resolution microwave spectroscopy
Journal of Molecular Spectroscopy, 2009
A simple Fabry-Perot interferometer was used for measurements of microwave spectra. Both basic experimental arrangements, absorption and emission, were tested on the rotational spectra of acetonitrile. The interferometric results obtained were compared with the spectra measured using a standard high resolution microwave spectrometer.
Microwave spectrum and structure of C6H5CCH⋯H2S complex
Journal of Molecular Spectroscopy, 2011
complexes have been observed using a pulsed nozzle Fourier transform microwave spectrometer. The observed spectrum is consistent with a structure in which hydrogen sulfide is located over the phenyl ring p cloud and the distance between the centers of masses of the two monomers is 3.74 ± 0.01 Å. In the complex, the H 2 S unit is shifted from the phenyl ring center towards the acetylene group. The vibrationally averaged structure has an effective Cs symmetry. Ab initio calculations were performed at MP2/aug-cc-pVDZ level of theory to locate the possible geometries of the complex. The calculations reveal the experimentally observed structure to be more stable than a coplanar arrangement of the monomers, which was observed for the C 6 H 5 CCHÁ Á ÁH 2 O complex. Atoms in molecule theoretical analysis shows the presence of S-HÁ Á Áp hydrogen bond. For the parent isotopologue, each transition frequency was found to split into two resulting from an interchange of the equivalent hydrogens of H 2 S unit in the complex.
Spectroscopic applications of three-level microwave double resonance
Journal of Molecular Structure, 1983
The versatility of a computer controlled double resonance microwave spectrometer has been exploited in three widely differing ways; for quantitative chemical analysis at the percentage level of specific constituents of a gas mixture; for the spectroscopy of forbidden transitions and wideband spectral searches for allowed transitions in torsional states of acetaldehyde; and in the development of techniques for the Fourier transform spectroscopy of both probed and pumped transitions in a three-level system. d'iiF!,her and C Feuillade Chem Phys 26 319-329 (1977) H Bomsdorf and H Dreizler,'Z.Naturforscl!-i6a 473-480 (1981). _'