Search results for "Polyatomic ion"
showing 10 items of 47 documents
Gas chromatography/mass spectrometry of catechol estrogens
1992
Abstract Catecholestrogens (CCEs), namely 2- or 4-hydroxyestradiol and hydroxyestrone, are highly polar, reactive, and extremely labile estrogen metabolites in many experimental conditions. For these reasons, indirect assay methods mainly have been used. Some experimental evidence suggests that CCEs are synthesized and biologically active mostly in target cells. At this level, unfortunately, the indirect assays cannot be used. We present a method of gas Chromatographic/mass spectral (GC/MS) analysis for the identification of individual CCEs; the major fragmentation ions of authentic estrogen standards as trimethylsilylether derivatives, and the MS patterns of the major CCEs, namely, 2-hydro…
New approaches to stored cluster ions
2003
Ion traps are “wall-less containers” which allow the extended storage of selected species. During the storage various interaction steps may be repeatedly applied. To this end no further hardware has to be added - in contrast to beam experiments. In this progress report two examples of recent developments are presented: the experiments have been performed with metal clusters stored in a Penning (ion cyclotron resonance) trap. A new experimental scheme has been developed which allows precision measurements of the dissociation energies of polyatomic species. It has been triggered by investigations on the delayed photodissociation of stored metal clusters. However, the technique is also readily…
Gas-Phase Spectroscopic Detection and Structural Elucidation of Carbon-Rich Group 14 Binary Clusters: Linear GeC3Ge
2016
Guided by high-level quantum-chemical calculations at the CCSD(T) level of theory, the first polyatomic germanium-carbon cluster, linear Ge2C3, has been observed at high spectral resolution in the gas phase through its remarkably complex fundamental antisymmetric C-C stretching mode ν3 located at 1932 cm(-1). The observation of a total of six isotopic species permits the derivation of a highly accurate value for the equilibrium Ge-C bond length. The present study suggests that many more Ge-C species might be detectable in the future using a combination of laser-ablation techniques for production and high-resolution infrared and/or microwave techniques for spectroscopic detection.
Algebraic approach to vibrational spectra of tetrahedral molecules. First order infrared intensity model.
1995
International audience; The algebraic approach we have proposed to describe the vibrational stretching modes of polyatomic molecules (Leroy and Michelot, J. Mol. Spectrosc. 151, 71–96 (1992); Can. J. Phys. 72, 274–289 (1994)) is applied to the silane molecule for up to seven quanta. We then suggest a form of the dipole operator adapted to the (n000) local states by combining the strength of group theory method with the necessity of a compact formulation.
The High Resolution Infrared Spectrum of CH3D in the Region 900–1700 cm−1
1997
The high resolution absorption spectrum of CH(sub 3)D in the region of 900-1700 cm(sup -1) has been revisited on the basis of new long path experimental data recorded with the Fourier transform spectrometer at Kitt Peak. A theoretical model used previously for spherical rotors has been adapted for polyatomic molecules in order to analyze the vibrational polyads of CH(sub 3)D simultaneously.
Improved Algorithms for the Modeling of Vibrational Polyads of Polyatomic Molecules: Application toT,O, andC3Molecules
1997
Abstract Improved algorithms for the construction of rovibrational operators of polyatomic molecules are presented. Vibrationally diagonal and off-diagonal terms are obtained by a specific coupling scheme of creation and annihilation elementary operators. Recursive procedures are used to generate all possible terms and associated basis functions as well as to calculate matrix elements and commutators. Explicit formulations are given forTd,Oh, andC3vmolecules.
Model-free determination of dissociation energies of polyatomic systems.
2001
We describe and apply a new procedure that allows a direct determination of dissociation energies of polyatomic systems (clusters, fullerenes, polymers, and other molecules) without any modeling of the systems under investigation. As an example, we have determined the dissociation energies of a series of gold clusters Au(+)n. A comparison with values obtained from statistical models of unimolecular dissociation shows that these models significantly fail to describe the data. In contrast, the new method yields values which are an order of magnitude more accurate, thus allowing one to experimentally set benchmarks for any theory which attempts to describe activated processes.
Rotational Transitions of CO+Induced by Atomic Hydrogen
2008
The CO+ molecular ion has been observed in photon-dominated regions. Recent modeling has not been able to explain the abundances of CO+ in these regions. The most abundant collision partners are believed to be hydrogen atoms, hydrogen molecules, and electrons. The reactions of these species with CO+ have been studied previously and found to be fast. The only inelastic processes studied before were collisions of CO+ with electrons. Here we investigate the inelastic collisions of CO+ with hydrogen atoms. We argue that this can be done on the lowest triplet electronic state. This implies that CO+ ions, in a hydrogen atom dominated surrounding, experiences a few inelastic collisions before reac…
Electron and nuclear dynamics of a molecular ion in an intense laser field
2004
The dynamics of a two-dimensional $\mathrm{H}_{2}^{+}$ molecule interacting with a strong laser pulse beyond the usual approximation of fixed nuclei is presented. The motion of the nuclei is studied by using the classical Newton laws while the electron is described with a full quantal treatment. The axis of the molecule, initially not aligned to the laser field, performs a long-period pendular motion around the laser polarization axis. Vibrational degrees of freedom are seen to be excited. The radiation emitted by the oscillating charges presents variations that are synchronous to the pendular motion. The possibility of monitoring the motion of the molecule through the emitted radiation is …
β-decay of22O
2005
A mass-separated 12 C 22 O molecular ion beam from the ISOLDE facility was used to study the decay of neutron-rich 22 O. The experimental results were compared with the results from an earlier experiment and predictions by shellmodel calculations using various effective interactions. The mechanism leading to the vanishing decay strength to the first 1 + level of the 22 F nucleus, predicted with the USD effective interaction but not supported by the experimental data, is analysed.