Search results for "PolyAT"

Ag44(SeR)30: A Hollow Cage Silver Cluster with Selenolate Protection.

2015

Selenolate protected, stable and atomically precise, hollow silver cluster was synthesized using solid state as well as solution state routes. The optical absorption spectrum shows multiple and sharp features similar to the thiolated Ag44 cluster, Ag44(SR)30 whose experimental structure was reported recently. High-resolution electrospray ionization mass spectrometry (HRESI MS) shows well-defined molecular ion features with two, three, and four ions with isotopic resolution, due to Ag44(SePh) 30. Additional characterization with diverse tools confirmed the composition. The closed-shell 18 electron superatom electronic structure, analogous to Ag44(SR)30 stabilizes the dodecahedral cage with a…

On the semi-empirical determination of intramolecular potential energy surface of polyatomic molecule: application to hydrogen sulfide, hydrogen sele…

2007

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.

Multicomponent density-functional theory for time-dependent systems

2007

We derive the basic formalism of density functional theory for time-dependent electron-nuclear systems. The basic variables of this theory are the electron density in body-fixed frame coordinates and the diagonal of the nuclear N-body density matrix. The body-fixed frame transformation is carried out in order to achieve an electron density that reflects the internal symmetry of the system. We discuss the implications of this body-fixed frame transformation and establish a Runge-Gross-type theorem and derive Kohn-Sham equations for the electrons and nuclei. We illustrate the formalism by performing calculations on a one-dimensional diatomic molecule for which the many-body Schrodinger equati…

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.