Search results for "ORBIT"
showing 10 items of 1104 documents
Ground state and electronic spectrum of Cu(ii) and Cu(iii) complexes of N,N′-1,2-phenylenebis-2-mercaptoacetamide
2009
The electronic structure and the UV-vis spectrum of reduced and oxidized model systems of the N,N'-1,2-phenylenebis(2-mercapto-2-methylpropionamide) copper complex have been studied using a multiconfigurational quantum chemical method (CASSCF/CASPT2). The bonds between Cu and the two sulfur ligand atoms have a large covalent character in the oxidized Cu(III) form. As a result of the increased covalency, the effective charge on the Cu atom is actually smaller in the oxidized form. The electronic spectrum for both oxidation states of the complex is in agreement with the experiment for excitation energies and intensities showing that the theoretical description of the electronic structure is e…
ChemInform Abstract: Comparative G2(MP2) Molecular Orbital Study of B3H7XH3 and H3BXH3 Donor-Acceptor Complexes (X: N, P, and As).
2010
B3H7XH3 and H3BXH3 (X = N, P, and As) have been studied as donor−acceptor complex type at the G2(MP2) level of theory. Both single- and double-bridged structures of B3H7 Lewis acid are taken into account. Although the double-bridged structure is energetically favored in the isolated state, the coordination prefers the single-bridged one. The monoborane adducts adopt the staggered arrangement with C3v symmetry. The energetic analysis by natural bond orbital theory shows that the decrease of hyperconjugative contribution upon complexation in the B3H7 moiety has, as consequence, a loss of symmetry for B3H7XH3 (X= P and As) complexes. In the two series, the coordination is the result of two opp…
Ab initiosimulations on rutile-based titania nanowires
2012
The rod symmetry groups for monoperiodic (1D) nanostructures have been applied for construction of models for bulk-like TiO2 nanowires (NWs) cut from a rutile-based 3D crystal along the chosen [001] and [110] directions of crystallographic axes. In this study, we have considered nanowires described by both the Ti-atom centered rotation axes as well as the hollow site centered axes passing through the interstitial positions between the Ti and O atoms closest to the axes. The most stable [001]-oriented TiO2 NWs with rhombic cross sections are found to display the energetically preferable {110} facets only while the nanowires with quasi-square sections across the [110] axis are formed by the a…
Spin Transitions in Iron(II) Complexes
1996
Iron(II) has the 3d6 outer electronic configuration and hence its octahedral complexes may be either high-spin or low-spin. The high-spin configuration, t 2g 4 e g 2 , is adopted when relatively weak-field ligands are coordinated while the low-spin, t 2g 6 e g 0 , is obtained when strong-field ligands are involved. In Oh symmetry the ground states are 5T2g and lA1g, for the high-spin and low-spin configurations, respectively. While in most iron(II) six-coordinate complexes the symmetry is lower than Oh, these designations are generally adopted in the following sections for convenience. [Fe(H2O)6]2+ and [Fe(en)3]2+ (en = ethylenediamine) are typical examples of high-spin complexes, while [Fe…
Bifurcations of cuspidal loops
1997
A cuspidal loop for a planar vector field X consists of a homoclinic orbit through a singular point p, at which X has a nilpotent cusp. This is the simplest non-elementary singular cycle (or graphic) in the sense that its singularities are not elementary (i.e. hyperbolic or semihyperbolic). Cuspidal loops appear persistently in three-parameter families of planar vector fields. The bifurcation diagrams of unfoldings of cuspidal loops are studied here under mild genericity hypotheses: the singular point p is of Bogdanov - Takens type and the derivative of the first return map along the orbit is different from 1. An analytic and geometric method based on the blowing up for unfoldings is propos…
Light-controlled reversible modulation of frontier molecular orbital energy levels in trifluoromethylated diarylethenes
2017
Among bistable photochromic molecules, diarylethenes (DAEs) possess the distinct feature that upon photoisomerization they undergo a large modulation of their π-electronic system, accompanied by a marked shift of the HOMO/LUMO energies and hence oxidation/reduction potentials. The electronic modulation can be utilized to remote-control charge- as well as energy-transfer processes and it can be transduced to functional entities adjacent to the DAE core, thereby regulating their properties. In order to exploit such photoswitchable systems it is important to precisely adjust the absolute position of their HOMO and LUMO levels and to maximize the extent of the photoinduced shifts of these energ…
Theoretical Determination of the Singlet → Singlet and Singlet → Triplet Electronic Spectra, Lowest Ionization Potentials, and Electron Affinity of C…
2003
The singlet → singlet and singlet → triplet electronic spectra of cycloocta-1,3,5,7-tetraene are studied using multiconfigurational second-order perturbation theory (CASPT2) and extended atomic natural orbitals (ANOs) basis sets. The observed dipole-allowed features at 4.43, 6.02, and 6.42 eV and the spin-forbidden singlet → triplet bands with maxima at 3.05, 4.05, and 4.84 eV (Frueholz, R. P.; Kuppermann, A. J. Chem. Phys. 1978, 69, 3614) are assigned as the transitions 1 1 A 1 → 1 1 A 2 , 1 1 A 1 → 2 1 B 2 (3p z ), 1 1 A 1 → 3 1 E, and 1 1 A 1 - 1 3 A 2 , 1 1 A 1 → 1 3 E, 1 1 A 1 → 1 3 B 1 , respectively. The lowest (3s) Rydberg singlet and triplet states are placed at 5.58 (2 1 A 1 ) and…
FRIPON: a worldwide network to track incoming meteoroids
2020
Context. Until recently, camera networks designed for monitoring fireballs worldwide were not fully automated, implying that in case of a meteorite fall, the recovery campaign was rarely immediate. This was an important limiting factor as the most fragile - hence precious - meteorites must be recovered rapidly to avoid their alteration. Aims. The Fireball Recovery and InterPlanetary Observation Network (FRIPON) scientific project was designed to overcome this limitation. This network comprises a fully automated camera and radio network deployed over a significant fraction of western Europe and a small fraction of Canada. As of today, it consists of 150 cameras and 25 European radio receiver…
Direct Peel Monitoring of Xenobiotics in Fruit by Direct Analysis in Real Time Coupled to a Linear Quadrupole Ion Trap–Orbitrap Mass Spectrometer
2013
Study of xenobiotics present in fruit peel by exposing it (without any pretreatment) to direct analysis in real time coupled to a high-resolution orbitrap mass spectrometer (DART-HRMS) is reported for the first time. Variables such as DART gas heater temperature and pressure, source-to-MS distance, and sample velocity are investigated. The analysis of one sample by DART-MS lasts ca. 1 min, and the benefits of both high-resolution and tandem mass spectrometry to elucidate nontarget or unknown compounds are combined. Identification of postharvest fungicides, antioxidants, and sugars in fruit peel is performed in the positive ion mode. A possible elemental formula is suggested for marker compo…
Climate Data Records of Vegetation Variables from Geostationary SEVIRI/MSG Data: Products, Algorithms and Applications
2019
The scientific community requires long-term data records with well-characterized uncertainty and suitable for modeling terrestrial ecosystems and energy cycles at regional and global scales. This paper presents the methodology currently developed in EUMETSAT within its Satellite Application Facility for Land Surface Analysis (LSA SAF) to generate biophysical variables from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on board MSG 1-4 (Meteosat 8-11) geostationary satellites. Using this methodology, the LSA SAF generates and disseminates at a time a suite of vegetation products, such as the leaf area index (LAI), the fraction of the photosynthetically active radiation absorbed …