The predicted spectrum of FeOH in its Renner-degenerate and electronic states (original) (raw)
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The Journal of Physical Chemistry, 1992
A spectroscopic and theoretical study of the electronic structure of Fe(CO)s is reported. The vacuum-UV electronic spectrum of Fe(CO)5 was recorded in the gas phase at room temperature in the region 210-1 10 nm. The spectrum is dominated by a strong absorption with a maximum at 194 nm, followed by a series of strong overlapped bands of increasing intensity. Ab initio CASSCF CCI calculations of the lowest ligand field, the two first ionization energies, and the first s, p, and d terms of the two first Rydberg series were undertaken. The excellent agreement found between experiment and theory for the LF transition and IEs shows the quantitative accuracy of these calculations. The first Rydberg series arises from excitation of one 3d, electron toward 4s, 4p, and 4d atomic-like orbitals and ranges from 49600 to 61 800 an-'. The term value calculated for the 3d,-4s excitation (18 800 cm-I) is close to that deduced from the first Rydberg transition of iron. The second Rydberg series corresponds to excitation of the 3d, levels and falls in the region comprised between 64 100 and 71 800 cm-l. been carried out on the CRAY-2 computer of the CCVR (Palaiseau, France) through a grant of computer time from the Conseil Scientifique du Centre de Calcul Vectoriel pour la Recherche. This work was partially supported by the Direction General de Investigacion Cientifica y T h i c a (grant PB86-0140). Registry No. Fe(CO)5, 13463-40-6. (3 1) Only eight Rydberg transitions are reported in Table 11. Our attempts to converge the CASSCF procedure on the Rydberg state corresponding to the 3d-4d,2 excitation were unsuccessful. Namely the presence of the state corresponding to the 3d-3d,2 in the same symmetry causes the higher root to collapse into the lowest one. (32) Moore, C. E. Afomic Energy levels; Nat. Bur. Stand. Circ. No. 467; US GPO: Washington DC, 1949.
Journal of Chemical Theory and Computation, 2010
A new variational methodology for the treatment of the Renner-Teller effect in tetraatomic molecules has been developed in valence coordinates. The kinetic-energy operator of Bramley et al. [Mol. Phys. 1991, 73, 1183 for any sequentially bonded four-atom molecule, A-B-C-D, in the singlet nondegenerate electronic state has been adapted to the Renner-Teller and spin couplings by modifying the expression of the nuclear angular momentum. The total Schrö dinger equation is solved by diagonalizing the Hamiltonian matrix in a three-step contraction scheme. The main advantage of this new theoretical development is the possibility of studying different isotopomers using the same potential-energy surfaces. This procedure has been tested on HCCH + and its deuterated derivatives DCCD + and DCCH + . The calculated rovibronic band origins were compared with previous data deduced from the Jacobi coordinates methodology, dimensionality reduced variational treatment, and photoelectron spectra with a good global agreement. Rotational structures for these systems are also tackled.
Chemical Physics, 2008
We report the calculation of a six-dimensional CCSD(T)/aug-cc-pVQZ potential energy surface for the electronic ground state of NH þ 3 together with the corresponding CCSD(T)/aug-cc-pVTZ dipole moment and polarizability surface of 14 NH þ 3 . These electronic properties have been computed on a large grid of molecular geometries. A number of newly calculated band centers are presented along with the associated electric-dipole transition moments. We further report the first calculation of vibrational matrix elements of the polarizability tensor components for 14 NH þ 3 ; these matrix elements determine the intensities of Raman transitions. In addition, the rovibrational absorption spectra of the m 2 , m 3 , m 4 , 2m 2 À m 2 , and m 2 þ m 3 À m 2 bands have been simulated.
Ro-vibrational Transition Energies and Absorption Intensities of the< emph type=
Australian Journal of Physics
Variational ro-vibrational wave functions are calculated using an Eckart-Watson Hamiltonian, which has embedded an ab initio potential energy function. These wave functions, together with an ab initio dipole moment function, are employed to predict transition energies and absorption intensities. The radiative transition probability integrals are determined using a novel adaptation of the Harris-Engerholm-Gwinn integration scheme. The method and solution algorithm yields results in excellent agreement with previously determined experimental and theoretical electric dipole allowed transitions for the 1 A 1 ground state of H 2 O. The method has also been applied to the 1 A 1 states of the helide analogs of water, namely He 2 O 2+ and He 2 S 2+ , in order to predict their ro-vibrational transition energies and absorption intensities, thereby facilitating their possible interstellar detection.
Journal of Physics: Conference Series
The quantitative distribution of the molecular abundances in the universe is a classical problem in astronomy, astrophysics and cosmo-chemistry. Astrophysicists are interested in determining the abundances of molecular species in order to: (1) Know the primordial composition of the solar system, and its relation to the past and present composition of the earth. (2) Have a complete understanding of physical and chemical processes taking place in the stellar atmospheres and the interstellar medium (3) Test the hypotheses that have been proposed for element formation. To investigate the presence of astronomical sources, experimental astrophysicists usually study the wavelength and intensity of light that they emit. Many diatomic molecular species are present in various astrophysical sources, however, the theoretical studies on such species are not enough and information is missing in that area. Knowledge of the electronic structure, Franck-Condon factors (FCFs), and other related quantities for a band system of a diatomic molecule is essential to arrive at its astrophysically significant parameters such as kinetics of the energy transfer, radiative lifetimes, band intensity, vibrational temperature, etc. In this view, the spectroscopic and ro-vibrational constants, FCFs of several electronic states of the diatomic molecule SiS electronic have been evaluated in this work. We performed theoretical calculation of the low-lying electronic state, of the molecule SiS by using the Complete Active Space Self Consistent Field (CASSCF) method followed by the Multi Reference Configuration Interaction with Davidson correction MRCI+Q. The potential energy along with the dipole moment curves of these states have been calculated along with the spectroscopic constants Re, e, Be, and Te. Additionally, the Rotation-vibration lines for the considered electronic states were obtained by direct solution of the nuclear motion Schrödinger equation using the canonical approach with program Rovib-1
Atomic Structure Variational Calculations in Spectroscopy
Physica Scripta, 1998
Recent ab initio variational calculations of radiative transition probabilities, isotope shifts and hyperÐne structures are described in the spirit of the EGAS tradition for plenary talks. A few simple cases are selected to make the expose at a level accessible to non-specialists in the Ðeld and to illustrate how computational atomic structure can be used in atomic spectroscopy for testing theoretical models or experimental results, predicting properties or interpreting them in terms of electron correlation. The e †ects inherent in the multiconÐguration HartreeÈFock method due to its variational nature are emphasized through some simple analysis of the wave function spatial distribution in correlation with the model used.