Configuration localized Morse wave functions: Application to vibrational transitions in anharmonic diatomic molecules

The bound states of a Morse potential are described in terms of a basis of states that are characterized for being eigenstates of the Morse variable. These states are strongly localized in configuration space; thus they are called configuration localized Morse (CLM) wave functions. These are shown to provide a powerful tool to calculate analytically, to a good approximation, matrix elements of arbitrary functions of the interatomic separation between vibrational states of anharmonic diatomic molecules. Applications of CLM wave functions to the calculation of vibrational transitions in HF and DF diatomic molecules are presented.Dirección General de Investigación Científica y Técnica PB95-0533European Commission CI1*-CT94-007

An Approach to Global Rovibrational Analysis Based on Anharmonic Ladder Operators: Application to Hydrogen Selenide (H80 2 Se)

An algebraic approach to perform global rovibrational analysis of molecular spectra is presented. The approach combines the onedimensional limit of the vibron model with rotational degrees of freedom. The model is based on the expression of the phase space Hamiltonian in terms of anharmonic ladder operators and the use of a symmetry-adapted basis set given by the linear combination of products of local vibrational and rotational wavefunctions. As an example we model the rovibrational spectra of a bent triatomic molecule, providing a global analysis for vibrational bands up to polyad 12 and Jmax=5 of Hydrogen Selenide (H2Se). Satisfactory fits of vibrational and rovibrational energies are obtained. A prediction of 2579 rovibrational energies up to J ≤ 5 and polyad 12 for the 140 lowest vibrational bands is also obtained. A possible extension of the model to reach spectroscopic quality results in larger molecular systems is also given

Analytic evaluation of Franck-Condon integrals for anharmonic vibrational wave functions

The problem of calculating Franck-Condon overlap integrals in molecular transitions between vibrational states in different electronic configurations is addressed. An exact and easily applicable analytical expression is obtained when the vibrational states can be approximated by eigenstates of Morse potentials with different strengths and locations but identical ranges. An approximate analytical expression is obtained for the general case. The method is applied to the stretching S-S mode corresponding to [Formula Presented] transitions in the [Formula Presented] molecule.Dirección General de Investigación Científica y Técnica PB95-053

Excited state quantum phase transitions in the bending spectra of molecules

European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 87208

Global assignment and extension of millimeter- and submillimeter-wave spectral database of 13C1-methyl formate (H13COOCH3) in the ground and first excited states

A compilation of the available spectroscopic millimeter- and submillimeter-wave data of the ground and first excited states of C-13(1)-methyl formate ((HCOOCH3)-C-13) has been carried out. The exhaustive analysis of the available transition lines of (HCOOCH3)-C-13 has led to the assignment of 7457 spectral lines by means of a global fit of 45 parameters, using the Rho-Axis Method and the BELGI-Cs code, with a resulting unitless standard deviation of 0.57. Over 1600 lines are included for the first time in the fit. In addition, the line strengths of spectral lines are also calculated using the most recent experimental measurement of the electric dipole moment. In conclusion, the present study represents a notable improvement with respect to previous (HCOOCH3)-C-13 spectral analyses. Therefore, the better accuracy of the present analysis may help the future identification of new (HCOOCH3)-C-13 lines in the interstellar and circumstellar media, and may contribute to decrease some of the spectral confusion due to these species in astronomical surveys

Configuration localized wave functions: General formalism and applications to vibrational spectroscopy of diatomic molecules

A general formalism for constructing configuration localized states for one-dimensional potentials is presented. It allows the evaluation of accurate approximations to the vibrational matrix elements of the momentum operator and of arbitrary functions of the coordinate. The formalism is applied to three potentials of interest in molecular physics: the harmonic oscillator, Morse, and Pöschl-Teller potentials. Quadratures specifically designed for each potential are used. The infrared vibrational spectrum of [Formula Presented] is studied as a way to test the results obtained for different potentials in connection with their ability to model the anharmonicity

Highly correlated ab initio study of the far infrared spectra of methyl acetate

Highly correlated ab initio calculations (CCSD(T)) are used to compute gas phase spectroscopic parameters of three isotopologues of the methyl acetate (CH3COOCH3, CD3COOCH3, and CH3COOCD3), searching to help experimental assignments and astrophysical detections. The molecule shows two conformers cis and trans separated by a barrier of 4457 cm−1. The potential energy surface presents 18 minima that intertransform through three internal rotation motions. To analyze the far infrared spectrum at low temperatures, a three-dimensional Hamiltonian is solved variationally. The two methyl torsion barriers are calculated to be 99.2 cm−1 (C–CH3) and 413.1 cm−1 (O–CH3), for the cis-conformer. The three fundamental torsional band centers of CH3COOCH3 are predicted to lie at 63.7 cm−1 (C–CH3), 136.1 cm−1 (O–CH3), and 175.8 cm−1 (C–O torsion) providing torsional state separations. For the 27 vibrational modes, anharmonic fundamentals and rovibrational parameters are provided. Computed parameters are compared with those fitted using experimental data

THz extended spectrum of the monodeuterated methyl formate (DCOOCH3)

Context. Laboratory spectral recordings and an accurate molecular spectral analysis of any potential interstellar molecule are essential for generating a complete spectroscopic line list. This permits predicting the frequencies and intensities of any transition so that subsequently, it can be identified in the interstellar medium. Aims. Our analysis of DCOOCH3 aims to provide a comprehensive spectral catalog that encompasses as much as possible the frequency coverage of the new-generation far-IR and submillimeter wave observation facilities. Methods. We newly measured the rotational spectrum of DCOOCH3 in the laboratory of the Jet Propulsion Laboratory in the frequency range of 0.85 to 1.5 THz. We jointly analyzed the new data with literature data using the rho axis method, which is a tool developed for the spectral analysis of molecules with large-amplitude internal CH3 rotors. Results. We fit 27 spectroscopic constants of DCOOCH3 to 3763 transitions with highest values of J = 69 and Ka = 36 of the ground torsional state with a standard (unitless) deviation of 0.97. With respect to previous work, this is a significantly better result that was obtained with 2060 more transitions, and we also achieved a better accuracy for the new parameter values.This research was supported by the FIS2011-28738-C02-02 project (MINECO, Spain), the French PCMI (Programme National de Physique Chimie du Milieu Interstellaire), and the National Natural Science Foundation of China (Grant No. 11174098). M.C. acknowledges the research stay at the Universite Paris Diderot under the Guest Faculty programme in May 2014. Portions of this paper present research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Government sponsorship is acknowledged

Equivalent rotations associated with the permutation inversion group revisited: symmetry projection of the rovibrational functions of methane

In this work the analysis of the equivalent rotations from the permutation inversion group formalism is revisited. We emphasize that explicit knowledge of changes in the Euler angles are not required in order to determine the trans- formation that a given symmetry operation causes to the rotational functions when dealing with the permutation inversion group formalism. Indeed, matrix elements of the equivalent rotations are provided by a single Wigner’s D(j)(R) function. Taking advantage of this, we propose a symmetry projection approach to build the rovibrational functions of methane. This approach focus on the rele- vance of the isomorphism between permutations and equivalent rotations. In our method, symmetry adapted functions are obtained by simultaneous diagonaliza- tion of a set of commuting operators, whose representation is given in terms of direct products of Wigner’s D functions and vibrational matrix representations provided by a local scheme. The proposed approach is general and permits to ob- tain in a systematic fashion an orthonormal set of symmetry-projected functions, with good total angular momentum, and carrying the irreducible representations of the molecular symmetry groupThis work has partially been supported by CONACyT, Mexico. This work has also been partially supported by the Spanish MEC and by European regional development funds (FEDER) under project CPAN-Ingenio (CSD2007-00042), and by the Junta de Andalucia (projects P07-FQM-02962 and P07-FQM-03014)

A theoretical-spectroscopy, ab-initio-based study of the electronic ground state of 121SbH3

For the stibine isotopologue (SbH3)-Sb-121, we report improved theoretical calculations of the vibrational energies below 8000 cm- and simulations of the rovibrational spectrum in the 0-8000 cm(-1) region. The calculations are based on a refined ab initio potential energy surface and on a new dipole moment surface obtained at the coupled cluster CCSD(T) level. The theoretical results are compared with the available experimental data in order to validate the ab initio surfaces and the TROVE computational method [Yurchenko SN, Thiel vv, Jensen P.J mol Spectrosc 2007;245:126-40] for calculating rovibrational energies and simulating rovibrational spectra of arbitrary molecules in isolated electronic states. A number of predicted vibrational energies of (SbH3)-Sb-121 are provided in order to stimulate new experimental investigations of stibine. The localmode character of the vibrations in stibine is demonstrated through an analysis of the results in terms of local-mode theor