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Papers by Miguel Carvajal
Journal of Raman Spectroscopy
We present an accurate simulation of the Raman spectrum of the carbon dioxide molecule in the 115... more We present an accurate simulation of the Raman spectrum of the carbon dioxide molecule in the 1150-1500 cm −1 spectral range, comparing the results obtained using the three polyad schemes found in the literature of this molecule. The description of the molecule with the algebraic U 1 (2) × U(3) × U 2 (2) local model encompasses both stretching and bending degrees of freedom. A detailed analysis of the Hamiltonian interactions for the three polyad schemes provides fittings with root mean square deviations in the range 0.14-0.20 cm −1 , involving 19 parameters taking into account the 178 experimental term energies found in the literature. Using a limited subset of 9 experimental transition moments, we optimize 5 partial derivatives of the mean polarizability and simulate the Raman spectrum of CO 2 for the three polyad schemes. Comparing the calculated results with the experimental spectrum, we obtain an overall good agreement for the three polyads. However, an inspection in detail of the spectrum seems to show a slight preference for polyad P 212 albeit not due to the interaction characterizing the polyad but due to anharmonic effects and energy distribution. Finally, we assess the effect of the Fermi resonance over CO 2 Raman line intensities. KEYWORDS algebraic approach, carbon dioxide, polarizabilities, polyads, Raman spectrum This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
The Journal of Physical Chemistry A, 2015
A novel model for the analysis of the rovibrational structure of a molecule based on anharmonic l... more A novel model for the analysis of the rovibrational structure of a molecule based on anharmonic ladder operators associated with the vibrational degrees of freedom is presented. This is devised as an alternative method for the global spectral analysis of rovibrational data considering vibrational anharmonicities from the outset. The present method is thought up with an effective rovibrational Hamiltonian written in terms of angular momentum components and anharmonic Morse ladder operators, associated with rotational and vibrational degrees of freedom, respectively. The resulting Hamiltonian is diagonalized in a symmetry-adapted basis set expressed as a product of rotational states and individual 1D-Morse wave functions for each local vibrational degree of freedom. This approach has been successfully applied to the study of the vibrational structure (up to polyad 14) and the rovibrational structure (up to polyad 2 and J(max) = 20) of hydrogen sulfide. It was shown that this new global analysis formalism is able to reduce considerably the number of fitted parameters with respect to the spectral analysis carried out for separate polyads.
Physical Review A, 2000
A general formalism for constructing configuration localized states for one-dimensional potential... more 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 12 C 16 O is studied as a way to test the results obtained for different potentials in connection with their ability to model the anharmonicity.
Physical Review A - PHYS REV A, 2000
A general formalism for constructing configuration localized states for one-dimensional potential... more 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 12C16O is studied as a way to test the results obtained for different potentials in connection with their ability to model the anharmonicity.
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Monthly Notices of the Royal Astronomical Society
Isocyanic acid (HNCO) is a simple molecule with a potential to form prebiotic and complex organic... more Isocyanic acid (HNCO) is a simple molecule with a potential to form prebiotic and complex organic species. Using a spectral survey collected with the Atacama Pathfinder EXperiment, in this work we report the detection of 42 transitions of HNCO in the hot molecular core/outflow G331.512-0.103 (hereafter G331). The spectral lines were observed in the frequency interval ∼160–355 GHz. By means of Local Thermodynamic Equilibrium analyses, applying the rotational diagram method, we studied the excitation conditions of HNCO. The excitation temperature and column density are estimated to be Tex= 58.8 ± 2.7 K and N = (3.7 ± 0.5) × 1015 cm−2, considering beam dilution effects. The derived relative abundance is between (3.8 ± 0.5) × 10−9 and (1.4 ± 0.2) × 10−8. In comparison with other hot molecular cores, our column densities and abundances are in agreement. An update of the internal partition functions of the four CHNO isomers: HNCO; cyanic acid, HOCN; fulminic acid, HCNO; and isofulminic ac...
Journal of Quantitative Spectroscopy and Radiative Transfer
The Journal of Physical Chemistry A
The Journal of Physical Chemistry A
In this document, we present the procedure we follow to obtain the bending energy functional for ... more In this document, we present the procedure we follow to obtain the bending energy functional for HCN and HNC, as well as the description of the eective frequency tting method. To complement the discussions in the main text, we also show here the results obtained from the application to levels with vibrational angular momenta dierent from zero.
Astronomy & Astrophysics
We emphasize that the completeness of the partition function, that is, the use of a converged par... more We emphasize that the completeness of the partition function, that is, the use of a converged partition function at the typical temperature range of the survey, is very important to decrease the uncertainty on this quantity and thus to derive reliable interstellar molecular densities. In that context, we show how the use of different approximations for the rovibrational partition function together with some interpolation and/or extrapolation procedures may affect the estimate of the interstellar molecular column density. For that purpose, we apply the partition function calculations to astronomical observations performed with the IRAM-30 m telescope towards the NGC 7538–IRS1 source of two N-bearing molecules: isocyanic acid (HNCO, a quasilinear molecule) and methyl cyanide (CH3CN, a symmetric top molecule). The case of methyl formate (HCOOCH3), which is an asymmetric top O-bearing molecule containing an internal rotor is also discussed. Our analysis shows that the use of different p...
The Journal of Physical Chemistry A, 2016
1 Er Congreso Nacional De Astrofisica Molecular Una Vision General Del Potencial De Los Grupos De Quimica Espanoles Anters Los Nuevos Desafios De La Astrofisica, 2003
ABSTRACT Variational calculations of the vibrational energies of the non-rigid and semirigid XY3 ... more ABSTRACT Variational calculations of the vibrational energies of the non-rigid and semirigid XY3 molecules, as ammonia and phosphine respectively, have been carried out [1,2]. In the procedure used is emphasized the umbrella motion due to the corresponding coordinate, for pyramidal non-rigid XY3 molecules, is the responsible of the torsional tunneling between different minima of the Potential Energy Surfaces. For the NH3 analytical potential energy surfaces were constructed from CCSD(T)/aug-cc-pVTZ ab initio data augmented by the results obtained by extrapolating CCSD(T)/aug-cc-pVXZ (X=T,Q,5) results to the complete basis set limit and adding corrections for core-valence correlation and relativistic effects. The vibrational energies were calculated by employing a kinetic energy operator expressed in terms of linearized internal coordinates. The exact internal coordinates were expressed as sixth-order Taylor expansions in the linearized coordinates. In the present work we show the latter improvement in the calculated vibrational energies with respect to the latter report [1]. This work is supported by the European Commission through contract no. HPRN-CT-2000-00022 ``Spectroscopy of Highly Excited Rovibrational States''.
The experimental spectra of 13C2-methyl formate w the microwave and sub-mm energy ranges (4-20GHz... more The experimental spectra of 13C2-methyl formate w the microwave and sub-mm energy ranges (4-20GHz, 8-80GHz, 150-700GHz). The spectra were analyzed using the Rho-Axis Method (RAM), which takes the CH3 internal rotation and the coupling between internal rotation and global rotation into account. (6 data files).
New radiotelescopes, working in the submillimeter range, will be operating in the next few years:... more New radiotelescopes, working in the submillimeter range, will be operating in the next few years: ALMA, Herschel, and SOFIA. A large amount of laboratory work is required in order to account for the increased resolution and accuracy needed to analyze the numerous data which will be obtained with these new instruments. There is a strong interest of the astrophysical community in isotopic species for two main reasons: (i) Their detection provides us with key information about interstellar chemical modeling, especially for complex organic molecules, like methyl formate, as their formation mechanisms is not well understood yet. (ii) They are responsible for a large fraction of U-lines and their assignments are necessary to allow the detection of new species. In this context we continue a systematic study of the isotopic species of methyl formate (HCOOCH_3) initiated with H^{13}COOCH_3. Our next investigation of HCOO^{13}CH_3 allowed us the detection of 500 lines in Orion. The treatment ...
The two 18O isotopic species of methyl formate were measur analysed up to 660GHz. The treatment o... more The two 18O isotopic species of methyl formate were measur analysed up to 660GHz. The treatment of the internal rotation motion was made using the Rho-Axis- Method and the BELGI code. 4430 and 3258 lines are assigned for the ground torsional states from the HCO18OCH3 and HC18OOCH3 species, respectively. From these spectral analysis, accurate predictions of line positions and intensities are performed. (2 data files).
Journal of Raman Spectroscopy
We present an accurate simulation of the Raman spectrum of the carbon dioxide molecule in the 115... more We present an accurate simulation of the Raman spectrum of the carbon dioxide molecule in the 1150-1500 cm −1 spectral range, comparing the results obtained using the three polyad schemes found in the literature of this molecule. The description of the molecule with the algebraic U 1 (2) × U(3) × U 2 (2) local model encompasses both stretching and bending degrees of freedom. A detailed analysis of the Hamiltonian interactions for the three polyad schemes provides fittings with root mean square deviations in the range 0.14-0.20 cm −1 , involving 19 parameters taking into account the 178 experimental term energies found in the literature. Using a limited subset of 9 experimental transition moments, we optimize 5 partial derivatives of the mean polarizability and simulate the Raman spectrum of CO 2 for the three polyad schemes. Comparing the calculated results with the experimental spectrum, we obtain an overall good agreement for the three polyads. However, an inspection in detail of the spectrum seems to show a slight preference for polyad P 212 albeit not due to the interaction characterizing the polyad but due to anharmonic effects and energy distribution. Finally, we assess the effect of the Fermi resonance over CO 2 Raman line intensities. KEYWORDS algebraic approach, carbon dioxide, polarizabilities, polyads, Raman spectrum This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
The Journal of Physical Chemistry A, 2015
A novel model for the analysis of the rovibrational structure of a molecule based on anharmonic l... more A novel model for the analysis of the rovibrational structure of a molecule based on anharmonic ladder operators associated with the vibrational degrees of freedom is presented. This is devised as an alternative method for the global spectral analysis of rovibrational data considering vibrational anharmonicities from the outset. The present method is thought up with an effective rovibrational Hamiltonian written in terms of angular momentum components and anharmonic Morse ladder operators, associated with rotational and vibrational degrees of freedom, respectively. The resulting Hamiltonian is diagonalized in a symmetry-adapted basis set expressed as a product of rotational states and individual 1D-Morse wave functions for each local vibrational degree of freedom. This approach has been successfully applied to the study of the vibrational structure (up to polyad 14) and the rovibrational structure (up to polyad 2 and J(max) = 20) of hydrogen sulfide. It was shown that this new global analysis formalism is able to reduce considerably the number of fitted parameters with respect to the spectral analysis carried out for separate polyads.
Physical Review A, 2000
A general formalism for constructing configuration localized states for one-dimensional potential... more 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 12 C 16 O is studied as a way to test the results obtained for different potentials in connection with their ability to model the anharmonicity.
Physical Review A - PHYS REV A, 2000
A general formalism for constructing configuration localized states for one-dimensional potential... more 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 12C16O is studied as a way to test the results obtained for different potentials in connection with their ability to model the anharmonicity.
dialnet.unirioja.es
Acceso de usuarios registrados. Acceso de usuarios registrados Usuario Contraseña. ...
Monthly Notices of the Royal Astronomical Society
Isocyanic acid (HNCO) is a simple molecule with a potential to form prebiotic and complex organic... more Isocyanic acid (HNCO) is a simple molecule with a potential to form prebiotic and complex organic species. Using a spectral survey collected with the Atacama Pathfinder EXperiment, in this work we report the detection of 42 transitions of HNCO in the hot molecular core/outflow G331.512-0.103 (hereafter G331). The spectral lines were observed in the frequency interval ∼160–355 GHz. By means of Local Thermodynamic Equilibrium analyses, applying the rotational diagram method, we studied the excitation conditions of HNCO. The excitation temperature and column density are estimated to be Tex= 58.8 ± 2.7 K and N = (3.7 ± 0.5) × 1015 cm−2, considering beam dilution effects. The derived relative abundance is between (3.8 ± 0.5) × 10−9 and (1.4 ± 0.2) × 10−8. In comparison with other hot molecular cores, our column densities and abundances are in agreement. An update of the internal partition functions of the four CHNO isomers: HNCO; cyanic acid, HOCN; fulminic acid, HCNO; and isofulminic ac...
Journal of Quantitative Spectroscopy and Radiative Transfer
The Journal of Physical Chemistry A
The Journal of Physical Chemistry A
In this document, we present the procedure we follow to obtain the bending energy functional for ... more In this document, we present the procedure we follow to obtain the bending energy functional for HCN and HNC, as well as the description of the eective frequency tting method. To complement the discussions in the main text, we also show here the results obtained from the application to levels with vibrational angular momenta dierent from zero.
Astronomy & Astrophysics
We emphasize that the completeness of the partition function, that is, the use of a converged par... more We emphasize that the completeness of the partition function, that is, the use of a converged partition function at the typical temperature range of the survey, is very important to decrease the uncertainty on this quantity and thus to derive reliable interstellar molecular densities. In that context, we show how the use of different approximations for the rovibrational partition function together with some interpolation and/or extrapolation procedures may affect the estimate of the interstellar molecular column density. For that purpose, we apply the partition function calculations to astronomical observations performed with the IRAM-30 m telescope towards the NGC 7538–IRS1 source of two N-bearing molecules: isocyanic acid (HNCO, a quasilinear molecule) and methyl cyanide (CH3CN, a symmetric top molecule). The case of methyl formate (HCOOCH3), which is an asymmetric top O-bearing molecule containing an internal rotor is also discussed. Our analysis shows that the use of different p...
The Journal of Physical Chemistry A, 2016
1 Er Congreso Nacional De Astrofisica Molecular Una Vision General Del Potencial De Los Grupos De Quimica Espanoles Anters Los Nuevos Desafios De La Astrofisica, 2003
ABSTRACT Variational calculations of the vibrational energies of the non-rigid and semirigid XY3 ... more ABSTRACT Variational calculations of the vibrational energies of the non-rigid and semirigid XY3 molecules, as ammonia and phosphine respectively, have been carried out [1,2]. In the procedure used is emphasized the umbrella motion due to the corresponding coordinate, for pyramidal non-rigid XY3 molecules, is the responsible of the torsional tunneling between different minima of the Potential Energy Surfaces. For the NH3 analytical potential energy surfaces were constructed from CCSD(T)/aug-cc-pVTZ ab initio data augmented by the results obtained by extrapolating CCSD(T)/aug-cc-pVXZ (X=T,Q,5) results to the complete basis set limit and adding corrections for core-valence correlation and relativistic effects. The vibrational energies were calculated by employing a kinetic energy operator expressed in terms of linearized internal coordinates. The exact internal coordinates were expressed as sixth-order Taylor expansions in the linearized coordinates. In the present work we show the latter improvement in the calculated vibrational energies with respect to the latter report [1]. This work is supported by the European Commission through contract no. HPRN-CT-2000-00022 ``Spectroscopy of Highly Excited Rovibrational States''.
The experimental spectra of 13C2-methyl formate w the microwave and sub-mm energy ranges (4-20GHz... more The experimental spectra of 13C2-methyl formate w the microwave and sub-mm energy ranges (4-20GHz, 8-80GHz, 150-700GHz). The spectra were analyzed using the Rho-Axis Method (RAM), which takes the CH3 internal rotation and the coupling between internal rotation and global rotation into account. (6 data files).
New radiotelescopes, working in the submillimeter range, will be operating in the next few years:... more New radiotelescopes, working in the submillimeter range, will be operating in the next few years: ALMA, Herschel, and SOFIA. A large amount of laboratory work is required in order to account for the increased resolution and accuracy needed to analyze the numerous data which will be obtained with these new instruments. There is a strong interest of the astrophysical community in isotopic species for two main reasons: (i) Their detection provides us with key information about interstellar chemical modeling, especially for complex organic molecules, like methyl formate, as their formation mechanisms is not well understood yet. (ii) They are responsible for a large fraction of U-lines and their assignments are necessary to allow the detection of new species. In this context we continue a systematic study of the isotopic species of methyl formate (HCOOCH_3) initiated with H^{13}COOCH_3. Our next investigation of HCOO^{13}CH_3 allowed us the detection of 500 lines in Orion. The treatment ...
The two 18O isotopic species of methyl formate were measur analysed up to 660GHz. The treatment o... more The two 18O isotopic species of methyl formate were measur analysed up to 660GHz. The treatment of the internal rotation motion was made using the Rho-Axis- Method and the BELGI code. 4430 and 3258 lines are assigned for the ground torsional states from the HCO18OCH3 and HC18OOCH3 species, respectively. From these spectral analysis, accurate predictions of line positions and intensities are performed. (2 data files).