The Experts below are selected from a list of 7893 Experts worldwide ranked by ideXlab platform

Paulo Limão-vieira - One of the best experts on this subject based on the ideXlab platform.

  • On the electronic structure of methyl butyrate and methyl valerate
    The European Physical Journal D, 2020
    Co-Authors: Małgorzata A. Śmiałek, Denis Duflot, Nykola C. Jones, Søren Vrønning Hoffmann, Lucia Zuin, M A Macdonald, Nigel J. Mason, Paulo Limão-vieira
    Abstract:

    We present novel results of the analysis of the electronic structure of two aliphatic esters: methyl butyrate and methyl valerate. High-resolution Photoabsorption spectra were collected and analyzed over the energy range 4.0–10.8 eV and showed for both the molecules not only a clear band of the HOMO to LUMO transition, but also vibronic structure associated with the first Rydberg-valence transition. Photoelectron spectra recorded from 9 to over 28 eV revealed many ionization states with the first adiabatic ionization energies found to be 9.977 eV and 9.959 eV for methyl butyrate and methyl valerate, respectively. Ab initio calculations have been performed in order to help assign the Photoabsorption and photoelectron features. Photolysis life times in the atmosphere were calculated revealing that photolysis is not competitive over hydroxyl radical scavenging in the process of removal of these esters from the atmosphere.

  • The electronic excited states of dichloromethane in the 5.8-10.8 eV energy range investigated by experimental and theoretical methods
    Journal of Quantitative Spectroscopy and Radiative Transfer, 2020
    Co-Authors: E. Lange, S V Hoffmann, Małgorzata A. Śmiałek, M J Brunger, A I Lozano, M G P Homem, N. C. Jones, D. Duflot, S. Kumar, Paulo Limão-vieira
    Abstract:

    We present a comprehensive experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectrum of dichloromethane, CH2Cl2, with absolute cross sections determined for the full 5.8–10.8 eV energy-range. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method, restricted to the single and double excitations level (EOM-CCSD), and were used to help analyse the valence and Rydberg structures in the Photoabsorption spectrum. The present spectrum additionally reveals several new features not previously reported in the literature, with particular reference to the valence σ*CCl (10a1) ← nCl (7b2) (11B2 ← X1A1) and (σ*CCl (10a1) ← nCl (9a1) + σ*CH (11a1) ← nCl (7b2)) (11A1 ← X 1A1) transitions at 7.519 and 7.793 eV. A vibrational progression of the CCl2 symmetric stretching, ν'3, and CCl2 scissoring, ν'4 (a1), modes have also been assigned for the first time in the 7.4–8.6 eV energy range. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of dichloromethane in the Earth's atmosphere (0–50 km). Potential energy curves as a function of the C–Cl coordinate, for the four lowest-lying excited A′ and A″ electronic states, have additionally been calculated at the EOM-CCSD level of theory.

  • Valence and lowest Rydberg electronic states of phenol investigated by synchrotron radiation and theoretical methods
    Journal of Chemical Physics, 2016
    Co-Authors: Paulo Limão-vieira, Denis Duflot, S V Hoffmann, Małgorzata A. Śmiałek, D B Jones, E. Lange, F. Ferreira Da Silva, Nykola Jones, M J Brunger
    Abstract:

    We present the experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectra of phenol covering for the first time the full 4.3–10.8 eV energy-range, with absolute cross sections determined. Theoretical calculations on the vertical excitation energies and oscillator strengths were performed using time-dependent density functional theory and the equation-of-motion coupled cluster method restricted to single and double excitations level. These have been used in the assignment of valence and Rydberg transitions of the phenol molecule. The VUV spectrum reveals several new features not previously reported in the literature, with particular reference to the 6.401 eV transition, which is here assigned to the 3sσ/σ∗(OH)←3π(3a″) transition. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of phenol in the earth’s atmosphere (0–50 km).

  • Toluene Valence and Rydberg Excitations as Studied by ab initio Calculations and Vacuum Ultraviolet (VUV) Synchrotron Radiation
    Journal of Physical Chemistry A, 2015
    Co-Authors: C. Serralheiro, Denis Duflot, N. J. Mason, S V Hoffmann, F. Ferreira Da Silva, Nykola Jones, B Mendes, Paulo Limão-vieira
    Abstract:

    The electronic spectroscopy of isolated toluene in the gas phase has been investigated using high-resolution Photoabsorption spectroscopy in the 4.0–10.8 eV energy range, with absolute cross-section measurements derived. We present the first set of ab initio calculations (vertical energies and oscillator strengths), which we use in the assignment of valence and Rydberg transitions of the toluene molecule. The spectrum reveals several new features not previously reported in the literature, with particular relevance to 7.989 and 8.958 eV, which are here tentatively assigned to the π*(17a′) ← σ(15a′) and 1π*(10a″) ← 1π(14a′) transitions, respectively. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of toluene in the upper stratosphere (20–50 km).

  • Limonene: electronic state spectroscopy by high-resolution vacuum ultraviolet Photoabsorption, electron scattering, He(I) photoelectron spectroscopy and ab initio calculations.
    Physical Chemistry Chemical Physics, 2012
    Co-Authors: Małgorzata A. Śmiałek, N. J. Mason, J Delwiche, M.-j. Hubin-franskin, A. M. Ferreira-rodrigues, F. N. Rodrigues, G. G. B. De Souza, D. Duflot, S. Vrønning-hoffmann, Paulo Limão-vieira
    Abstract:

    Electronic state spectroscopy of limonene has been investigated using vacuum ultraviolet Photoabsorption spectroscopy in the energy range 5.0-10.8 eV. The availability of a high resolution photon beam (~0.075 nm) enabled detailed analysis of the vibrational progressions and allowed us to propose, for the first time, new assignments for several Rydberg series. Excited states located in the 7.5-8.4 eV region have been studied for the first time. A He(I) photoelectron spectrum has also been recorded from 8.2 to 9.5 eV and compared to previous low resolution works. A new value of 8.521 ± 0.002 eV for the ground ionic state adiabatic ionisation energy is proposed. Absolute Photoabsorption cross sections were derived in the 10-26 eV range from electron scattering data. All spectra presented in this paper represent the highest resolution data yet reported for limonene. These experiments are complemented by new ab initio calculations performed for the three most abundant conformational isomers of limonene, which we then used in the assignment of the spectral bands.

S V Hoffmann - One of the best experts on this subject based on the ideXlab platform.

  • The electronic excited states of dichloromethane in the 5.8-10.8 eV energy range investigated by experimental and theoretical methods
    Journal of Quantitative Spectroscopy and Radiative Transfer, 2020
    Co-Authors: E. Lange, S V Hoffmann, Małgorzata A. Śmiałek, M J Brunger, A I Lozano, M G P Homem, N. C. Jones, D. Duflot, S. Kumar, Paulo Limão-vieira
    Abstract:

    We present a comprehensive experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectrum of dichloromethane, CH2Cl2, with absolute cross sections determined for the full 5.8–10.8 eV energy-range. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method, restricted to the single and double excitations level (EOM-CCSD), and were used to help analyse the valence and Rydberg structures in the Photoabsorption spectrum. The present spectrum additionally reveals several new features not previously reported in the literature, with particular reference to the valence σ*CCl (10a1) ← nCl (7b2) (11B2 ← X1A1) and (σ*CCl (10a1) ← nCl (9a1) + σ*CH (11a1) ← nCl (7b2)) (11A1 ← X 1A1) transitions at 7.519 and 7.793 eV. A vibrational progression of the CCl2 symmetric stretching, ν'3, and CCl2 scissoring, ν'4 (a1), modes have also been assigned for the first time in the 7.4–8.6 eV energy range. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of dichloromethane in the Earth's atmosphere (0–50 km). Potential energy curves as a function of the C–Cl coordinate, for the four lowest-lying excited A′ and A″ electronic states, have additionally been calculated at the EOM-CCSD level of theory.

  • revisiting the Photoabsorption spectrum of nh3 in the 5 4 10 8 ev energy region
    Journal of Chemical Physics, 2019
    Co-Authors: Denis Duflot, S V Hoffmann, Nykola C. Jones, Manuel J Mendes, P Limaovieira, Ferreira F Da Silva, A I Lozano, Gustavo Garcia
    Abstract:

    We present a comprehensive revisited experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectrum of ammonia, NH3, covering for the first time the full 5.4–10.8 eV energy-range, with absolute cross sections determined. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method restricted to single and double excitation levels and used to help reanalyze the observed Rydberg structures in the Photoabsorption spectrum. The VUV spectrum reveals several new features that are not previously reported in the literature, with particular reference to the vibrational progressions of the (D1E′←X1A1′), the (F1E′←X1A1′), and the (G1A2″←X1A1′) absorption bands. In addition, new Rydberg members have been identified in nda1′←1a2″D′′1A2″←X1A1′, where n > 3 has not been reported before as well as in nde″←1a2″F1E′←X1A1′ and in nsa1′←1a2″G1A2″←X1A1′. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of ammonia in the Earth’s atmosphere (0–50 km).We present a comprehensive revisited experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectrum of ammonia, NH3, covering for the first time the full 5.4–10.8 eV energy-range, with absolute cross sections determined. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method restricted to single and double excitation levels and used to help reanalyze the observed Rydberg structures in the Photoabsorption spectrum. The VUV spectrum reveals several new features that are not previously reported in the literature, with particular reference to the vibrational progressions of the (D1E′←X1A1′), the (F1E′←X1A1′), and the (G1A2″←X1A1′) absorption bands. In addition, new Rydberg members have been identified in nda1′←1a2″D′′1A2″←X1A1′, where n > 3 has not been reported before as well as in nde″←1a2″F1E′←X1A1′ and in nsa1′←1a2″G1A2″←X1A1′. The measured absolute Photoabsorption cross sections have been...

  • electronic structure and vuv Photoabsorption measurements of thiophene
    Journal of Chemical Physics, 2019
    Co-Authors: D B Jones, S V Hoffmann, Nykola C. Jones, Manuel J Mendes, P Limaovieira, Ferreira F Da Silva, M J Brunger
    Abstract:

    The absolute Photoabsorption cross sections for thiophene in the 5.0-10.7 eV range were measured using synchrotron radiation. New theoretical calculations performed at the time-dependent density functional theory level were used to qualitatively interpret the recorded Photoabsorption spectrum. The calculations facilitated a re-analysis of the observed vibronic and Rydberg structures in the Photoabsorption spectrum. Here a number of features have been re-assigned, while a number of other features have been assigned for the first time. This represents the most comprehensive and self-consistent assignment of the thiophene high-resolution Photoabsorption spectrum to date.

  • Valence and lowest Rydberg electronic states of phenol investigated by synchrotron radiation and theoretical methods
    Journal of Chemical Physics, 2016
    Co-Authors: Paulo Limão-vieira, Denis Duflot, S V Hoffmann, Małgorzata A. Śmiałek, D B Jones, E. Lange, F. Ferreira Da Silva, Nykola Jones, M J Brunger
    Abstract:

    We present the experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectra of phenol covering for the first time the full 4.3–10.8 eV energy-range, with absolute cross sections determined. Theoretical calculations on the vertical excitation energies and oscillator strengths were performed using time-dependent density functional theory and the equation-of-motion coupled cluster method restricted to single and double excitations level. These have been used in the assignment of valence and Rydberg transitions of the phenol molecule. The VUV spectrum reveals several new features not previously reported in the literature, with particular reference to the 6.401 eV transition, which is here assigned to the 3sσ/σ∗(OH)←3π(3a″) transition. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of phenol in the earth’s atmosphere (0–50 km).

  • Toluene Valence and Rydberg Excitations as Studied by ab initio Calculations and Vacuum Ultraviolet (VUV) Synchrotron Radiation
    Journal of Physical Chemistry A, 2015
    Co-Authors: C. Serralheiro, Denis Duflot, N. J. Mason, S V Hoffmann, F. Ferreira Da Silva, Nykola Jones, B Mendes, Paulo Limão-vieira
    Abstract:

    The electronic spectroscopy of isolated toluene in the gas phase has been investigated using high-resolution Photoabsorption spectroscopy in the 4.0–10.8 eV energy range, with absolute cross-section measurements derived. We present the first set of ab initio calculations (vertical energies and oscillator strengths), which we use in the assignment of valence and Rydberg transitions of the toluene molecule. The spectrum reveals several new features not previously reported in the literature, with particular relevance to 7.989 and 8.958 eV, which are here tentatively assigned to the π*(17a′) ← σ(15a′) and 1π*(10a″) ← 1π(14a′) transitions, respectively. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of toluene in the upper stratosphere (20–50 km).

J Delwiche - One of the best experts on this subject based on the ideXlab platform.

  • valence and ionic lowest lying electronic states of ethyl formate as studied by high resolution vacuum ultraviolet Photoabsorption he i photoelectron spectroscopy and ab initio calculations
    Journal of Physical Chemistry A, 2014
    Co-Authors: Malgorzata A śmialek, Denis Duflot, N. J. Mason, S V Hoffmann, Nykola C. Jones, M łabuda, Julien Guthmuller, Mariejeanne Hubinfranskin, J Delwiche, P Limaovieira
    Abstract:

    The highest resolution vacuum ultraviolet Photoabsorption spectrum of ethyl formate, C2H5OCHO, yet reported is presented over the wavelength range 115.0–275.5 nm (10.75–4.5 eV) revealing several new spectral features. Valence and Rydberg transitions and their associated vibronic series, observed in the Photoabsorption spectrum, have been assigned in accordance with new ab initio calculations of the vertical excitation energies and oscillator strengths. Calculations have also been carried out to determine the ionization energies and fine structure of the lowest ionic state of ethyl formate and are compared with a newly recorded He(I) photoelectron spectrum (from 10.1 to 16.1 eV). New vibrational structure is observed in the first photoelectron band. The Photoabsorption cross sections have been used to calculate the photolysis lifetime of ethyl formate in the upper stratosphere (20–50 km).

  • Limonene: electronic state spectroscopy by high-resolution vacuum ultraviolet Photoabsorption, electron scattering, He(I) photoelectron spectroscopy and ab initio calculations.
    Physical Chemistry Chemical Physics, 2012
    Co-Authors: Małgorzata A. Śmiałek, N. J. Mason, J Delwiche, M.-j. Hubin-franskin, A. M. Ferreira-rodrigues, F. N. Rodrigues, G. G. B. De Souza, D. Duflot, S. Vrønning-hoffmann, Paulo Limão-vieira
    Abstract:

    Electronic state spectroscopy of limonene has been investigated using vacuum ultraviolet Photoabsorption spectroscopy in the energy range 5.0-10.8 eV. The availability of a high resolution photon beam (~0.075 nm) enabled detailed analysis of the vibrational progressions and allowed us to propose, for the first time, new assignments for several Rydberg series. Excited states located in the 7.5-8.4 eV region have been studied for the first time. A He(I) photoelectron spectrum has also been recorded from 8.2 to 9.5 eV and compared to previous low resolution works. A new value of 8.521 ± 0.002 eV for the ground ionic state adiabatic ionisation energy is proposed. Absolute Photoabsorption cross sections were derived in the 10-26 eV range from electron scattering data. All spectra presented in this paper represent the highest resolution data yet reported for limonene. These experiments are complemented by new ab initio calculations performed for the three most abundant conformational isomers of limonene, which we then used in the assignment of the spectral bands.

  • Electronic state spectroscopy of methyl formate probed by high resolution VUV Photoabsorption, He(i) photoelectron spectroscopy and ab initio calculations.
    Physical Chemistry Chemical Physics, 2010
    Co-Authors: Y. Nunes, Denis Duflot, N. J. Mason, S V Hoffmann, J Delwiche, G. Martins, M.-j. Hubin-franskin, Paulo Limão-vieira
    Abstract:

    The first ab initio calculations of the vertical excitation energies and oscillator strengths are presented for the neutral electronic transitions of methyl formate, C(2)H(4)O(2). The highest resolution VUV Photoabsorption spectrum of the molecule yet reported is presented over the wavelength range 115 to 310 nm (10.8 to 4.0 eV) revealing several new spectral features. Valence and Rydberg transitions and their associated vibronic series, observed in the Photoabsorption spectrum, have been assigned in accordance with new theoretical results. The calculations have been carried out to determine the excitation energies of the lowest energy ionic states of methyl formate and are compared with a newly recorded He(i) photoelectron spectrum (10.4 to 17.0 eV). New vibrational structure is observed in the first photoelectron band. The Photoabsorption cross-sections have been used to calculate the photolysis lifetime of methyl formate in the upper stratosphere (20-50 km).

  • Valence shell electronic spectroscopy of isoprene studied by theoretical calculations and by electron scattering, photoelectron, and absolute Photoabsorption measurements.
    Physical Chemistry Chemical Physics, 2009
    Co-Authors: G. Martins, Denis Duflot, N. J. Mason, S V Hoffmann, A. M. Ferreira-rodrigues, F. N. Rodrigues, G. G. B. De Souza, S. Eden, J.-p. Flament, J Delwiche
    Abstract:

    The first ab initio calculations (vertical energies and oscillator strengths) are reported for the neutral electronic transitions of isoprene (2-methyl-1,3-butadiene), CH(2)CHC(CH(3))CH(2). The VUV Photoabsorption spectroscopy of the molecule is presented in the energy range 4.6 to 10.8 eV (270-125 nm) with the highest resolution yet reported above 6.05 eV, revealing new spectral features. Valence and Rydberg transitions have been assigned in accordance with the theoretical results and the associated vibronic series have been analysed. The absolute Photoabsorption cross sections at energies below 6.89 eV have been used to calculate the photolysis lifetime of isoprene in the upper stratosphere (20-50 km). Electron energy loss spectroscopy (EELS) measurements have enabled further Photoabsorption cross sections to be derived in the range 9-28 eV. The first ab initio calculations have been carried out to determine excitation energies to the lowest energy ionic states of isoprene. The calculations are compared with the He(i) photoelectron spectrum (8 to 17 eV) and new vibrational structure is observed in the first photoelectron band.

  • Photoabsorption measurements and theoretical calculations of the electronic state spectroscopy of propionic, butyric, and valeric acids.
    Physical Chemistry Chemical Physics, 2009
    Co-Authors: A. Vicente, N. J. Mason, S V Hoffmann, S. Eden, R. Antunes, D. Almeida, I. J. A. Franco, D. Duflot, S. Canneaux, J Delwiche
    Abstract:

    Absolute Photoabsorption cross sections of propionic (C2H5COOH), butyric (C3H7COOH), and valeric (C4H9COOH) acids have been measured from the dissociative pi*

N. J. Mason - One of the best experts on this subject based on the ideXlab platform.

  • Toluene Valence and Rydberg Excitations as Studied by ab initio Calculations and Vacuum Ultraviolet (VUV) Synchrotron Radiation
    Journal of Physical Chemistry A, 2015
    Co-Authors: C. Serralheiro, Denis Duflot, N. J. Mason, S V Hoffmann, F. Ferreira Da Silva, Nykola Jones, B Mendes, Paulo Limão-vieira
    Abstract:

    The electronic spectroscopy of isolated toluene in the gas phase has been investigated using high-resolution Photoabsorption spectroscopy in the 4.0–10.8 eV energy range, with absolute cross-section measurements derived. We present the first set of ab initio calculations (vertical energies and oscillator strengths), which we use in the assignment of valence and Rydberg transitions of the toluene molecule. The spectrum reveals several new features not previously reported in the literature, with particular relevance to 7.989 and 8.958 eV, which are here tentatively assigned to the π*(17a′) ← σ(15a′) and 1π*(10a″) ← 1π(14a′) transitions, respectively. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of toluene in the upper stratosphere (20–50 km).

  • valence and ionic lowest lying electronic states of ethyl formate as studied by high resolution vacuum ultraviolet Photoabsorption he i photoelectron spectroscopy and ab initio calculations
    Journal of Physical Chemistry A, 2014
    Co-Authors: Malgorzata A śmialek, Denis Duflot, N. J. Mason, S V Hoffmann, Nykola C. Jones, M łabuda, Julien Guthmuller, Mariejeanne Hubinfranskin, J Delwiche, P Limaovieira
    Abstract:

    The highest resolution vacuum ultraviolet Photoabsorption spectrum of ethyl formate, C2H5OCHO, yet reported is presented over the wavelength range 115.0–275.5 nm (10.75–4.5 eV) revealing several new spectral features. Valence and Rydberg transitions and their associated vibronic series, observed in the Photoabsorption spectrum, have been assigned in accordance with new ab initio calculations of the vertical excitation energies and oscillator strengths. Calculations have also been carried out to determine the ionization energies and fine structure of the lowest ionic state of ethyl formate and are compared with a newly recorded He(I) photoelectron spectrum (from 10.1 to 16.1 eV). New vibrational structure is observed in the first photoelectron band. The Photoabsorption cross sections have been used to calculate the photolysis lifetime of ethyl formate in the upper stratosphere (20–50 km).

  • Limonene: electronic state spectroscopy by high-resolution vacuum ultraviolet Photoabsorption, electron scattering, He(I) photoelectron spectroscopy and ab initio calculations.
    Physical Chemistry Chemical Physics, 2012
    Co-Authors: Małgorzata A. Śmiałek, N. J. Mason, J Delwiche, M.-j. Hubin-franskin, A. M. Ferreira-rodrigues, F. N. Rodrigues, G. G. B. De Souza, D. Duflot, S. Vrønning-hoffmann, Paulo Limão-vieira
    Abstract:

    Electronic state spectroscopy of limonene has been investigated using vacuum ultraviolet Photoabsorption spectroscopy in the energy range 5.0-10.8 eV. The availability of a high resolution photon beam (~0.075 nm) enabled detailed analysis of the vibrational progressions and allowed us to propose, for the first time, new assignments for several Rydberg series. Excited states located in the 7.5-8.4 eV region have been studied for the first time. A He(I) photoelectron spectrum has also been recorded from 8.2 to 9.5 eV and compared to previous low resolution works. A new value of 8.521 ± 0.002 eV for the ground ionic state adiabatic ionisation energy is proposed. Absolute Photoabsorption cross sections were derived in the 10-26 eV range from electron scattering data. All spectra presented in this paper represent the highest resolution data yet reported for limonene. These experiments are complemented by new ab initio calculations performed for the three most abundant conformational isomers of limonene, which we then used in the assignment of the spectral bands.

  • Electronic state spectroscopy of 1,4-pentadiene as studied by VUV Photoabsorption spectroscopy and ab initio calculations
    Journal of Physical Chemistry A, 2012
    Co-Authors: Salvatore Serio, Y. Nunes, Denis Duflot, N. J. Mason, S V Hoffmann, Paulo Limão-vieira
    Abstract:

    We present high resolution VUV Photoabsorption spectra of 1,4-pentadiene, C(5)H(8), over the wavelength range 115-247 nm (10.8-5.0 eV). These spectra reveal several new features not previously reported in the literature. These measurements are complemented by the first ab initio calculations for the three most abundant conformational isomers of 1,4-pentadiene, C(5)H(8), which we then use in the assignment of valence and Rydberg transitions. Calculations of the two lowest energy ionic states of 1,4-pentadiene are also presented and compared with the experimental data available in the literature. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of 1,4-pentadiene in the upper stratosphere (20-50 km).

  • Electronic state spectroscopy of methyl formate probed by high resolution VUV Photoabsorption, He(i) photoelectron spectroscopy and ab initio calculations.
    Physical Chemistry Chemical Physics, 2010
    Co-Authors: Y. Nunes, Denis Duflot, N. J. Mason, S V Hoffmann, J Delwiche, G. Martins, M.-j. Hubin-franskin, Paulo Limão-vieira
    Abstract:

    The first ab initio calculations of the vertical excitation energies and oscillator strengths are presented for the neutral electronic transitions of methyl formate, C(2)H(4)O(2). The highest resolution VUV Photoabsorption spectrum of the molecule yet reported is presented over the wavelength range 115 to 310 nm (10.8 to 4.0 eV) revealing several new spectral features. Valence and Rydberg transitions and their associated vibronic series, observed in the Photoabsorption spectrum, have been assigned in accordance with new theoretical results. The calculations have been carried out to determine the excitation energies of the lowest energy ionic states of methyl formate and are compared with a newly recorded He(i) photoelectron spectrum (10.4 to 17.0 eV). New vibrational structure is observed in the first photoelectron band. The Photoabsorption cross-sections have been used to calculate the photolysis lifetime of methyl formate in the upper stratosphere (20-50 km).

Denis Duflot - One of the best experts on this subject based on the ideXlab platform.

  • On the electronic structure of methyl butyrate and methyl valerate
    The European Physical Journal D, 2020
    Co-Authors: Małgorzata A. Śmiałek, Denis Duflot, Nykola C. Jones, Søren Vrønning Hoffmann, Lucia Zuin, M A Macdonald, Nigel J. Mason, Paulo Limão-vieira
    Abstract:

    We present novel results of the analysis of the electronic structure of two aliphatic esters: methyl butyrate and methyl valerate. High-resolution Photoabsorption spectra were collected and analyzed over the energy range 4.0–10.8 eV and showed for both the molecules not only a clear band of the HOMO to LUMO transition, but also vibronic structure associated with the first Rydberg-valence transition. Photoelectron spectra recorded from 9 to over 28 eV revealed many ionization states with the first adiabatic ionization energies found to be 9.977 eV and 9.959 eV for methyl butyrate and methyl valerate, respectively. Ab initio calculations have been performed in order to help assign the Photoabsorption and photoelectron features. Photolysis life times in the atmosphere were calculated revealing that photolysis is not competitive over hydroxyl radical scavenging in the process of removal of these esters from the atmosphere.

  • revisiting the Photoabsorption spectrum of nh3 in the 5 4 10 8 ev energy region
    Journal of Chemical Physics, 2019
    Co-Authors: Denis Duflot, S V Hoffmann, Nykola C. Jones, Manuel J Mendes, P Limaovieira, Ferreira F Da Silva, A I Lozano, Gustavo Garcia
    Abstract:

    We present a comprehensive revisited experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectrum of ammonia, NH3, covering for the first time the full 5.4–10.8 eV energy-range, with absolute cross sections determined. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method restricted to single and double excitation levels and used to help reanalyze the observed Rydberg structures in the Photoabsorption spectrum. The VUV spectrum reveals several new features that are not previously reported in the literature, with particular reference to the vibrational progressions of the (D1E′←X1A1′), the (F1E′←X1A1′), and the (G1A2″←X1A1′) absorption bands. In addition, new Rydberg members have been identified in nda1′←1a2″D′′1A2″←X1A1′, where n > 3 has not been reported before as well as in nde″←1a2″F1E′←X1A1′ and in nsa1′←1a2″G1A2″←X1A1′. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of ammonia in the Earth’s atmosphere (0–50 km).We present a comprehensive revisited experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectrum of ammonia, NH3, covering for the first time the full 5.4–10.8 eV energy-range, with absolute cross sections determined. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method restricted to single and double excitation levels and used to help reanalyze the observed Rydberg structures in the Photoabsorption spectrum. The VUV spectrum reveals several new features that are not previously reported in the literature, with particular reference to the vibrational progressions of the (D1E′←X1A1′), the (F1E′←X1A1′), and the (G1A2″←X1A1′) absorption bands. In addition, new Rydberg members have been identified in nda1′←1a2″D′′1A2″←X1A1′, where n > 3 has not been reported before as well as in nde″←1a2″F1E′←X1A1′ and in nsa1′←1a2″G1A2″←X1A1′. The measured absolute Photoabsorption cross sections have been...

  • Valence and lowest Rydberg electronic states of phenol investigated by synchrotron radiation and theoretical methods
    Journal of Chemical Physics, 2016
    Co-Authors: Paulo Limão-vieira, Denis Duflot, S V Hoffmann, Małgorzata A. Śmiałek, D B Jones, E. Lange, F. Ferreira Da Silva, Nykola Jones, M J Brunger
    Abstract:

    We present the experimental high-resolution vacuum ultraviolet (VUV) Photoabsorption spectra of phenol covering for the first time the full 4.3–10.8 eV energy-range, with absolute cross sections determined. Theoretical calculations on the vertical excitation energies and oscillator strengths were performed using time-dependent density functional theory and the equation-of-motion coupled cluster method restricted to single and double excitations level. These have been used in the assignment of valence and Rydberg transitions of the phenol molecule. The VUV spectrum reveals several new features not previously reported in the literature, with particular reference to the 6.401 eV transition, which is here assigned to the 3sσ/σ∗(OH)←3π(3a″) transition. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of phenol in the earth’s atmosphere (0–50 km).

  • Toluene Valence and Rydberg Excitations as Studied by ab initio Calculations and Vacuum Ultraviolet (VUV) Synchrotron Radiation
    Journal of Physical Chemistry A, 2015
    Co-Authors: C. Serralheiro, Denis Duflot, N. J. Mason, S V Hoffmann, F. Ferreira Da Silva, Nykola Jones, B Mendes, Paulo Limão-vieira
    Abstract:

    The electronic spectroscopy of isolated toluene in the gas phase has been investigated using high-resolution Photoabsorption spectroscopy in the 4.0–10.8 eV energy range, with absolute cross-section measurements derived. We present the first set of ab initio calculations (vertical energies and oscillator strengths), which we use in the assignment of valence and Rydberg transitions of the toluene molecule. The spectrum reveals several new features not previously reported in the literature, with particular relevance to 7.989 and 8.958 eV, which are here tentatively assigned to the π*(17a′) ← σ(15a′) and 1π*(10a″) ← 1π(14a′) transitions, respectively. The measured absolute Photoabsorption cross sections have been used to calculate the photolysis lifetime of toluene in the upper stratosphere (20–50 km).

  • valence and ionic lowest lying electronic states of ethyl formate as studied by high resolution vacuum ultraviolet Photoabsorption he i photoelectron spectroscopy and ab initio calculations
    Journal of Physical Chemistry A, 2014
    Co-Authors: Malgorzata A śmialek, Denis Duflot, N. J. Mason, S V Hoffmann, Nykola C. Jones, M łabuda, Julien Guthmuller, Mariejeanne Hubinfranskin, J Delwiche, P Limaovieira
    Abstract:

    The highest resolution vacuum ultraviolet Photoabsorption spectrum of ethyl formate, C2H5OCHO, yet reported is presented over the wavelength range 115.0–275.5 nm (10.75–4.5 eV) revealing several new spectral features. Valence and Rydberg transitions and their associated vibronic series, observed in the Photoabsorption spectrum, have been assigned in accordance with new ab initio calculations of the vertical excitation energies and oscillator strengths. Calculations have also been carried out to determine the ionization energies and fine structure of the lowest ionic state of ethyl formate and are compared with a newly recorded He(I) photoelectron spectrum (from 10.1 to 16.1 eV). New vibrational structure is observed in the first photoelectron band. The Photoabsorption cross sections have been used to calculate the photolysis lifetime of ethyl formate in the upper stratosphere (20–50 km).