The adsorption of a series of atoms and small molecules and radicals (H, C, N, O, NH, OH, H2O, CH... more The adsorption of a series of atoms and small molecules and radicals (H, C, N, O, NH, OH, H2O, CH3, and NH3) on hexagonal crystalline and amorphous ice clusters were obtained via classical molecular dynamics and electronic structure methods. The geometry and binding energies were calculated using a QMHigh:QMLow hybrid method on model clusters. Several combination of basis sets, density functionals and semi-empirical methods were compared and tested against previous works. More accurate binding energies were also refined via single point Coupled Cluster calculations. Most species, except carbon atom, physisorb on the surface, leading to rather small binding energies. The carbon atom forms a COH2 molecule and in some cases leads to the formation of a COH-H3O+ complex. Amorphous ices are characterized by slightly stronger binding energies than the crystalline phase. A major result of this work is to also access the dispersion of the binding energies since a variety of adsorption sites ...
The emission and use of synchrotron radiation (SR) are powerful tools for performing state-of-the... more The emission and use of synchrotron radiation (SR) are powerful tools for performing state-of-the art research at the fundamental and applied levels, benefiting a diversity of research areas across medicine, molecular and cell biology, condensed matter physics, nanotechnology, cultural heritage, environmental science, atomic and molecular physics, among many others.
Electronic state spectroscopy of CH3COOH has been investigated using Vacuum UltraViolet (VUV) pho... more Electronic state spectroscopy of CH3COOH has been investigated using Vacuum UltraViolet (VUV) photo-absorption spectroscopy in the energy range 3.5–10.6eV. The availability of a high-resolution photon beam (∼0.075nm) has allowed 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 10–14eV region have been studied
The journal of physical chemistry letters, Jan 5, 2017
Photoionization of a buckminsterfullerene ion is investigated using an ion trap and a merged beam... more Photoionization of a buckminsterfullerene ion is investigated using an ion trap and a merged beam setup coupled to synchrotron radiation beamlines and compared to theoretical calculations. Absolute measurements derived from the ion trap experiment allow discrepancies concerning the photoionization cross section of C60(+) to be solved.
The journal of physical chemistry. A, Jan 26, 2016
Electron energy loss (EEL) spectra of GeF4 have been measured with incident electrons at 100 eV f... more Electron energy loss (EEL) spectra of GeF4 have been measured with incident electrons at 100 eV for 5° scattering angle and at 30 eV for 30° scattering angle, while sweeping the energy loss over the range 7.0-21.0 eV. Low-lying excited triplet, singlet, valence and Rydberg states are investigated and the assignments supported by quantum chemical ab initio calculations. This provides the first comprehensive investigation of all singlet and triplet excited electronic states of germanium tetrafluoride up to the first ionisation energy. The Rydberg series converging to the (lowest) ionisation energy limits of GeF4 are also identified according to the magnitude of the quantum defects (δ).
To be published in the Journal of Chemical Physics The C2H photodissociation processes have been ... more To be published in the Journal of Chemical Physics The C2H photodissociation processes have been studied using ab initio multireference perturbative Configuration Interaction (Cl) methods. The calculated structural parameters of the two linear lowest lying states X2l:+ and A2TI were found to be in good agreement with previous theoretical and experimental works.' Construction of the correlation diagram indicates that C2H cannot photodissociate into C + CH. Therefore, two-dimensional potential energy surfaces of the six lowest lying A' and A" doublet states have been calculated as functions of the bond angle and the C-H bond distance, keeping the CC distance at the equilibrium C2H value. It appears that the 1 2A', 2 2A' and 1 2A" states correlating to the X2l:,+ and A2TI states in linear geometry remain bound at ail angles, whereas the 3 2A', 4 2A' and 4 2A" are dissociative. However, the structure of the energy surfaces is complicated by the presence of numerous avoided crossings between these states. Transition dipole moments connecting the excited states with the X2l:,+ and A2TI states have been also obtained in linear geometry. They were calculated to be very weak, leading JO the conclusion that the photodissociation rate of C2H will be negligeable below 7 eV. Higher lying states, including Rydberg states, were not considered here, since they cannot dissociate direct! y into C2 + H.
Ab initio electronic structure theory (MCSCF+CI) has been used to determine the more important fe... more Ab initio electronic structure theory (MCSCF+CI) has been used to determine the more important features of the potential energy surface for the simple isomerization reaction HCSi ↠ HSiC.Our preliminary results indicate that H-Si-C has a bent structure while H-C-Si is linear. More, the H-Si-C ground state is 2A’ and it is 2&Pgr; for H-C-Si.Potential barriers for isomerization are calculated. Geometries, energies and dipole moments are given for ground, excited states and transition states.
The chloromethane cation and dication have been studied using the complete active space self-cons... more The chloromethane cation and dication have been studied using the complete active space self-consistent field method followed by a multireference perturbative configuration interaction. The 2E ground state of CH3Cl presents a weak Jahn–Teller distortion, the 2A’ and 2A” components being separated by only 3.4 kcal/mol with very similar geometries. Both states are equilibrium structures. Contrary to previous calculations, the lowest singlet and triplet states of CH3Cl++ are calculated to be stable. While the 3A2 state keeps the neutral C3v symmetry, the 1E singlet state shows a large Jahn–Teller effect, with a splitting of 32.7 kcal/mol in favor of the 1A’ state, which is the ground state of the molecule. The planar 1A’ state of CH2Cl++ is found to be the most stable isomer, lying 41.4 kcal/mol below the corresponding state of CH3Cl++. The 3A” state, which lies 22.59 kcal/mol above the 1A’ state, has a nonplanar Cs-symmetry geometry. Finally, the CH3Cl++ (1A’) → CH2ClH++ (1A’) isomeri...
Université Lille 1 Sciences et Technologies Mémoire pour obtenir l'Habilitation à Diriger des Rec... more Université Lille 1 Sciences et Technologies Mémoire pour obtenir l'Habilitation à Diriger des Recherches Présenté par Denis DUFLOT Étude ab initio de molécules en phase gazeuse : double ionisation, spectroscopies en couches de valence et de coeur Soutenue publiquement le 11 juin 2009 devant le jury composé de :
We report on the first measurements of the electron impact electronic excitation cross sections f... more We report on the first measurements of the electron impact electronic excitation cross sections for C(4)F(6) isomers, hexafluoro-1,3-butadiene (1,3-C(4)F(6)), hexafluorocyclobutene (c-C(4)F(6)), and hexafluoro-2-butyne (2-C(4)F(6)), measured at 100 eV, 3° scattering angle, while sweeping the energy loss over the range 2.0-15.0 eV. Under these experimental conditions, optically allowed transitions are favored. The electronic state spectroscopy has been investigated and the assignments supported by quantum chemical calculations. The n = 3 members of the Rydberg series have been assigned converging to the lowest ionization energy limits of the C(4)F(6) isomers and classified according to the magnitude of the quantum defects (δ).
ABSTRACT We present high resolution VUV photoabsorption spectra of 1,4-pentadiene, C(5)H(8), over... more 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).
Inner-shell excitation spectra of gaseous monocyanoethylene, trans-dicyanoethylene, and allylcyan... more Inner-shell excitation spectra of gaseous monocyanoethylene, trans-dicyanoethylene, and allylcyanide have been measured at C1s and N1s edges using 2 keV electron collisions in quasi-dipolar excitation conditions and the electron energy loss spectroscopy. The energy resolution has allowed the observation of transitions from different carbon sites. Ab initio calculations have been made to help the assignment of the experimental features. The
The adsorption of a series of atoms and small molecules and radicals (H, C, N, O, NH, OH, H2O, CH... more The adsorption of a series of atoms and small molecules and radicals (H, C, N, O, NH, OH, H2O, CH3, and NH3) on hexagonal crystalline and amorphous ice clusters were obtained via classical molecular dynamics and electronic structure methods. The geometry and binding energies were calculated using a QMHigh:QMLow hybrid method on model clusters. Several combination of basis sets, density functionals and semi-empirical methods were compared and tested against previous works. More accurate binding energies were also refined via single point Coupled Cluster calculations. Most species, except carbon atom, physisorb on the surface, leading to rather small binding energies. The carbon atom forms a COH2 molecule and in some cases leads to the formation of a COH-H3O+ complex. Amorphous ices are characterized by slightly stronger binding energies than the crystalline phase. A major result of this work is to also access the dispersion of the binding energies since a variety of adsorption sites ...
The emission and use of synchrotron radiation (SR) are powerful tools for performing state-of-the... more The emission and use of synchrotron radiation (SR) are powerful tools for performing state-of-the art research at the fundamental and applied levels, benefiting a diversity of research areas across medicine, molecular and cell biology, condensed matter physics, nanotechnology, cultural heritage, environmental science, atomic and molecular physics, among many others.
Electronic state spectroscopy of CH3COOH has been investigated using Vacuum UltraViolet (VUV) pho... more Electronic state spectroscopy of CH3COOH has been investigated using Vacuum UltraViolet (VUV) photo-absorption spectroscopy in the energy range 3.5–10.6eV. The availability of a high-resolution photon beam (∼0.075nm) has allowed 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 10–14eV region have been studied
The journal of physical chemistry letters, Jan 5, 2017
Photoionization of a buckminsterfullerene ion is investigated using an ion trap and a merged beam... more Photoionization of a buckminsterfullerene ion is investigated using an ion trap and a merged beam setup coupled to synchrotron radiation beamlines and compared to theoretical calculations. Absolute measurements derived from the ion trap experiment allow discrepancies concerning the photoionization cross section of C60(+) to be solved.
The journal of physical chemistry. A, Jan 26, 2016
Electron energy loss (EEL) spectra of GeF4 have been measured with incident electrons at 100 eV f... more Electron energy loss (EEL) spectra of GeF4 have been measured with incident electrons at 100 eV for 5° scattering angle and at 30 eV for 30° scattering angle, while sweeping the energy loss over the range 7.0-21.0 eV. Low-lying excited triplet, singlet, valence and Rydberg states are investigated and the assignments supported by quantum chemical ab initio calculations. This provides the first comprehensive investigation of all singlet and triplet excited electronic states of germanium tetrafluoride up to the first ionisation energy. The Rydberg series converging to the (lowest) ionisation energy limits of GeF4 are also identified according to the magnitude of the quantum defects (δ).
To be published in the Journal of Chemical Physics The C2H photodissociation processes have been ... more To be published in the Journal of Chemical Physics The C2H photodissociation processes have been studied using ab initio multireference perturbative Configuration Interaction (Cl) methods. The calculated structural parameters of the two linear lowest lying states X2l:+ and A2TI were found to be in good agreement with previous theoretical and experimental works.' Construction of the correlation diagram indicates that C2H cannot photodissociate into C + CH. Therefore, two-dimensional potential energy surfaces of the six lowest lying A' and A" doublet states have been calculated as functions of the bond angle and the C-H bond distance, keeping the CC distance at the equilibrium C2H value. It appears that the 1 2A', 2 2A' and 1 2A" states correlating to the X2l:,+ and A2TI states in linear geometry remain bound at ail angles, whereas the 3 2A', 4 2A' and 4 2A" are dissociative. However, the structure of the energy surfaces is complicated by the presence of numerous avoided crossings between these states. Transition dipole moments connecting the excited states with the X2l:,+ and A2TI states have been also obtained in linear geometry. They were calculated to be very weak, leading JO the conclusion that the photodissociation rate of C2H will be negligeable below 7 eV. Higher lying states, including Rydberg states, were not considered here, since they cannot dissociate direct! y into C2 + H.
Ab initio electronic structure theory (MCSCF+CI) has been used to determine the more important fe... more Ab initio electronic structure theory (MCSCF+CI) has been used to determine the more important features of the potential energy surface for the simple isomerization reaction HCSi ↠ HSiC.Our preliminary results indicate that H-Si-C has a bent structure while H-C-Si is linear. More, the H-Si-C ground state is 2A’ and it is 2&Pgr; for H-C-Si.Potential barriers for isomerization are calculated. Geometries, energies and dipole moments are given for ground, excited states and transition states.
The chloromethane cation and dication have been studied using the complete active space self-cons... more The chloromethane cation and dication have been studied using the complete active space self-consistent field method followed by a multireference perturbative configuration interaction. The 2E ground state of CH3Cl presents a weak Jahn–Teller distortion, the 2A’ and 2A” components being separated by only 3.4 kcal/mol with very similar geometries. Both states are equilibrium structures. Contrary to previous calculations, the lowest singlet and triplet states of CH3Cl++ are calculated to be stable. While the 3A2 state keeps the neutral C3v symmetry, the 1E singlet state shows a large Jahn–Teller effect, with a splitting of 32.7 kcal/mol in favor of the 1A’ state, which is the ground state of the molecule. The planar 1A’ state of CH2Cl++ is found to be the most stable isomer, lying 41.4 kcal/mol below the corresponding state of CH3Cl++. The 3A” state, which lies 22.59 kcal/mol above the 1A’ state, has a nonplanar Cs-symmetry geometry. Finally, the CH3Cl++ (1A’) → CH2ClH++ (1A’) isomeri...
Université Lille 1 Sciences et Technologies Mémoire pour obtenir l'Habilitation à Diriger des Rec... more Université Lille 1 Sciences et Technologies Mémoire pour obtenir l'Habilitation à Diriger des Recherches Présenté par Denis DUFLOT Étude ab initio de molécules en phase gazeuse : double ionisation, spectroscopies en couches de valence et de coeur Soutenue publiquement le 11 juin 2009 devant le jury composé de :
We report on the first measurements of the electron impact electronic excitation cross sections f... more We report on the first measurements of the electron impact electronic excitation cross sections for C(4)F(6) isomers, hexafluoro-1,3-butadiene (1,3-C(4)F(6)), hexafluorocyclobutene (c-C(4)F(6)), and hexafluoro-2-butyne (2-C(4)F(6)), measured at 100 eV, 3° scattering angle, while sweeping the energy loss over the range 2.0-15.0 eV. Under these experimental conditions, optically allowed transitions are favored. The electronic state spectroscopy has been investigated and the assignments supported by quantum chemical calculations. The n = 3 members of the Rydberg series have been assigned converging to the lowest ionization energy limits of the C(4)F(6) isomers and classified according to the magnitude of the quantum defects (δ).
ABSTRACT We present high resolution VUV photoabsorption spectra of 1,4-pentadiene, C(5)H(8), over... more 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).
Inner-shell excitation spectra of gaseous monocyanoethylene, trans-dicyanoethylene, and allylcyan... more Inner-shell excitation spectra of gaseous monocyanoethylene, trans-dicyanoethylene, and allylcyanide have been measured at C1s and N1s edges using 2 keV electron collisions in quasi-dipolar excitation conditions and the electron energy loss spectroscopy. The energy resolution has allowed the observation of transitions from different carbon sites. Ab initio calculations have been made to help the assignment of the experimental features. The
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