The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Martí Rosés - One of the best experts on this subject based on the ideXlab platform.
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autoprotolysis in aqueous organic solvent mixtures water alcohol binary systems
Analytica Chimica Acta, 1996Co-Authors: G. Fonrodona, Elisabeth Bosch, Clara Ràfols, Martí RosésAbstract:By use of a previously derived equation, the main factors that contribute to autoprotolysis are studied for different water/ alcohol mixtures. These factors are: Autoionization of water, Autoionization of the alcohol, and proton transfer from water to the alcohol or from the alcohol to water. The most important factors seem to be the proton transfer from the alcohol to water, and to a much lesser degree, the Autoionization of water. The Autoionization of the alcohol is only significant for pure alcohol. The different factors have been correlated with the solvent properties polarity and hydrogen-bond ability. An increase in these solvent properties favours Autoionization and proton transfer, and therefore decreases the observed autoprotolysis pK value. The proposed equation and the parameters calculated allow an accurate estimation of the autoprotolysis pK value for any studied water/alcohol system.
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Autoprotolysis in aqueous organic solvent mixtures.Water/alcohol binary systems
Analytica Chimica Acta, 1996Co-Authors: G. Fonrodona, Elisabeth Bosch, Clara Ràfols, Martí RosésAbstract:By use of a previously derived equation, the main factors that contribute to autoprotolysis are studied for different water/ alcohol mixtures. These factors are: Autoionization of water, Autoionization of the alcohol, and proton transfer from water to the alcohol or from the alcohol to water. The most important factors seem to be the proton transfer from the alcohol to water, and to a much lesser degree, the Autoionization of water. The Autoionization of the alcohol is only significant for pure alcohol. The different factors have been correlated with the solvent properties polarity and hydrogen-bond ability. An increase in these solvent properties favours Autoionization and proton transfer, and therefore decreases the observed autoprotolysis pK value. The proposed equation and the parameters calculated allow an accurate estimation of the autoprotolysis pK value for any studied water/alcohol system.
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Autoprotolysis in aqueous organic solvent mixtures. Water-amide and water-amine binary systems
Analytica Chimica Acta, 1995Co-Authors: Clara Ràfols, Elisabeth Bosch, Martí Rosés, Agustin G. AsueroAbstract:Abstract The contribution of the Autoionization of water and organic solvent, and the proton transfer between them to the overall autoprotolysis of mixtures of water with amides ( N , N -dimethylacetamide, N -methylacetamide, acetamide, N , N -dimethylformamide, N -methylformamide and formamide) and with amines (butylamine, N , N -diethylaminoethanol and ethanolamine) is studied and compared. Proton transfer from water to the more basic amide, and specially amine, produces the autoprotolysis in the intermediate solvent compositions and predominates over a wide range of solvent compositions. Autoionization of water predominates only for very low amide or amine contents. Autoionization of the amide or the amine can be important at intermediate and high organic solvent compositions if the pure amide or amine has a high autoprotolysis constant (p K ap value lower than that of pure water). Because of the higher basicity of amines over amides, proton transfer from water to the amine produces very high autoprotolysis constants for water-amine mixtures.
S. T. Pratt - One of the best experts on this subject based on the ideXlab platform.
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Mode dependent vibrational Autoionization of Rydberg states of NO2. II. Comparing the symmetric stretching and bending vibrations.
The Journal of chemical physics, 2004Co-Authors: Patrice Bell, F. Aguirre, Edward R. Grant, S. T. PrattAbstract:Triple-resonance excitation and high-resolution photoelectron spectroscopy are combined to characterize the mode selectivity of vibrational Autoionization of the high Rydberg states of NO2. Photoelectron spectra and vibrational branching fractions are reported for autoionizing Rydberg states converging to the NO2+ X 1Sigmag +(110) state, that is, with one quantum in the symmetric stretch, nu1, and one quantum in the bending vibration, nu2. These results indicate that Autoionization proceeds most efficiently through the loss of one quantum from the symmetric stretch rather than from the bending vibration. The implications of this result are discussed in terms of the Autoionization mechanism.
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Mode-dependent vibrational Autoionization of NO2
The Journal of Chemical Physics, 2003Co-Authors: Patrice Bell, F. Aguirre, Edward R. Grant, S. T. PrattAbstract:Triple-resonance excitation and high-resolution photoelectron spectroscopy were combined to study the mode dependence of vibrational Autoionization in Rydberg states of NO2. Photoselection isolates vibrational Autoionization via the symmetric stretching vibration, ν1, and the bending vibration, ν2. The previously characterized Fermi resonance between one quantum of ν1 and two quanta of ν2 [H. Matsui et al., J. Mol. Spectrosc. 175, 203 (1996)] allows the comparison of the vibrational Autoionization matrix elements for these two modes. The squared matrix element for vibrational Autoionization via the symmetric stretch is found to be approximately 35 times greater than that for the bend, which is also consistent with previous results. The results are discussed in terms of existing theoretical models for the Autoionization process.
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Mode-dependent vibrational Autoionization in aniline
The Journal of Chemical Physics, 2000Co-Authors: C. A. Raptis, S. T. PrattAbstract:High-resolution photoelectron spectroscopy is used to study the branching ratios for vibrational Autoionization of Rydberg states of aniline (C6H5NH2) converging to the ground electronic state of the ion. By using two-color double-resonance excitation, it is possible to prepare autoionizing resonances in which two different vibrational modes are excited. Determination of the vibrational state distribution in the product ion provides information on the relative rates of Autoionization for the two modes. It is found that some normal modes appear to be especially effective at promoting vibrational Autoionization, while others appear to be completely ineffective.
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Photoelectron spectroscopy of ammonia : mode-dependent vibrational Autoionization.
The Journal of Chemical Physics, 2000Co-Authors: J. A. Bacon, S. T. PrattAbstract:Photoelectron spectroscopy was used to study the mode dependence of vibrational Autoionization in high-Rydberg states of NH3. Two-color, two-photon resonant, three-photon excitation via the C′ 1A1′(1300) intermediate state was used to populate selected autoionizing Rydberg states between the (1200) and (1300) ionization thresholds of the NH3+ X 2A2″ ground electronic state, and the ionic vibrational distributions were determined from the photoelectron spectra. Excitation of Rydberg states in which two different vibrational modes are excited allowed the direct comparison of the Autoionization efficiencies for the two modes. Autoionization via the loss of one quantum of vibrational energy from the nontotally symmetric “umbrella” mode, ν2, was found to be the dominant Autoionization process. Vibrational branching fractions obtained from the ionic vibrational distributions indicate that, for the Rydberg states accessed via the C′ 1A1′(1300) intermediate state, the ν2 mode is approximately 25 times more eff...
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Photoelectron spectroscopy of autoionizing Rydberg states of ammonia
The Journal of Chemical Physics, 2000Co-Authors: J. A. Bacon, S. T. PrattAbstract:Photoelectron spectroscopy was used to determine the ionic vibrational distributions following vibrational Autoionization of Rydberg states of NH3. Two-color, two-photon resonant, three-photon excitation via selected rotational levels of the NH3 C′ 1A1′(0200) intermediate state was employed to populate vibrationally autoionizing Rydberg states between the v2+=1 and v2+=2 ionization thresholds of the NH3+ X 2A2″ ground electronic state. As expected from the propensity rule for vibrational Autoionization, ionization with Δv2=−1 was found to be the dominant process. The observed vibrational distributions appear to be independent of the rotational quantum number of the autoionizing state. Partially resolved rotational structure was exhibited within the photoelectron spectra providing information on the assignments of the Rydberg states and on the mechanism for vibrational Autoionization.
C. L. Arnold - One of the best experts on this subject based on the ideXlab platform.
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Spectral phase measurement of a Fano resonance using tunable attosecond pulses
Nature Communications, 2016Co-Authors: M. Kotur, D. Guénot, Á Jiménez-galán, D. Kroon, E. W. Larsen, M. Louisy, S. Bengtsson, M. Miranda, J. Mauritsson, C. L. ArnoldAbstract:Electron dynamics induced by resonant absorption of light is of fundamental importance in nature and has been the subject of countless studies in many scientific areas. Above the ionization threshold of atomic or molecular systems, the presence of discrete states leads to Autoionization, which is an interference between two quantum paths: direct ionization and excitation of the discrete state coupled to the continuum. Traditionally studied with synchrotron radiation, the probability for Autoionization exhibits a universal Fano intensity profile as a function of excitation energy. However, without additional phase information, the full temporal dynamics cannot be recovered. Here we use tunable attosecond pulses combined with weak infrared radiation in an interferometric setup to measure not only the intensity but also the phase variation of the photoionization amplitude across an Autoionization resonance in argon. The phase variation can be used as a fingerprint of the interactions between the discrete state and the ionization continua, indicating a new route towards monitoring electron correlations in time. Resonant absorption of light in atoms can lead to Autoionization, whose probability exhibits a Fano intensity profile. Here, the authors use attosecond pulses and weak infrared radiation to study the phase variation of the photoionization amplitude across an Autoionization resonance in argon.
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Spectral phase measurement of a Fano resonance using tunable attosecond pulses
Nature Communications, 2016Co-Authors: M. Kotur, D. Guénot, Á Jiménez-galán, D. Kroon, E. W. Larsen, M. Louisy, S. Bengtsson, M. Miranda, J. Mauritsson, C. L. ArnoldAbstract:Electron dynamics induced by resonant absorption of light is of fundamental importance in nature and has been the subject of countless studies in many scientific areas. Above the ionization threshold of atomic or molecular systems, the presence of discrete states leads to Autoionization, which is an interference between two quantum paths: direct ionization and excitation of the discrete state coupled to the continuum. Traditionally studied with synchrotron radiation, the probability for Autoionization exhibits a universal Fano intensity profile as a function of excitation energy. However, without additional phase information, the full temporal dynamics cannot be recovered. Here we use tunable attosecond pulses combined with weak infrared radiation in an interferometric setup to measure not only the intensity but also the phase variation of the photoionization amplitude across an Autoionization resonance in argon. The phase variation can be used as a fingerprint of the interactions between the discrete state and the ionization continua, indicating a new route towards monitoring electron correlations in time.
Clara Ràfols - One of the best experts on this subject based on the ideXlab platform.
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autoprotolysis in aqueous organic solvent mixtures water alcohol binary systems
Analytica Chimica Acta, 1996Co-Authors: G. Fonrodona, Elisabeth Bosch, Clara Ràfols, Martí RosésAbstract:By use of a previously derived equation, the main factors that contribute to autoprotolysis are studied for different water/ alcohol mixtures. These factors are: Autoionization of water, Autoionization of the alcohol, and proton transfer from water to the alcohol or from the alcohol to water. The most important factors seem to be the proton transfer from the alcohol to water, and to a much lesser degree, the Autoionization of water. The Autoionization of the alcohol is only significant for pure alcohol. The different factors have been correlated with the solvent properties polarity and hydrogen-bond ability. An increase in these solvent properties favours Autoionization and proton transfer, and therefore decreases the observed autoprotolysis pK value. The proposed equation and the parameters calculated allow an accurate estimation of the autoprotolysis pK value for any studied water/alcohol system.
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Autoprotolysis in aqueous organic solvent mixtures.Water/alcohol binary systems
Analytica Chimica Acta, 1996Co-Authors: G. Fonrodona, Elisabeth Bosch, Clara Ràfols, Martí RosésAbstract:By use of a previously derived equation, the main factors that contribute to autoprotolysis are studied for different water/ alcohol mixtures. These factors are: Autoionization of water, Autoionization of the alcohol, and proton transfer from water to the alcohol or from the alcohol to water. The most important factors seem to be the proton transfer from the alcohol to water, and to a much lesser degree, the Autoionization of water. The Autoionization of the alcohol is only significant for pure alcohol. The different factors have been correlated with the solvent properties polarity and hydrogen-bond ability. An increase in these solvent properties favours Autoionization and proton transfer, and therefore decreases the observed autoprotolysis pK value. The proposed equation and the parameters calculated allow an accurate estimation of the autoprotolysis pK value for any studied water/alcohol system.
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Autoprotolysis in aqueous organic solvent mixtures. Water-amide and water-amine binary systems
Analytica Chimica Acta, 1995Co-Authors: Clara Ràfols, Elisabeth Bosch, Martí Rosés, Agustin G. AsueroAbstract:Abstract The contribution of the Autoionization of water and organic solvent, and the proton transfer between them to the overall autoprotolysis of mixtures of water with amides ( N , N -dimethylacetamide, N -methylacetamide, acetamide, N , N -dimethylformamide, N -methylformamide and formamide) and with amines (butylamine, N , N -diethylaminoethanol and ethanolamine) is studied and compared. Proton transfer from water to the more basic amide, and specially amine, produces the autoprotolysis in the intermediate solvent compositions and predominates over a wide range of solvent compositions. Autoionization of water predominates only for very low amide or amine contents. Autoionization of the amide or the amine can be important at intermediate and high organic solvent compositions if the pure amide or amine has a high autoprotolysis constant (p K ap value lower than that of pure water). Because of the higher basicity of amines over amides, proton transfer from water to the amine produces very high autoprotolysis constants for water-amine mixtures.
Elisabeth Bosch - One of the best experts on this subject based on the ideXlab platform.
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autoprotolysis in aqueous organic solvent mixtures water alcohol binary systems
Analytica Chimica Acta, 1996Co-Authors: G. Fonrodona, Elisabeth Bosch, Clara Ràfols, Martí RosésAbstract:By use of a previously derived equation, the main factors that contribute to autoprotolysis are studied for different water/ alcohol mixtures. These factors are: Autoionization of water, Autoionization of the alcohol, and proton transfer from water to the alcohol or from the alcohol to water. The most important factors seem to be the proton transfer from the alcohol to water, and to a much lesser degree, the Autoionization of water. The Autoionization of the alcohol is only significant for pure alcohol. The different factors have been correlated with the solvent properties polarity and hydrogen-bond ability. An increase in these solvent properties favours Autoionization and proton transfer, and therefore decreases the observed autoprotolysis pK value. The proposed equation and the parameters calculated allow an accurate estimation of the autoprotolysis pK value for any studied water/alcohol system.
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Autoprotolysis in aqueous organic solvent mixtures.Water/alcohol binary systems
Analytica Chimica Acta, 1996Co-Authors: G. Fonrodona, Elisabeth Bosch, Clara Ràfols, Martí RosésAbstract:By use of a previously derived equation, the main factors that contribute to autoprotolysis are studied for different water/ alcohol mixtures. These factors are: Autoionization of water, Autoionization of the alcohol, and proton transfer from water to the alcohol or from the alcohol to water. The most important factors seem to be the proton transfer from the alcohol to water, and to a much lesser degree, the Autoionization of water. The Autoionization of the alcohol is only significant for pure alcohol. The different factors have been correlated with the solvent properties polarity and hydrogen-bond ability. An increase in these solvent properties favours Autoionization and proton transfer, and therefore decreases the observed autoprotolysis pK value. The proposed equation and the parameters calculated allow an accurate estimation of the autoprotolysis pK value for any studied water/alcohol system.
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Autoprotolysis in aqueous organic solvent mixtures. Water-amide and water-amine binary systems
Analytica Chimica Acta, 1995Co-Authors: Clara Ràfols, Elisabeth Bosch, Martí Rosés, Agustin G. AsueroAbstract:Abstract The contribution of the Autoionization of water and organic solvent, and the proton transfer between them to the overall autoprotolysis of mixtures of water with amides ( N , N -dimethylacetamide, N -methylacetamide, acetamide, N , N -dimethylformamide, N -methylformamide and formamide) and with amines (butylamine, N , N -diethylaminoethanol and ethanolamine) is studied and compared. Proton transfer from water to the more basic amide, and specially amine, produces the autoprotolysis in the intermediate solvent compositions and predominates over a wide range of solvent compositions. Autoionization of water predominates only for very low amide or amine contents. Autoionization of the amide or the amine can be important at intermediate and high organic solvent compositions if the pure amide or amine has a high autoprotolysis constant (p K ap value lower than that of pure water). Because of the higher basicity of amines over amides, proton transfer from water to the amine produces very high autoprotolysis constants for water-amine mixtures.
