The effects of an anti-hydrogen bond on the v1 v12 Fermi resonance （FR） of pyridine are experimentally investigated by using Raman scattering spectroscopy. Three systems, pyridine/water, pyridine/formamide, and pyri...The effects of an anti-hydrogen bond on the v1 v12 Fermi resonance （FR） of pyridine are experimentally investigated by using Raman scattering spectroscopy. Three systems, pyridine/water, pyridine/formamide, and pyridine/carbon tetrachloride, provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex. Water forms a stronger anti-hydrogen bond with pyridine than with formamide, and in the case of adding non-polar solvent carbon tetrachloride, which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine, the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce. The dilution studies are performed on the three systems. Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode v1 and triangle mode v12 of pyridine at different volume concentrations, which are calculated according to the Bertran equations, in three systems, we find that the solution with the strongest anti-hydrogen bond, water, shows the fastest change in the v1-v12 Fermi coupling coefficient W with the volume concentration varying, followed by the formamide and carbon tetrachloride solutions. These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the v1-v12 FR of pyridine. According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory, a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the v1 - v12 FR of pyridine is given.展开更多
The Fermi resonance behaviours of the two groups of binary solutions -- pyridine and methanol, benzene and carbon tetrachloride, under different pressures are investigated according to their Raman spectra. The effect ...The Fermi resonance behaviours of the two groups of binary solutions -- pyridine and methanol, benzene and carbon tetrachloride, under different pressures are investigated according to their Raman spectra. The effect of pressure on Fermi resonance in binary solution differs significantly from that in pure liquid. In a binary solution, with the intermolecular distance shortening, the intermolecular interaction potential increases, the shift rates of the Raman spectral lines increase, the spectral line splitting occurs ahead of that in pure liquid, and the wavenumber separation A0 between the unperturbed harmonic levels shifts more quickly, too. The Fermi resonance parameters, the coupling coefficient W and the intensity ratio R of the two Raman bands, decrease rapidly with pressure increasing, and the pressure at which Fermi resonance phenomenon disappears is much lower than that in pure liquid, especially in the solution whose molecules are of the same polarity. This article is valuable in the identification and the assignment of spectral lines under high pressure, as well as the study of high pressure effect, intermolecular interaction, and solvent effects in different cases, etc.展开更多
An algebraic Harniltonian for the two coupled nonlinear vibrations of highly excited nonrigid molecule HCP was presented. The Hamiltonian reduces to the conventional one in a limit which was expressed in terms of harm...An algebraic Harniltonian for the two coupled nonlinear vibrations of highly excited nonrigid molecule HCP was presented. The Hamiltonian reduces to the conventional one in a limit which was expressed in terms of harmonic oscillator operators. It showed that the algebraic model can better reproduce the data than the conventional model by fitting the observed data of HCP.展开更多
The mode selectivity of the H+CH_(3)D→H_(2)+CH_(2)D reaction was studied using a recently developed ten-dimensional time-dependent wave packet method.The reaction dynamics are studied for the reactant CH_(3)D initial...The mode selectivity of the H+CH_(3)D→H_(2)+CH_(2)D reaction was studied using a recently developed ten-dimensional time-dependent wave packet method.The reaction dynamics are studied for the reactant CH_(3)D initially from the ground state,the CH_(3) symmetry and asymmetry stretching excitation,the CD stretching excitation and the fundamental and the first overtone of the CH_(3) bending mode.The calculated reaction probabilities show that exciting either of the CH_(3) stretching modes enhances the reactivity in the collision energy range below 1.0 eV,while the CD stretching excitation does not obviously prompt the reaction.Fundamental CH_(3) bending excitation has nearly no effect on promoting reactivity.However,a significant enhancement is observed for the first overtone excitation of the CH_(3) bending mode,resulting from the Fermi resonance between the fundamental state of the CH_(3) symmetry stretching mode and the first overtone state of the CH_(3) bending mode.展开更多
Infrared absorption spectra of gaseous CH2Cl2 in the regions of 1200-12000 cm^-1 were measured using a Bruker IFS 120HR Fourier transform spectrometer in conjunction with a nmltipass cell. 47 vibrational levels of ove...Infrared absorption spectra of gaseous CH2Cl2 in the regions of 1200-12000 cm^-1 were measured using a Bruker IFS 120HR Fourier transform spectrometer in conjunction with a nmltipass cell. 47 vibrational levels of overtone and combinational spectral lines of the CH stretching （v1, v6）, bending （v2）, and rocking （v8） modes were analyzed and assigned. Utilizing the normal mode model and considering the coupling among CH stretching, bending and rocking vibrations, values of the harmonic frequency wi, the anharmonic constant xij, and the coefficients of Fermi and the Darling-Dennison resonances of v1, v6, v2 and v8 modes were also determined from experimental spectral data with nonlinear least-square fitting. These spectral constants reproduced the experimental levels very well. These results showed that Fermi resonance between CH stretching and rocking vibrations （kiss=-254.63 cm^-1） is stronger than that between CH stretching and bending vibrations （k122 = 54.87 cm^-1 ）; and that Darling-Dennison resonances between CH stretching and bending vibrations （k166=-215.28 cm^-1） is also much stronger than that between CH bending and rocking vibrations （k2288=5.72 cm^-1）.展开更多
Internal vibrations underlie transient structure formation,spectroscopy,and dynamics.However,at least two challenges exist when aiming to elucidate the contributions of vibrational motions on the potential energy surf...Internal vibrations underlie transient structure formation,spectroscopy,and dynamics.However,at least two challenges exist when aiming to elucidate the contributions of vibrational motions on the potential energy surfaces.One is the acquisition of well-resolved experimental infrared spectra,and the other is the development of efficient theoretical methodologies that reliably predict band positions,relative intensities,and substructures.Here,we report size-specific infrared spectra of ammonia clusters to address these two challenges.Unprecedented agreement between experiment and state-of-the-art quantum simulations reveals that the vibrational spectra are mainly contributed by proton-donor ammonia.A striking Fermi resonance observed at approximately 3210 and 3250 cm^(−1)originates from the coupling of NH symmetric stretch fundamentals with overtones of free and hydrogen-bonded NH bending,respectively.These novel,intriguing findings contribute to a better understanding of vibrational motions in a large variety of hydrogen-bonded complexes with orders of magnitude improvements in spectral resolution,efficiency,and specificity.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No. 10974067） and the Graduate Innovation Fund of Jilin University, China （Grant No. 20101055）.
文摘The effects of an anti-hydrogen bond on the v1 v12 Fermi resonance （FR） of pyridine are experimentally investigated by using Raman scattering spectroscopy. Three systems, pyridine/water, pyridine/formamide, and pyridine/carbon tetrachloride, provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex. Water forms a stronger anti-hydrogen bond with pyridine than with formamide, and in the case of adding non-polar solvent carbon tetrachloride, which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine, the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce. The dilution studies are performed on the three systems. Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode v1 and triangle mode v12 of pyridine at different volume concentrations, which are calculated according to the Bertran equations, in three systems, we find that the solution with the strongest anti-hydrogen bond, water, shows the fastest change in the v1-v12 Fermi coupling coefficient W with the volume concentration varying, followed by the formamide and carbon tetrachloride solutions. These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the v1-v12 FR of pyridine. According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory, a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the v1 - v12 FR of pyridine is given.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10774057 and 10974067)
文摘The Fermi resonance behaviours of the two groups of binary solutions -- pyridine and methanol, benzene and carbon tetrachloride, under different pressures are investigated according to their Raman spectra. The effect of pressure on Fermi resonance in binary solution differs significantly from that in pure liquid. In a binary solution, with the intermolecular distance shortening, the intermolecular interaction potential increases, the shift rates of the Raman spectral lines increase, the spectral line splitting occurs ahead of that in pure liquid, and the wavenumber separation A0 between the unperturbed harmonic levels shifts more quickly, too. The Fermi resonance parameters, the coupling coefficient W and the intensity ratio R of the two Raman bands, decrease rapidly with pressure increasing, and the pressure at which Fermi resonance phenomenon disappears is much lower than that in pure liquid, especially in the solution whose molecules are of the same polarity. This article is valuable in the identification and the assignment of spectral lines under high pressure, as well as the study of high pressure effect, intermolecular interaction, and solvent effects in different cases, etc.
文摘An algebraic Harniltonian for the two coupled nonlinear vibrations of highly excited nonrigid molecule HCP was presented. The Hamiltonian reduces to the conventional one in a limit which was expressed in terms of harmonic oscillator operators. It showed that the algebraic model can better reproduce the data than the conventional model by fitting the observed data of HCP.
基金supported by the National Natural Science Foundation of China(No.21773297,No.21973108,and No.21921004 to Minghui Yang,No.21973109 to Hongwei Song)。
文摘The mode selectivity of the H+CH_(3)D→H_(2)+CH_(2)D reaction was studied using a recently developed ten-dimensional time-dependent wave packet method.The reaction dynamics are studied for the reactant CH_(3)D initially from the ground state,the CH_(3) symmetry and asymmetry stretching excitation,the CD stretching excitation and the fundamental and the first overtone of the CH_(3) bending mode.The calculated reaction probabilities show that exciting either of the CH_(3) stretching modes enhances the reactivity in the collision energy range below 1.0 eV,while the CD stretching excitation does not obviously prompt the reaction.Fundamental CH_(3) bending excitation has nearly no effect on promoting reactivity.However,a significant enhancement is observed for the first overtone excitation of the CH_(3) bending mode,resulting from the Fermi resonance between the fundamental state of the CH_(3) symmetry stretching mode and the first overtone state of the CH_(3) bending mode.
基金This work was supported by National Natural Science Foundation of China （Grant No. 10274077, 20103007 and 29703007）. The authors would like to thank Wei Chu, Yong-qiang Xu and Guo-sheng Cheng for their kind help.
文摘Infrared absorption spectra of gaseous CH2Cl2 in the regions of 1200-12000 cm^-1 were measured using a Bruker IFS 120HR Fourier transform spectrometer in conjunction with a nmltipass cell. 47 vibrational levels of overtone and combinational spectral lines of the CH stretching （v1, v6）, bending （v2）, and rocking （v8） modes were analyzed and assigned. Utilizing the normal mode model and considering the coupling among CH stretching, bending and rocking vibrations, values of the harmonic frequency wi, the anharmonic constant xij, and the coefficients of Fermi and the Darling-Dennison resonances of v1, v6, v2 and v8 modes were also determined from experimental spectral data with nonlinear least-square fitting. These spectral constants reproduced the experimental levels very well. These results showed that Fermi resonance between CH stretching and rocking vibrations （kiss=-254.63 cm^-1） is stronger than that between CH stretching and bending vibrations （k122 = 54.87 cm^-1 ）; and that Darling-Dennison resonances between CH stretching and bending vibrations （k166=-215.28 cm^-1） is also much stronger than that between CH bending and rocking vibrations （k2288=5.72 cm^-1）.
基金supported by the National Natural Science Foundation of China(grant nos.21673231 and 21688102)the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(grant no.XDB17000000)+3 种基金the Dalian Institute of Chemical Physics(DICP DCLS201702)K.C.Wong Education Foundation(GJTD-2018-06)supported by the Ministry of Science and Technology of Taiwan(MOST-106-2811-M-001-051 and MOST-107-2628-M-001-002-MY4)the Academia Sinica.
文摘Internal vibrations underlie transient structure formation,spectroscopy,and dynamics.However,at least two challenges exist when aiming to elucidate the contributions of vibrational motions on the potential energy surfaces.One is the acquisition of well-resolved experimental infrared spectra,and the other is the development of efficient theoretical methodologies that reliably predict band positions,relative intensities,and substructures.Here,we report size-specific infrared spectra of ammonia clusters to address these two challenges.Unprecedented agreement between experiment and state-of-the-art quantum simulations reveals that the vibrational spectra are mainly contributed by proton-donor ammonia.A striking Fermi resonance observed at approximately 3210 and 3250 cm^(−1)originates from the coupling of NH symmetric stretch fundamentals with overtones of free and hydrogen-bonded NH bending,respectively.These novel,intriguing findings contribute to a better understanding of vibrational motions in a large variety of hydrogen-bonded complexes with orders of magnitude improvements in spectral resolution,efficiency,and specificity.
