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Jianping Wang - One of the best experts on this subject based on the ideXlab platform.
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ultrafast Vibrational Energy Transfer through the covalent bond and intra and intermolecular hydrogen bonds in a supramolecular dimer by two dimensional infrared spectroscopy
Journal of Physical Chemistry B, 2020Co-Authors: Xueqian Dong, Pengyun Yu, Juan Zhao, Sumin Wang, Fan Yang, Lizhu Wu, Chenho Tung, Jianping WangAbstract:: In this work, the structural fluctuations and Vibrational Energy Transfer dynamics in a supramolecular homodimer model, which is composed of 2-(9-anthracene)ureido-6-(1-undecyl)-4[1H]-pyrimidinone (UPAn) with quadruple intermolecular and single intramolecular hydrogen bonds (HBs), have been examined using ultrafast two-dimensional infrared (2D IR) and steady-state IR spectroscopies. A less structurally fluctuating intermolecular HB is found between the pyrimidinone C═O and ureido N-H groups. However, a larger structurally fluctuating intramolecular HB is suggested by the equilibrium and dynamical line-shape measurements of the ureido C═O stretch. Further, dynamical time-dependent 2D IR diagonal and off-diagonal signals show that intra- and intermolecular Vibrational Energy Transfer processes occur on the picosecond timescale, where the latter is more efficient due to intermolecular hydrogen bonding interaction and through-space interaction.
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ultrafast intermolecular Vibrational Energy Transfer in hexahydro 1 3 5 trinitro 1 3 5 triazine in molecular crystal by 2d ir spectroscopy
Journal of Physical Chemistry C, 2020Co-Authors: Pengyun Yu, Juan Zhao, Jianping WangAbstract:Cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine (HHTT) is an important energetic molecule with a variety of applications. In this work, structural dynamics and Vibrational-Energy Transfer dynamics of HHTT were investigated using steady-state infrared (IR), femtosecond time-resolved IR, and two-dimensional (2D) IR spectroscopic methods. Two different structural forms of HHTT (isolated molecules dissolved in DMSO and microcrystal dispersed in paraffin oil) were examined using the NO2 asymmetric stretching mode as a structural marker. Both intra- and intermolecular Vibrational Energy Transfers were observed in HHTT microcrystal, where the well-known α-conformation was retained. However, less perfect α-HHTT species was found in DMSO. An intermolecular Energy dissipation pathway was found to be related to Davydov splitting in the microcrystal form of HHTT, which originates from intermolecular interactions (e.g., electrostatic and hydrogen bonds). Experimental results were supported by quantum-chemistry co...
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ultrafast intermolecular Vibrational Energy Transfer in hexahydro 1 3 5 trinitro 1 3 5 triazine in molecular crystal by 2d ir spectroscopy
Journal of Physical Chemistry C, 2020Co-Authors: Lu Shi, Juan Zhao, Jianping WangAbstract:Cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine (HHTT) is an important energetic molecule with a variety of applications. In this work, structural dynamics and Vibrational-Energy Transfer dyna...
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ultrafast intermolecular Vibrational Energy Transfer in hexahydro 1 3 5 trinitro 1 3 5 triazine in molecular crystal by 2d ir spectroscopy
The Journal of Physical Chemistry, 2020Co-Authors: Pengyun Yu, Juan Zhao, Jianping WangAbstract:Cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine (HHTT) is an important energetic molecule with a variety of applications. In this work, structural dynamics and Vibrational-Energy Transfer dynamics of HHTT were investigated using steady-state infrared (IR), femtosecond time-resolved IR, and two-dimensional (2D) IR spectroscopic methods. Two different structural forms of HHTT (isolated molecules dissolved in DMSO and microcrystal dispersed in paraffin oil) were examined using the NO₂ asymmetric stretching mode as a structural marker. Both intra- and intermolecular Vibrational Energy Transfers were observed in HHTT microcrystal, where the well-known α-conformation was retained. However, less perfect α-HHTT species was found in DMSO. An intermolecular Energy dissipation pathway was found to be related to Davydov splitting in the microcrystal form of HHTT, which originates from intermolecular interactions (e.g., electrostatic and hydrogen bonds). Experimental results were supported by quantum-chemistry computations. In addition, both Vibrational excited-state relaxation and Vibrational Energy-Transfer processes were found to be more efficient in HHTT microcrystal than in the solvated form. Our work provides a chemical-bond level of insight into the nitro group-containing energetic materials.
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ultrafast intramolecular Vibrational Energy Transfer in carbon nitride hydrocolloid examined by femtosecond two dimensional infrared spectroscopy
Journal of Chemical Physics, 2019Co-Authors: Xuan Zheng, Jianping WangAbstract:In this work, ultrafast Vibrational and structural processes in a graphitic carbon nitride hydrocolloid system were studied using a combination of linear infrared and nonlinear two-dimensional infrared (2D IR) spectroscopies. The experimentally observed three IR line shapes in the C=N stretching vibration frequency region were analyzed and attributed to the rigid and conjugated molecular frame of the prepared g-CN molecular species, which is believed to be a dimeric tris-s-triazine, as well as attributed to insignificant solvent influence on the delocalized C=N vibrations. Vibrational transition density cubes were also computed for the proposed g-CN dimer, confirming the heterocyclic C=N stretching nature of the three IR absorption peaks. Intramolecular Vibrational Energy Transfer dynamics and spectral diffusion of the g-CN system were characterized by examining a series of time-dependent 2D IR spectra. A picosecond intramolecular Vibrational Energy redistribution process was found to occur among these delocalized C=N stretching modes, acting as an efficient Vibrational Energy Transfer channel. This work reasonably connects the experimentally observed IR signature to a specific g-CN structure and also provides the first report on the ultrafast intramolecular processes of such carbon nitride systems. The obtained results are fundamentally important for understanding the molecular mechanisms of such carbon-nitride based functional materials.
Pengyun Yu - One of the best experts on this subject based on the ideXlab platform.
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ultrafast Vibrational Energy Transfer through the covalent bond and intra and intermolecular hydrogen bonds in a supramolecular dimer by two dimensional infrared spectroscopy
Journal of Physical Chemistry B, 2020Co-Authors: Xueqian Dong, Pengyun Yu, Juan Zhao, Sumin Wang, Fan Yang, Lizhu Wu, Chenho Tung, Jianping WangAbstract:: In this work, the structural fluctuations and Vibrational Energy Transfer dynamics in a supramolecular homodimer model, which is composed of 2-(9-anthracene)ureido-6-(1-undecyl)-4[1H]-pyrimidinone (UPAn) with quadruple intermolecular and single intramolecular hydrogen bonds (HBs), have been examined using ultrafast two-dimensional infrared (2D IR) and steady-state IR spectroscopies. A less structurally fluctuating intermolecular HB is found between the pyrimidinone C═O and ureido N-H groups. However, a larger structurally fluctuating intramolecular HB is suggested by the equilibrium and dynamical line-shape measurements of the ureido C═O stretch. Further, dynamical time-dependent 2D IR diagonal and off-diagonal signals show that intra- and intermolecular Vibrational Energy Transfer processes occur on the picosecond timescale, where the latter is more efficient due to intermolecular hydrogen bonding interaction and through-space interaction.
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ultrafast intermolecular Vibrational Energy Transfer in hexahydro 1 3 5 trinitro 1 3 5 triazine in molecular crystal by 2d ir spectroscopy
Journal of Physical Chemistry C, 2020Co-Authors: Pengyun Yu, Juan Zhao, Jianping WangAbstract:Cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine (HHTT) is an important energetic molecule with a variety of applications. In this work, structural dynamics and Vibrational-Energy Transfer dynamics of HHTT were investigated using steady-state infrared (IR), femtosecond time-resolved IR, and two-dimensional (2D) IR spectroscopic methods. Two different structural forms of HHTT (isolated molecules dissolved in DMSO and microcrystal dispersed in paraffin oil) were examined using the NO2 asymmetric stretching mode as a structural marker. Both intra- and intermolecular Vibrational Energy Transfers were observed in HHTT microcrystal, where the well-known α-conformation was retained. However, less perfect α-HHTT species was found in DMSO. An intermolecular Energy dissipation pathway was found to be related to Davydov splitting in the microcrystal form of HHTT, which originates from intermolecular interactions (e.g., electrostatic and hydrogen bonds). Experimental results were supported by quantum-chemistry co...
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ultrafast intermolecular Vibrational Energy Transfer in hexahydro 1 3 5 trinitro 1 3 5 triazine in molecular crystal by 2d ir spectroscopy
The Journal of Physical Chemistry, 2020Co-Authors: Pengyun Yu, Juan Zhao, Jianping WangAbstract:Cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine (HHTT) is an important energetic molecule with a variety of applications. In this work, structural dynamics and Vibrational-Energy Transfer dynamics of HHTT were investigated using steady-state infrared (IR), femtosecond time-resolved IR, and two-dimensional (2D) IR spectroscopic methods. Two different structural forms of HHTT (isolated molecules dissolved in DMSO and microcrystal dispersed in paraffin oil) were examined using the NO₂ asymmetric stretching mode as a structural marker. Both intra- and intermolecular Vibrational Energy Transfers were observed in HHTT microcrystal, where the well-known α-conformation was retained. However, less perfect α-HHTT species was found in DMSO. An intermolecular Energy dissipation pathway was found to be related to Davydov splitting in the microcrystal form of HHTT, which originates from intermolecular interactions (e.g., electrostatic and hydrogen bonds). Experimental results were supported by quantum-chemistry computations. In addition, both Vibrational excited-state relaxation and Vibrational Energy-Transfer processes were found to be more efficient in HHTT microcrystal than in the solvated form. Our work provides a chemical-bond level of insight into the nitro group-containing energetic materials.
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ultrafast intramolecular Vibrational Energy Transfer in carbon nitride hydrocolloid examined by femtosecond two dimensional infrared spectroscopy
Journal of Chemical Physics, 2019Co-Authors: Xuan Zheng, Pengyun Yu, Jianping WangAbstract:In this work, ultrafast Vibrational and structural processes in a graphitic carbon nitride hydrocolloid system were studied using a combination of linear infrared and nonlinear two-dimensional infrared (2D IR) spectroscopies. The experimentally observed three IR line shapes in the C=N stretching vibration frequency region were analyzed and attributed to the rigid and conjugated molecular frame of the prepared g-CN molecular species, which is believed to be a dimeric tris-s-triazine, as well as attributed to insignificant solvent influence on the delocalized C=N vibrations. Vibrational transition density cubes were also computed for the proposed g-CN dimer, confirming the heterocyclic C=N stretching nature of the three IR absorption peaks. Intramolecular Vibrational Energy Transfer dynamics and spectral diffusion of the g-CN system were characterized by examining a series of time-dependent 2D IR spectra. A picosecond intramolecular Vibrational Energy redistribution process was found to occur among these delocalized C=N stretching modes, acting as an efficient Vibrational Energy Transfer channel. This work reasonably connects the experimentally observed IR signature to a specific g-CN structure and also provides the first report on the ultrafast intramolecular processes of such carbon nitride systems. The obtained results are fundamentally important for understanding the molecular mechanisms of such carbon-nitride based functional materials.In this work, ultrafast Vibrational and structural processes in a graphitic carbon nitride hydrocolloid system were studied using a combination of linear infrared and nonlinear two-dimensional infrared (2D IR) spectroscopies. The experimentally observed three IR line shapes in the C=N stretching vibration frequency region were analyzed and attributed to the rigid and conjugated molecular frame of the prepared g-CN molecular species, which is believed to be a dimeric tris-s-triazine, as well as attributed to insignificant solvent influence on the delocalized C=N vibrations. Vibrational transition density cubes were also computed for the proposed g-CN dimer, confirming the heterocyclic C=N stretching nature of the three IR absorption peaks. Intramolecular Vibrational Energy Transfer dynamics and spectral diffusion of the g-CN system were characterized by examining a series of time-dependent 2D IR spectra. A picosecond intramolecular Vibrational Energy redistribution process was found to occur among these de...
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efficient Vibrational Energy Transfer through covalent bond in indigo carmine revealed by nonlinear ir spectroscopy
Journal of Physical Chemistry B, 2017Co-Authors: Xuemei He, Pengyun Yu, Juan Zhao, Jianping WangAbstract:Ultrafast Vibrational relaxation and structural dynamics of indigo carmine in dimethyl sulfoxide were examined using femtosecond pump–probe infrared and two-dimensional infrared (2D IR) spectroscopies. Using the intramolecularly hydrogen-bonded C═O and delocalized C═C stretching modes as infrared probes, local structural and dynamical variations of this blue dye molecule were observed. Energy relaxation of the Vibrationally excited C═O stretching mode was found to occur through covalent bond to the delocalized aromatic Vibrational modes on the time scale of a few picoseconds or less. Vibrational quantum beating was observed in magic-angle pump–probe, anisotropy, and 2D IR cross-peak dynamics, showing an oscillation period of ca. 1010 fs, which corresponds to the Energy difference between the C═O and C═C transition frequency (33 cm–1). This confirms a resonant Vibrational Energy Transfer happened between the two vibrators. However, a more efficient Energy-accepting mode of the excited C═O stretching was be...
Juan Zhao - One of the best experts on this subject based on the ideXlab platform.
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ultrafast Vibrational Energy Transfer through the covalent bond and intra and intermolecular hydrogen bonds in a supramolecular dimer by two dimensional infrared spectroscopy
Journal of Physical Chemistry B, 2020Co-Authors: Xueqian Dong, Pengyun Yu, Juan Zhao, Sumin Wang, Fan Yang, Lizhu Wu, Chenho Tung, Jianping WangAbstract:: In this work, the structural fluctuations and Vibrational Energy Transfer dynamics in a supramolecular homodimer model, which is composed of 2-(9-anthracene)ureido-6-(1-undecyl)-4[1H]-pyrimidinone (UPAn) with quadruple intermolecular and single intramolecular hydrogen bonds (HBs), have been examined using ultrafast two-dimensional infrared (2D IR) and steady-state IR spectroscopies. A less structurally fluctuating intermolecular HB is found between the pyrimidinone C═O and ureido N-H groups. However, a larger structurally fluctuating intramolecular HB is suggested by the equilibrium and dynamical line-shape measurements of the ureido C═O stretch. Further, dynamical time-dependent 2D IR diagonal and off-diagonal signals show that intra- and intermolecular Vibrational Energy Transfer processes occur on the picosecond timescale, where the latter is more efficient due to intermolecular hydrogen bonding interaction and through-space interaction.
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ultrafast intermolecular Vibrational Energy Transfer in hexahydro 1 3 5 trinitro 1 3 5 triazine in molecular crystal by 2d ir spectroscopy
Journal of Physical Chemistry C, 2020Co-Authors: Pengyun Yu, Juan Zhao, Jianping WangAbstract:Cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine (HHTT) is an important energetic molecule with a variety of applications. In this work, structural dynamics and Vibrational-Energy Transfer dynamics of HHTT were investigated using steady-state infrared (IR), femtosecond time-resolved IR, and two-dimensional (2D) IR spectroscopic methods. Two different structural forms of HHTT (isolated molecules dissolved in DMSO and microcrystal dispersed in paraffin oil) were examined using the NO2 asymmetric stretching mode as a structural marker. Both intra- and intermolecular Vibrational Energy Transfers were observed in HHTT microcrystal, where the well-known α-conformation was retained. However, less perfect α-HHTT species was found in DMSO. An intermolecular Energy dissipation pathway was found to be related to Davydov splitting in the microcrystal form of HHTT, which originates from intermolecular interactions (e.g., electrostatic and hydrogen bonds). Experimental results were supported by quantum-chemistry co...
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ultrafast intermolecular Vibrational Energy Transfer in hexahydro 1 3 5 trinitro 1 3 5 triazine in molecular crystal by 2d ir spectroscopy
Journal of Physical Chemistry C, 2020Co-Authors: Lu Shi, Juan Zhao, Jianping WangAbstract:Cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine (HHTT) is an important energetic molecule with a variety of applications. In this work, structural dynamics and Vibrational-Energy Transfer dyna...
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ultrafast intermolecular Vibrational Energy Transfer in hexahydro 1 3 5 trinitro 1 3 5 triazine in molecular crystal by 2d ir spectroscopy
The Journal of Physical Chemistry, 2020Co-Authors: Pengyun Yu, Juan Zhao, Jianping WangAbstract:Cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine (HHTT) is an important energetic molecule with a variety of applications. In this work, structural dynamics and Vibrational-Energy Transfer dynamics of HHTT were investigated using steady-state infrared (IR), femtosecond time-resolved IR, and two-dimensional (2D) IR spectroscopic methods. Two different structural forms of HHTT (isolated molecules dissolved in DMSO and microcrystal dispersed in paraffin oil) were examined using the NO₂ asymmetric stretching mode as a structural marker. Both intra- and intermolecular Vibrational Energy Transfers were observed in HHTT microcrystal, where the well-known α-conformation was retained. However, less perfect α-HHTT species was found in DMSO. An intermolecular Energy dissipation pathway was found to be related to Davydov splitting in the microcrystal form of HHTT, which originates from intermolecular interactions (e.g., electrostatic and hydrogen bonds). Experimental results were supported by quantum-chemistry computations. In addition, both Vibrational excited-state relaxation and Vibrational Energy-Transfer processes were found to be more efficient in HHTT microcrystal than in the solvated form. Our work provides a chemical-bond level of insight into the nitro group-containing energetic materials.
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central metal effect on intramolecular Vibrational Energy Transfer of m co 5br m mn re probed by two dimensional infrared spectroscopy
Physical Chemistry Chemical Physics, 2018Co-Authors: Fan Yang, Juan Zhao, Xueqian Dong, Minjun Feng, Jianping WangAbstract:Vibrational Energy Transfer in transition metal complexes with flexible structures in condensed phases is of central importance to catalytical chemistry processes. In this work, two molecules with different metal atoms, M(CO)5Br (where M = Mn, Re), were used as model systems, and their axial and radial carbonyl stretching modes as infrared probes. The central-metal effect on intramolecular Vibrational Energy redistribution (IVR) in M(CO)5Br was investigated in polar and nonpolar solvents. The linear infrared (IR) peak splitting between carbonyl vibrations increases as the metal atom changes from Mn to Re. The waiting-time dependent two-dimensional infrared diagonal- and off-diagonal peak amplitudes reveal a faster IVR process in Re(CO)5Br than in Mn(CO)5Br. With the aid of density functional theory (DFT) calculations, the central-metal effect on IVR time linearly correlates with the Vibrational coupling strength between the two involved modes. In addition, the polar solvent is found to accelerate the IVR process by affecting the anharmonic Vibrational potentials of a solute vibration mode.
Junrong Zheng - One of the best experts on this subject based on the ideXlab platform.
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nonresonant Vibrational Energy Transfer on metal nanoparticle liquid interface
Journal of Physical Chemistry C, 2016Co-Authors: Kaijun Yuan, Hailong Chen, Andrea Miranda, Yuneng Shen, Bo Jiang, Yajing Chen, Yufan Zhang, Xunmin Guo, Junrong ZhengAbstract:Knowledge of Vibrational Energy Transfer on a metal nanoparticle/liquid interface is essential for understanding the Energy conversion process involved in many heterogeneous nanocatalyses. In this study, we investigate mode-specific Vibrational Energy Transfer between CO molecules on different adsorbate sites on a 1 nm platinum metal nanoparticle/liquid interface by using ultrafast two-dimensional IR spectroscopy. The Vibrational Energy transport is found to be induced by vibration/vibration coupling with very little surface electron/vibration mediation. The Energy Transfer rate is determined to be about 1/140 ps–1 from the atop site CO to the bridge site CO, and the specific rate is around 1/400 ps–1 between the two nearest adsorbates. The Energy Transfer between different adsorbate sites can be described by the dephasing mechanism reasonably well. The mechanical coupling may contribute to the Transfer, but analyses suggest that the role of dipole/dipole interaction is a more important factor for the ene...
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Vibrational Energy Transfer an angstrom molecular ruler in studies of ion pairing and clustering in aqueous solutions
Journal of Physical Chemistry B, 2015Co-Authors: Hailong Chen, Hongtao Bian, Xiewen Wen, Wei Zhuang, Qiang Zhang, Junrong ZhengAbstract:The methodology and principle using Vibrational Energy Transfer to measure molecular distances in liquids are introduced. The application of the method to the studies of ion pairing and clustering in strong electrolyte aqueous solutions is demonstrated with MSCN aqueous solutions where M = Li, Na, K, Cs, and NH4. Experiments suggest that ions in the concentrated aqueous solutions can form substantial quantities of ion clusters in which both cations and anions are involved. More and larger clusters form in solutions that are relatively more concentrated and which include a larger cation. In KSCN solutions, the shortest anionic distance in the ion clusters is the same as that in the KSCN crystal. The rotational time of the anion and the nonresonant Vibrational Energy Transfer time with a gap of 75 cm–1 in the KSCN saturated solution are very similar to those in the KSCN crystal. However, the KSCN ion clusters are closer in structure to the melt. The clusters form an interconnected network with random ionic ...
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ion clustering in aqueous solutions probed with Vibrational Energy Transfer
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Hongtao Bian, Xiewen Wen, Hailong Chen, Suzee Han, Xiuquan Sun, Jian Song, Wei Zhuang, Junrong ZhengAbstract:Despite prolonged scientific efforts to unravel the hydration structures of ions in water, many open questions remain, in particular concerning the existences and structures of ion clusters in 1∶1 strong electrolyte aqueous solutions. A combined ultrafast 2D IR and pump/probe study through Vibrational Energy Transfers directly observes ion clustering in aqueous solutions of LiSCN, NaSCN, KSCN and CsSCN. In a near saturated KSCN aqueous solution (water/KSCN molar ratio = 2.4/1), 95% of the anions form ion clusters. Diluting the solution results in fewer, smaller, and tighter clusters. Cations have significant effects on cluster formation. A small cation results in smaller and fewer clusters. The Vibrational Energy Transfer method holds promise for studying a wide variety of other fast short-range molecular interactions.
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mode specific intermolecular Vibrational Energy Transfer ii deuterated water and potassium selenocyanate mixture
Journal of Chemical Physics, 2010Co-Authors: Hongtao Bian, Xiewen Wen, Junrong ZhengAbstract:Vibrational Energy Transfer from the first excited state (2635 cm−1) of the O–D stretch of deuterated water (D2O) to the 0-1 transition (2075 cm−1) of the CN stretch of potassium selenocyanate (KSeCN) in their 2.5:1 liquid mixture was observed with a multiple-mode two dimensional infrared spectroscopic technique. Despite the big Energy mismatch (560 cm−1) between the two modes, the Transfer is still very efficient with a time constant of 20 ps. The efficient Energy Transfer is probably because of the large excitation coupling between the two modes. The coupling is experimentally determined to be 176 cm−1. An approximate analytical equation derived from the Landau–Teller formula is applied to calculate the Energy Transfer rate with all parameters experimentally determined. The calculation results are qualitatively consistent with the experimental data.
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Mode-specific intermolecular Vibrational Energy Transfer. I. Phenyl selenocyanate and deuterated chloroform mixture
The Journal of Chemical Physics, 2010Co-Authors: Hongtao Bian, Xiewen Wen, Junrong ZhengAbstract:Vibrational Energy Transfer from the first excited state (2252 cm−1) of the C–D stretch of deuterated chloroform (DCCl3) to the 0-1 transition (2155 cm−1) of the CN stretch of phenyl selenocyanate (C6H5SeCN) in their 1:1 liquid mixture was observed with a pump/probe two-color two dimensional infrared spectroscopic technique. The mode-specific Energy Transfer can occur mainly because of the long Vibrational lifetime of the CN stretch first excited state (∼300 ps) and the relatively strong hydrogen-bond between the C–D and CN (calculated H-bond formation Energy in gas phase ∼−5.4 kcal/mol). The mode-specific Energy Transfer is relatively low efficient (only ∼2%), which is mainly because of the relatively short Vibrational lifetime (∼9 ps) of the C–D stretch first excited state and the big donor/acceptor Energy mismatch (97 cm−1) and the slow Transfer kinetics (1/kCD→CN=330 ps).
Peter Hamm - One of the best experts on this subject based on the ideXlab platform.
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a closer look into the distance dependence of Vibrational Energy Transfer on surfaces using 2d ir spectroscopy
Journal of Chemical Physics, 2020Co-Authors: Ricardo Fernandezteran, Peter HammAbstract:Vibrational Energy Transfer (VET) between two isotopologues of [Re(dcb)(CO)3Br] immobilized on a TiO2 surface is studied with the help of 2D IR spectroscopy in dependence of surface coverage. To dilute the molecules on the surface, and thereby control the intermolecular distances, two different diluents have been used: a third isotopologue of the same molecule and 4-cyanobenzoic acid. As expected, the VET rate decreases with dilution. For a quantitative investigation of the distance dependence of the VET rate, we analyze the data based on an excitonic model. This model reveals the typical 1/r6-distance dependence for a dimer of a donor and acceptor, similar to the nuclear Overhauser effect in NMR spectroscopy or Forster resonant Energy Transfer in electronic spectroscopy. However, VET becomes a collective phenomenon on the surface, with the existence of a network of coupled molecules and its disappearance below a percolation threshold, dominating the concentration dependence of the VET rate.
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plasmonic substrates do not promote Vibrational Energy Transfer at solid liquid interfaces
Journal of Physical Chemistry Letters, 2018Co-Authors: Jan Philip Kraack, Laurent Severy, David S Tilley, Peter HammAbstract:Intermolecular Vibrational Energy Transfer in monolayers of isotopically mixed rhenium carbonyl complexes at solid–liquid interfaces is investigated with the help of ultrafast 2D Attenuated Total Reflectance Infrared (2D ATR IR) spectroscopy in dependence of plasmonic surface enhancement effects. Dielectric and plasmonic materials are used to demonstrate that plasmonic effects have no impact on the Vibrational Energy Transfer rate in a regime of moderate IR surface enhancement (enhancement factors up to ca. 30). This result can be explained with the common image-dipole picture. The Vibrational Energy Transfer rate thus can be used as a direct observable to determine intermolecular distances on surfaces, regardless of their plasmonic properties.
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ultrafast Vibrational Energy Transfer in catalytic monolayers at solid liquid interfaces
Journal of Physical Chemistry Letters, 2017Co-Authors: Jan Philip Kraack, Angelo Frei, Roger Alberto, Peter HammAbstract:We investigate the ultrafast Vibrational dynamics of monolayers from adsorbed rhenium–carbonyl CO2-reduction catalysts on a semiconductor surface (indium–tin-oxide (ITO)) with ultrafast two-dimensional attenuated total reflection infrared (2D ATR IR) spectroscopy. The complexes are partially equipped with isotope-labeled (13C) carbonyl ligands to generate two spectroscopically distinguishable forms of the molecules. Ultrafast Vibrational Energy Transfer between the molecules is observed via the temporal evolution of cross-peaks between their symmetric carbonyl stretching vibrations. These contributions appear with time constant of 70 and 90 ps for downhill and uphill Energy Transfer, respectively. The Energy Transfer is thus markedly slower than any of the other intramolecular dynamics. From the Transfer rate, an intermolecular distance of ∼4–5 A can be estimated, close to the van der Waals distance of the molecular head groups. The present paper presents an important cornerstone for a better understandin...
