A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:
Theoretical study on resonance Raman scattering for C60molecules in benzene solutions
23 October 2011, 03:05:06
Publication year: 2011
Source: Vibrational Spectroscopy, Available online 21 October 2011
Ren-hui Zheng, Wen-mei Wei, Yuan-yuan Sun, Qiang Shi
Resonance Raman spectra for C60molecules in vacuum and benzene solutions have been studied based on density functional theory calculations underIhsymmetry. The displacement parameters of the potential energy minimum along normal coordinates between the ground and excited states for totally symmetric modes are determined, which are small. The solvent effect is found to have a slight influence on Raman intensities. Also, resonance Raman excitation profiles have been investigated.
Source: Vibrational Spectroscopy, Available online 21 October 2011
Ren-hui Zheng, Wen-mei Wei, Yuan-yuan Sun, Qiang Shi
Resonance Raman spectra for C60molecules in vacuum and benzene solutions have been studied based on density functional theory calculations underIhsymmetry. The displacement parameters of the potential energy minimum along normal coordinates between the ground and excited states for totally symmetric modes are determined, which are small. The solvent effect is found to have a slight influence on Raman intensities. Also, resonance Raman excitation profiles have been investigated.
Spectral inter-conversion analysis of thermally induced structural changes in polyethylene crystals
23 October 2011, 03:05:06
Publication year: 2011
Source: Vibrational Spectroscopy, Available online 21 October 2011
Liping Zhang, Shin Watanabe, Isao Noda, Yuqing Wu
Temperature dependence of conformational disordering in crystals of polyethylene was investigated by the inter-conversion analysis based on the combination of NIR and MIR spectra by means of the partial least-squares regression (PLS2). Two regression models were built based on the spectral range of 1500 - 1250 cmand 4400 - 4200 cmto make the prediction in a wider spectral range. The other models were explored in the relatively narrow two MIR range of 1365 - 1355 and 1471 - 1461 cm(due to the hexagonal phase); and three NIR range of 4354 - 4344 (corresponding to the hexagonal phase), 4327 - 4317 (relating to the orthorhombic phase) and 4261 - 4251 cm(previously unconfirmed conformation). Total of twelve PLS2 models were built based on these infrared spectral ranges and used to carry out the spectral inter-conversion analysis. By spectral inter-conversion, the conformational disordering induced by thermal stimulus was clearly differentiated, and the assignment of a band at 4256 cmin the NIR spectral range was confirmed. The qualitative analysis indicates that the temperature dependency of the band at 4256 cmin the NIR range is very similar to that of the bands at 1360 and 4349 cm(which corresponded to the hexagonal phase) indicating they have the common spectral origin. The quantitative comparison of the prediction deviation values between different multivariate spectral models firmly validate the assignment of the band at 4256 cmto the hexagonal sequence formed in the thermally induced conformational disordering.
Source: Vibrational Spectroscopy, Available online 21 October 2011
Liping Zhang, Shin Watanabe, Isao Noda, Yuqing Wu
Temperature dependence of conformational disordering in crystals of polyethylene was investigated by the inter-conversion analysis based on the combination of NIR and MIR spectra by means of the partial least-squares regression (PLS2). Two regression models were built based on the spectral range of 1500 - 1250 cmand 4400 - 4200 cmto make the prediction in a wider spectral range. The other models were explored in the relatively narrow two MIR range of 1365 - 1355 and 1471 - 1461 cm(due to the hexagonal phase); and three NIR range of 4354 - 4344 (corresponding to the hexagonal phase), 4327 - 4317 (relating to the orthorhombic phase) and 4261 - 4251 cm(previously unconfirmed conformation). Total of twelve PLS2 models were built based on these infrared spectral ranges and used to carry out the spectral inter-conversion analysis. By spectral inter-conversion, the conformational disordering induced by thermal stimulus was clearly differentiated, and the assignment of a band at 4256 cmin the NIR spectral range was confirmed. The qualitative analysis indicates that the temperature dependency of the band at 4256 cmin the NIR range is very similar to that of the bands at 1360 and 4349 cm(which corresponded to the hexagonal phase) indicating they have the common spectral origin. The quantitative comparison of the prediction deviation values between different multivariate spectral models firmly validate the assignment of the band at 4256 cmto the hexagonal sequence formed in the thermally induced conformational disordering.
Mechanisms of energy dissipation and ultrafast primary events in photostable systems: H-bond, excess electron, biological photoreceptors
23 October 2011, 03:05:06
Publication year: 2011
Source: Vibrational Spectroscopy, Available online 21 October 2011
Halina Abramczyk
The fundamental property of biological systems is photostability. Without photostability no life would be possible. Molecular structures responsible for harvesting of the solar energy must be photostable and resistant to photo-induced chemical changes or must find a way for a recovery. To answer the questions about the photostability we have to understand mechanisms of relaxation and energy dissipation upon an optical excitation. There is a common agreement that such channels are provided by some special features of the potential energy surfaces including the conical intersections. The mechanism that leads to decrease in the energy gap between the excited-state potential and the ground state energy surfaces is related to the coupling between the excited state (electronic or vibrational) and the intramolecular and intermolecular vibrational modes. When the potential energy surfaces approach each other nonadiabatic transitions are facilitated by their close proximity and the rate of radiationless transitions increases. The mechanism seems to be universal both for simple species such as H-bond systems, solvated electrons, and biologically important photoreceptor proteins such as bacteriorhodopsin. In order to study energy dissipation and dynamical alterations in the structure, a system is triggered with laser and monitored with excellent time-resolution. Ultrafast spectroscopies have played an important role in the study of a number of biological processes and have provided unique information about primary events and the mechanism of energy relaxation. Biological activity of molecules is frequently initiated by elementary chemical reactions such as energy and electron transfer, cis-trans isomerizations, or proton transfer. Many of these reactions are usually very fast and efficient and occur on picosecond and femtosecond timescales. This paper reviews recent progress of understanding light-energy collection and dissipation, with a special emphasis on the role of the vibronic coupling in H-bonded systems, solvated electrons and light-initiated biological photoreceptors. We will concentrate on the spectroscopic methods based on the linear and nonlinear responses such as the time resolved coherent anti-Stokes Raman spectroscopy (CARS) and the pump-probe transient femtosecond absorption spectroscopy. Detailed understanding the paths of energy dissipation will reveal mechanisms that mediate light-induced signal transduction as well as the role of photoreceptors in photostability protection and reparation mechanisms in living cells.
Source: Vibrational Spectroscopy, Available online 21 October 2011
Halina Abramczyk
The fundamental property of biological systems is photostability. Without photostability no life would be possible. Molecular structures responsible for harvesting of the solar energy must be photostable and resistant to photo-induced chemical changes or must find a way for a recovery. To answer the questions about the photostability we have to understand mechanisms of relaxation and energy dissipation upon an optical excitation. There is a common agreement that such channels are provided by some special features of the potential energy surfaces including the conical intersections. The mechanism that leads to decrease in the energy gap between the excited-state potential and the ground state energy surfaces is related to the coupling between the excited state (electronic or vibrational) and the intramolecular and intermolecular vibrational modes. When the potential energy surfaces approach each other nonadiabatic transitions are facilitated by their close proximity and the rate of radiationless transitions increases. The mechanism seems to be universal both for simple species such as H-bond systems, solvated electrons, and biologically important photoreceptor proteins such as bacteriorhodopsin. In order to study energy dissipation and dynamical alterations in the structure, a system is triggered with laser and monitored with excellent time-resolution. Ultrafast spectroscopies have played an important role in the study of a number of biological processes and have provided unique information about primary events and the mechanism of energy relaxation. Biological activity of molecules is frequently initiated by elementary chemical reactions such as energy and electron transfer, cis-trans isomerizations, or proton transfer. Many of these reactions are usually very fast and efficient and occur on picosecond and femtosecond timescales. This paper reviews recent progress of understanding light-energy collection and dissipation, with a special emphasis on the role of the vibronic coupling in H-bonded systems, solvated electrons and light-initiated biological photoreceptors. We will concentrate on the spectroscopic methods based on the linear and nonlinear responses such as the time resolved coherent anti-Stokes Raman spectroscopy (CARS) and the pump-probe transient femtosecond absorption spectroscopy. Detailed understanding the paths of energy dissipation will reveal mechanisms that mediate light-induced signal transduction as well as the role of photoreceptors in photostability protection and reparation mechanisms in living cells.
No comments:
Post a Comment