A photoexcited molecule is deactivated through a variety of photo-physical/chemical processes, and ultimately relaxes to the ground electronic state (S0) or further undergoes chemical reactions in S0. Time-resolved photoelectron imaging (TRPEI) [1] enables full observation of these photoinduced dynamics, because photoionization can be induced from any part of the potential energy surfaces (PESs). However, observation of low-lying electronic excited states and S0 requires probe pulses in the vacuum ultraviolet (VUV) region, and it has been difficult to generate intense ultrashort VUV laser pulses. Following the generation of sub-20 fs deep UV (DUV) pulses at 4.7 and 6.3 eV by cascaded filamentation four-wave mixing (FWM) [2], we have succeeded in generating ultrashort DUV and VUV (7.8 and 9.3 eV) pulses simultaneously [3,4]. While this light source is simple and easily implemented (Fig. 1), it provides multiple colors with ultrashort time-duration (<20 fs) without any dispersion control (Fig. 2). Thus, it is an ideal light for TRPEI. In this talk, we present TRPEI using ultrashort VUV pulses to obtain a “global reaction map” of photoinduced dynamics of an isolated molecule.
{"title":"Time-resolved Photoelectron Imaging Using Ultrashort VUV Pulses","authors":"T. Horio","doi":"10.3175/MOLSCI.12.A0097","DOIUrl":"https://doi.org/10.3175/MOLSCI.12.A0097","url":null,"abstract":"A photoexcited molecule is deactivated through a variety of photo-physical/chemical processes, and ultimately relaxes to the ground electronic state (S0) or further undergoes chemical reactions in S0. Time-resolved photoelectron imaging (TRPEI) [1] enables full observation of these photoinduced dynamics, because photoionization can be induced from any part of the potential energy surfaces (PESs). However, observation of low-lying electronic excited states and S0 requires probe pulses in the vacuum ultraviolet (VUV) region, and it has been difficult to generate intense ultrashort VUV laser pulses. Following the generation of sub-20 fs deep UV (DUV) pulses at 4.7 and 6.3 eV by cascaded filamentation four-wave mixing (FWM) [2], we have succeeded in generating ultrashort DUV and VUV (7.8 and 9.3 eV) pulses simultaneously [3,4]. While this light source is simple and easily implemented (Fig. 1), it provides multiple colors with ultrashort time-duration (<20 fs) without any dispersion control (Fig. 2). Thus, it is an ideal light for TRPEI. In this talk, we present TRPEI using ultrashort VUV pulses to obtain a “global reaction map” of photoinduced dynamics of an isolated molecule.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"56 4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91143043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
When hot molecular ions are isolated in vacuum, they cool solely by radiative processes. Recent experiments using electrostatic ion storage rings deepen the understanding of such slow processes.We will show how the electronic transi-tion triggered by the inverse internal conversion works in the even-numbered carbon cluster anions.Theoretical frame-work for estimating the radiative cooling rates, vibrational and electronic, is briefly introduced.
{"title":"Cooling of Molecular Ions by Recurrent Fluorescence","authors":"H. Shiromaru, N. Kono, T. Furukawa, T. Azuma","doi":"10.3175/MOLSCI.12.A0100","DOIUrl":"https://doi.org/10.3175/MOLSCI.12.A0100","url":null,"abstract":"When hot molecular ions are isolated in vacuum, they cool solely by radiative processes. Recent experiments using electrostatic ion storage rings deepen the understanding of such slow processes.We will show how the electronic transi-tion triggered by the inverse internal conversion works in the even-numbered carbon cluster anions.Theoretical frame-work for estimating the radiative cooling rates, vibrational and electronic, is briefly introduced.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"81 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74845862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Elucidation of the behaviors of complex molecular systems is central to controlling their elaborate functions. It requires approaches that bear time and space specificities as well as chemical specificity, because various kinds of molecules act at different times and locations in order to carry out particular molecular processes. Timeand spaceresolved vibrational spectroscopies are a powerful method that can meet all of these requirements. This Account shows how these approaches enable us to investigate complex molecular systems including living cells, bacterial communities known as biofilms, and solar-cell materials. Raman microspectroscopy in combination with multivariate data analysis reveals dynamic changes in the concentrations and distributions of cellular components such as proteins and lipids, during the cell cycle without the need for labeling. It is also applied to study bacterial biofilms in a nondestructive manner with a focus on their metabolites (carotenoids in the present case). Nanosecond time-resolved IR spectroscopy is used to observe distinct transient species generated after photoexcitation in organic– inorganic hybrid perovskite solar cells, which are attracting tremendous interest of researchers as a promising next-generation photovoltaic device. The results presented here highlight that deciphering timeand space-resolved vibrational spectra has unraveled a number of new phenomena that are of relevance to biological/material functions.
{"title":"Time- and Space-Resolved Vibrational Spectroscopic Approaches to Elucidate the Behaviors of Complex Molecular Systems: From Biological Cells to Hybrid Solar-Cell Materials: ―細胞からハイブリッド太陽電池材料まで―","authors":"Shinsuke Shigeto","doi":"10.3175/MOLSCI.12.A0099","DOIUrl":"https://doi.org/10.3175/MOLSCI.12.A0099","url":null,"abstract":"Elucidation of the behaviors of complex molecular systems is central to controlling their elaborate functions. It requires approaches that bear time and space specificities as well as chemical specificity, because various kinds of molecules act at different times and locations in order to carry out particular molecular processes. Timeand spaceresolved vibrational spectroscopies are a powerful method that can meet all of these requirements. This Account shows how these approaches enable us to investigate complex molecular systems including living cells, bacterial communities known as biofilms, and solar-cell materials. Raman microspectroscopy in combination with multivariate data analysis reveals dynamic changes in the concentrations and distributions of cellular components such as proteins and lipids, during the cell cycle without the need for labeling. It is also applied to study bacterial biofilms in a nondestructive manner with a focus on their metabolites (carotenoids in the present case). Nanosecond time-resolved IR spectroscopy is used to observe distinct transient species generated after photoexcitation in organic– inorganic hybrid perovskite solar cells, which are attracting tremendous interest of researchers as a promising next-generation photovoltaic device. The results presented here highlight that deciphering timeand space-resolved vibrational spectra has unraveled a number of new phenomena that are of relevance to biological/material functions.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81449119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soft X-ray absorption spectroscopy (XAS) is an element specific method to reveal local structures of liquid samples since soft X-ray below 1 keV has chemically important absorption edges such as C, N, and O K-edges, and L-edges of transition metals. In aqueous solutions, interactions of organic molecules are measured in C and N K-edges and solvent water is separately observed in O K-edge. However, it is difficult to measure XAS of liquid in transmission mode since the thickness of a liquid layer should be less than 1 µm due to large soft X-ray absorption coefficient of liquid. We have successfully developed a liquid flow cell for XAS in transmission mode, where the absorbance of liquid samples can be easily optimized by controlling the liquid thickness. In this review, we report on the temperature dependent change of hydrogen bond in liquid water by O K-edge XAS and intermolecular interactions of pyridine with water in aqueous pyridine solutions at different molar fractions by using XAS in C, N, and O K-edges. For the operando observation of electrochemical reaction, we have developed an electrochemical cell with built-in electrodes and measured Fe L-edge XAS of aqueous iron sulfate solutions during electrochemical reaction under the same scan rate as in cyclic voltammetry. For understanding the phase transition mechanism, not only the mixed phase but also liquid-liquid interfaces after phase transition should be investigated by spatially resolved XAS. We have developed a liquid flow cell that is set in a scanning transmission X-ray microscope. The mechanism of a lower critical solution temperature in aqueous triethylamine solution is studied by spatially resolved XAS of the liquid-liquid interfaces between triethylamine and water phases with the spatial resolution of 140 nm.
{"title":"Operando Observation of Liquid and Liquid-Liquid Interface by Soft X-ray Absorption Spectroscopy","authors":"M. Nagasaka","doi":"10.3175/MOLSCI.12.A0096","DOIUrl":"https://doi.org/10.3175/MOLSCI.12.A0096","url":null,"abstract":"Soft X-ray absorption spectroscopy (XAS) is an element specific method to reveal local structures of liquid samples since soft X-ray below 1 keV has chemically important absorption edges such as C, N, and O K-edges, and L-edges of transition metals. In aqueous solutions, interactions of organic molecules are measured in C and N K-edges and solvent water is separately observed in O K-edge. However, it is difficult to measure XAS of liquid in transmission mode since the thickness of a liquid layer should be less than 1 µm due to large soft X-ray absorption coefficient of liquid. We have successfully developed a liquid flow cell for XAS in transmission mode, where the absorbance of liquid samples can be easily optimized by controlling the liquid thickness. In this review, we report on the temperature dependent change of hydrogen bond in liquid water by O K-edge XAS and intermolecular interactions of pyridine with water in aqueous pyridine solutions at different molar fractions by using XAS in C, N, and O K-edges. For the operando observation of electrochemical reaction, we have developed an electrochemical cell with built-in electrodes and measured Fe L-edge XAS of aqueous iron sulfate solutions during electrochemical reaction under the same scan rate as in cyclic voltammetry. For understanding the phase transition mechanism, not only the mixed phase but also liquid-liquid interfaces after phase transition should be investigated by spatially resolved XAS. We have developed a liquid flow cell that is set in a scanning transmission X-ray microscope. The mechanism of a lower critical solution temperature in aqueous triethylamine solution is studied by spatially resolved XAS of the liquid-liquid interfaces between triethylamine and water phases with the spatial resolution of 140 nm.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84215521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this accounts, we summarize recent progress in experimental approaches to the investigation of the unoccupied electronic structures of organic ultrathin films, based on a combination of spectroscopic and microscopic techniques. On the occupied valence bands of the films, it has been extensively studied for a variety of organic molecules. However, systematic investigations of unoccupied electronic states still have been challenging because experimental techniques are limited. In this context, we have clarified the correlation between geometric and electronic structure using a combination of two-photon photoemission (2PPE) spectroscopy and scanning tunneling microscopy (STM). By using 2PPE, one can measure unoccupied states as well as occupied states in the vicinity of the Fermi level. Beyond the diffraction limit of light, STM can be a powerful means of mapping unoccupied electronic structures, not limited to the imaging of geometrical structures. Depending on the molecular density and substrate temperature, organic ultrathin films of polycyclic aromatic hydrocarbons on graphite substrates show a variety of structures, as demonstrated by microscopic observations on the nanoscale. It is apparent that the geometrical structures, especially molecular orientations as stressed throughout this accounts, have a strong impact on both occupied and unoccupied electronic structures. These findings, with a spectroscopic and microscopic understanding at the level of molecule, will provide fundamental insights into desirable electronic properties at organic/substrate interfaces. つ有機超薄膜の表面電子状態を理解することは分子科学と
{"title":"Unoccupied States Measurements, Spatial Mapping, and Nanoscale Structures of Organic Ultrathin Films","authors":"Takashi Yamada","doi":"10.3175/MOLSCI.12.A0098","DOIUrl":"https://doi.org/10.3175/MOLSCI.12.A0098","url":null,"abstract":"In this accounts, we summarize recent progress in experimental approaches to the investigation of the unoccupied electronic structures of organic ultrathin films, based on a combination of spectroscopic and microscopic techniques. On the occupied valence bands of the films, it has been extensively studied for a variety of organic molecules. However, systematic investigations of unoccupied electronic states still have been challenging because experimental techniques are limited. In this context, we have clarified the correlation between geometric and electronic structure using a combination of two-photon photoemission (2PPE) spectroscopy and scanning tunneling microscopy (STM). By using 2PPE, one can measure unoccupied states as well as occupied states in the vicinity of the Fermi level. Beyond the diffraction limit of light, STM can be a powerful means of mapping unoccupied electronic structures, not limited to the imaging of geometrical structures. Depending on the molecular density and substrate temperature, organic ultrathin films of polycyclic aromatic hydrocarbons on graphite substrates show a variety of structures, as demonstrated by microscopic observations on the nanoscale. It is apparent that the geometrical structures, especially molecular orientations as stressed throughout this accounts, have a strong impact on both occupied and unoccupied electronic structures. These findings, with a spectroscopic and microscopic understanding at the level of molecule, will provide fundamental insights into desirable electronic properties at organic/substrate interfaces. つ有機超薄膜の表面電子状態を理解することは分子科学と","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"64 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75473495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Developments on Large-Scale Fine Synthesis Methods for Nanocluster Materials Science","authors":"H. Tsunoyama","doi":"10.3175/MOLSCI.11.A0091","DOIUrl":"https://doi.org/10.3175/MOLSCI.11.A0091","url":null,"abstract":"","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"130 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87906951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
【Abstract】Electron spectroscopy combined with a scattering experiment offers a powerful means to study spatial characteristics of a one-electron wavefunction in molecules or in continuum states. Here we review recent developments in such multi-dimensional electron spectroscopy studies which utilize atomic, photonic, and electronic collisions. In addition, we also review our recent efforts towards development of time-resolved electron momentum spectroscopy that employs femtosecond laser and picosecond electron pulses in a pump-probe scheme. In spite of the low data statistics as well as of the limited experimental resolutions, it has been clearly demonstrated that measurements of electron momentum profiles of short-lived transient species are feasible, opening the door to time-resolved orbital imaging in momentum space.
{"title":"Molecular Orbital Imaging by Multi-Dimensional Electron Spectroscopy","authors":"M. Yamazaki","doi":"10.3175/MOLSCI.11.A0093","DOIUrl":"https://doi.org/10.3175/MOLSCI.11.A0093","url":null,"abstract":"【Abstract】Electron spectroscopy combined with a scattering experiment offers a powerful means to study spatial characteristics of a one-electron wavefunction in molecules or in continuum states. Here we review recent developments in such multi-dimensional electron spectroscopy studies which utilize atomic, photonic, and electronic collisions. In addition, we also review our recent efforts towards development of time-resolved electron momentum spectroscopy that employs femtosecond laser and picosecond electron pulses in a pump-probe scheme. In spite of the low data statistics as well as of the limited experimental resolutions, it has been clearly demonstrated that measurements of electron momentum profiles of short-lived transient species are feasible, opening the door to time-resolved orbital imaging in momentum space.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82042123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Atomic structures of proteins, nucleic acids, and their complexes are determined using X-ray crystallography, NMR, or cryo-Electron Microscopy. These structures are essential to understand their structure-function relationships. However, the experimental conditions are totally different from the actual cellular environments and it is hard to understand how biomolecules behave in such cellular environments, just using the atomic structures. We have recently built protein crowding systems in computers and carried out all-atom molecular dynamics (MD) simulations of the systems to understand biomolecular dynamics in the crowded environments. The largest simulations we have ever performed were the all-atom MD simulations of a bacterial cytoplasm using K computer. By analyzing the simulation trajectories, we observed that non-specific protein-protein and protein-metabolite interactions play important roles in biomolecular dynamics and stability in a cell. The new insight from the simulations is useful not only for basic life science in molecular and cellular biology but also drug discovery in future for introducing the effect of non-specific protein-drug interactions.
{"title":"Molecular Dynamics Simulations of Biomolecules in Cellular Environments","authors":"Y. Sugita, I. Yu, M. Feig","doi":"10.3175/MOLSCI.11.A0094","DOIUrl":"https://doi.org/10.3175/MOLSCI.11.A0094","url":null,"abstract":"Atomic structures of proteins, nucleic acids, and their complexes are determined using X-ray crystallography, NMR, or cryo-Electron Microscopy. These structures are essential to understand their structure-function relationships. However, the experimental conditions are totally different from the actual cellular environments and it is hard to understand how biomolecules behave in such cellular environments, just using the atomic structures. We have recently built protein crowding systems in computers and carried out all-atom molecular dynamics (MD) simulations of the systems to understand biomolecular dynamics in the crowded environments. The largest simulations we have ever performed were the all-atom MD simulations of a bacterial cytoplasm using K computer. By analyzing the simulation trajectories, we observed that non-specific protein-protein and protein-metabolite interactions play important roles in biomolecular dynamics and stability in a cell. The new insight from the simulations is useful not only for basic life science in molecular and cellular biology but also drug discovery in future for introducing the effect of non-specific protein-drug interactions.","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"47 2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90052162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Things Coming Up to Mind during Development of Time- and Space-resolved Measurements","authors":"H. Fukumura","doi":"10.3175/MOLSCI.11.A0095","DOIUrl":"https://doi.org/10.3175/MOLSCI.11.A0095","url":null,"abstract":"","PeriodicalId":19105,"journal":{"name":"Molecular Science","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85202051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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