Pub Date : 2020-01-02DOI: 10.1080/0144235X.2019.1691319
S. Vyazovkin
The kinetics of thermal decomposition of solids is discussed in connection with three major approaches to inducing pressure: by manipulating pressure of the product gas, by changing pressure of an inert gas, and by applying a mechanical force. The first two approaches are implemented in differential scanning calorimetry (DSC) and thermogravimetry (TGA), whose upper pressure limit is in the MPa range. The third approach is implemented in diamond anvil cells that extend measurements to the GPa range. In the GPa range a response of the rate to pressure is determined by the sign of the activation volume change. In the MPa range this response is determined by pressure of the gaseous product in the reaction zone. Manipulating the product gas pressure affects directly the kinetics of reversible decompositions as described by a number of models. Changing pressure of an inert gas results in indirect manipulation of pressure of the gaseous products that can engage in reaction with the reactant or another product and thus affect the kinetics of autocatalytic and reversible decompositions. These and other effects are discussed with the emphasis on changes in the activation energy and preexponential factor as a function of pressure, temperature, and conversion.
{"title":"Kinetic effects of pressure on decomposition of solids","authors":"S. Vyazovkin","doi":"10.1080/0144235X.2019.1691319","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1691319","url":null,"abstract":"The kinetics of thermal decomposition of solids is discussed in connection with three major approaches to inducing pressure: by manipulating pressure of the product gas, by changing pressure of an inert gas, and by applying a mechanical force. The first two approaches are implemented in differential scanning calorimetry (DSC) and thermogravimetry (TGA), whose upper pressure limit is in the MPa range. The third approach is implemented in diamond anvil cells that extend measurements to the GPa range. In the GPa range a response of the rate to pressure is determined by the sign of the activation volume change. In the MPa range this response is determined by pressure of the gaseous product in the reaction zone. Manipulating the product gas pressure affects directly the kinetics of reversible decompositions as described by a number of models. Changing pressure of an inert gas results in indirect manipulation of pressure of the gaseous products that can engage in reaction with the reactant or another product and thus affect the kinetics of autocatalytic and reversible decompositions. These and other effects are discussed with the emphasis on changes in the activation energy and preexponential factor as a function of pressure, temperature, and conversion.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81499432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-02DOI: 10.1080/0144235X.2020.1700083
M. P. M. Marques, A. L. M. B. D. Carvalho, A. P. Mamede, S. Rudić, A. Dopplapudi, V. G. Sakai, L. A. E. B. D. Carvalho
ABSTRACT Water is the major constituent of the human body and plays a vital role in biochemical processes. Even subtle variations in the structure or dynamics of intracellular water may be the driving force for disrupting homeostasis in the highly crowded intracellular milieu, which in turn may trigger biomolecular dysfunction eventually leading to cell death. This article highlights several studies on human cells and DNA, that establish intracellular water as a key mediator of cytotoxicity. Inelastic and quasi-elastic neutron scattering techniques were applied, which provide a direct probe, at the atomic scale, of the behaviour of both cytoplasmic and hydration water, in the presence and absence of drugs. While the primary targets of drugs are biological receptors, we propose water as a potential secondary target for chemotherapy. The methodology presented constitutes an innovative approach for chemotherapeutic research. In addition, it showcases the value of neutron spectroscopy, a traditionally physico-chemical tool, for clinically-relevant research.
{"title":"Intracellular water as a mediator of anticancer drug action","authors":"M. P. M. Marques, A. L. M. B. D. Carvalho, A. P. Mamede, S. Rudić, A. Dopplapudi, V. G. Sakai, L. A. E. B. D. Carvalho","doi":"10.1080/0144235X.2020.1700083","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1700083","url":null,"abstract":"ABSTRACT Water is the major constituent of the human body and plays a vital role in biochemical processes. Even subtle variations in the structure or dynamics of intracellular water may be the driving force for disrupting homeostasis in the highly crowded intracellular milieu, which in turn may trigger biomolecular dysfunction eventually leading to cell death. This article highlights several studies on human cells and DNA, that establish intracellular water as a key mediator of cytotoxicity. Inelastic and quasi-elastic neutron scattering techniques were applied, which provide a direct probe, at the atomic scale, of the behaviour of both cytoplasmic and hydration water, in the presence and absence of drugs. While the primary targets of drugs are biological receptors, we propose water as a potential secondary target for chemotherapy. The methodology presented constitutes an innovative approach for chemotherapeutic research. In addition, it showcases the value of neutron spectroscopy, a traditionally physico-chemical tool, for clinically-relevant research.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89839756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-02DOI: 10.1080/0144235X.2019.1678929
P. Ferrari, E. Janssens, P. Lievens, K. Hansen
Predicted almost forty years ago, the radiation from thermally populated excited electronic states has recently been recognised as an important cooling mechanism in free molecules and clusters. It has presently been observed from both inorganic clusters and carbon-based molecules in molecular beams and ion storage devices. Experiments have demonstrated that many of these systems radiate at rates approaching microsecond time scales, and often with a distinct dependence on the precise number of atoms in the system. The radiation acts as a strongly stabilising factor against both unimolecular decay and thermal electron emission. In astrophysical context, radiative cooling provides a mechanism to dissipate internal energy in star-forming processes, and stabilises molecules selectively in the circumstellar medium. The consequences of an active radiative cooling channel for nanoparticle production will likewise favour special sizes in non-equilibrium formation processes. In this review, the radiative cooling of clusters is presented and illustrated with examples of experiments performed on small carbon, metal, and semiconductor clusters, and on PAH molecules. The experimental and theoretical techniques used are discussed, together with the consequences of radiative cooling on size-to-size stability patterns of clusters.
{"title":"Radiative cooling of size-selected gas phase clusters","authors":"P. Ferrari, E. Janssens, P. Lievens, K. Hansen","doi":"10.1080/0144235X.2019.1678929","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1678929","url":null,"abstract":"Predicted almost forty years ago, the radiation from thermally populated excited electronic states has recently been recognised as an important cooling mechanism in free molecules and clusters. It has presently been observed from both inorganic clusters and carbon-based molecules in molecular beams and ion storage devices. Experiments have demonstrated that many of these systems radiate at rates approaching microsecond time scales, and often with a distinct dependence on the precise number of atoms in the system. The radiation acts as a strongly stabilising factor against both unimolecular decay and thermal electron emission. In astrophysical context, radiative cooling provides a mechanism to dissipate internal energy in star-forming processes, and stabilises molecules selectively in the circumstellar medium. The consequences of an active radiative cooling channel for nanoparticle production will likewise favour special sizes in non-equilibrium formation processes. In this review, the radiative cooling of clusters is presented and illustrated with examples of experiments performed on small carbon, metal, and semiconductor clusters, and on PAH molecules. The experimental and theoretical techniques used are discussed, together with the consequences of radiative cooling on size-to-size stability patterns of clusters.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2019-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88433055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We review our development on beyond Born–Oppenheimer (BBO) theory and its implementation on various models and realistic molecular processes as carried out over the last 15 years. The theoretical formulation leading to the BBO equations are thoroughly discussed with ab initio calculations. We have employed first principle based BBO theory not only to formulate single surface extended Born–Oppenheimer equation to understand the nature of nonadiabatic effect but also to construct accurate diabatic potential energy surfaces (PESs) for important spectroscopic systems, namely, NO radical, Na and K clusters, NO radical, benzene and 1,3,5-trifluorobenzene radical cations ( and ) as well as triatomic reactive scattering systems like and . The nonadiabatic phenomena like Jahn–Teller (JT), Renner–Teller, pseudo Jahn–Teller effects and the accidental conical intersections are the key players in dictating spectroscopic and reactive scattering profiles. The nature of diabatic coupling elements derived from ab initio data with BBO theory for molecular processes in Franck-Condon region has been analysed in the context of linearly and bilinearly coupled JT model Hamiltonian. The results obtained from quantum dynamical calculations on BBO based diabatic PESs of the above molecular systems are found to be in accord with available experimental outcomes.
{"title":"Beyond Born–Oppenheimer theory for spectroscopic and scattering processes","authors":"Bijit Mukherjee, Koushik Naskar, Soumya Mukherjee, Sandip Ghosh, Tapas Sahoo, S. Adhikari","doi":"10.1080/0144235X.2019.1672987","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1672987","url":null,"abstract":"We review our development on beyond Born–Oppenheimer (BBO) theory and its implementation on various models and realistic molecular processes as carried out over the last 15 years. The theoretical formulation leading to the BBO equations are thoroughly discussed with ab initio calculations. We have employed first principle based BBO theory not only to formulate single surface extended Born–Oppenheimer equation to understand the nature of nonadiabatic effect but also to construct accurate diabatic potential energy surfaces (PESs) for important spectroscopic systems, namely, NO radical, Na and K clusters, NO radical, benzene and 1,3,5-trifluorobenzene radical cations ( and ) as well as triatomic reactive scattering systems like and . The nonadiabatic phenomena like Jahn–Teller (JT), Renner–Teller, pseudo Jahn–Teller effects and the accidental conical intersections are the key players in dictating spectroscopic and reactive scattering profiles. The nature of diabatic coupling elements derived from ab initio data with BBO theory for molecular processes in Franck-Condon region has been analysed in the context of linearly and bilinearly coupled JT model Hamiltonian. The results obtained from quantum dynamical calculations on BBO based diabatic PESs of the above molecular systems are found to be in accord with available experimental outcomes.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2019-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86093519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-02DOI: 10.1080/0144235X.2019.1677062
F. Ruipérez
ABSTRACT The rapid development of computational hardware and software, as well as the advances in new theoretical methodologies have allowed quantum chemistry, in particular density functional theory, to become a fundamental tool in polymer science to predict, rationalise, develop and characterise polymeric materials. Quantum chemistry is able to provide insight into molecular properties for both electronic ground and excited states, allowing the rationalisation and prediction of reaction paths to understand chemical reactivity, redox processes or optical band gaps, to mention some. This review provides an overview of the computational studies performed using quantum chemical methods that highlight the key contributions in the field of polymer science.
{"title":"Application of quantum chemical methods in polymer chemistry","authors":"F. Ruipérez","doi":"10.1080/0144235X.2019.1677062","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1677062","url":null,"abstract":"ABSTRACT The rapid development of computational hardware and software, as well as the advances in new theoretical methodologies have allowed quantum chemistry, in particular density functional theory, to become a fundamental tool in polymer science to predict, rationalise, develop and characterise polymeric materials. Quantum chemistry is able to provide insight into molecular properties for both electronic ground and excited states, allowing the rationalisation and prediction of reaction paths to understand chemical reactivity, redox processes or optical band gaps, to mention some. This review provides an overview of the computational studies performed using quantum chemical methods that highlight the key contributions in the field of polymer science.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2019-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83531120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-03DOI: 10.1080/0144235X.2019.1663062
Emily L. Holt, V. Stavros
ABSTRACT Sunscreen formulations have been developed to provide an artificial protective barrier against the deleterious effects of overexposure to ultraviolet (UV) radiation in humans. Ultrafast pump-probe spectroscopy techniques have been an invaluable tool in recent years for determining the photochemistry of active ingredients in sunscreen formulations, predominantly UV filters, in both the gas- and solution-phases. These measurements have enabled the elucidation of molecular relaxation pathways and photoprotection mechanisms, which are in turn insightful for assessing a filter's photostability and suitability for sunscreen use. In this review, we discuss the benefits of a bottom-up approach: the progression from the study of UV filters for sunscreens in vacuum, away from the influences of any solvent; in solution, to investigate the relaxation pathways of potential sunscreen filters in closer to real-life conditions, whilst exploring the merits of selective functionalisation to improve their characteristics; and beyond, to current advances that are mimicking the application of sunscreen formulations to the surface of the skin.
{"title":"Applications of ultrafast spectroscopy to sunscreen development, from first principles to complex mixtures","authors":"Emily L. Holt, V. Stavros","doi":"10.1080/0144235X.2019.1663062","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1663062","url":null,"abstract":"ABSTRACT Sunscreen formulations have been developed to provide an artificial protective barrier against the deleterious effects of overexposure to ultraviolet (UV) radiation in humans. Ultrafast pump-probe spectroscopy techniques have been an invaluable tool in recent years for determining the photochemistry of active ingredients in sunscreen formulations, predominantly UV filters, in both the gas- and solution-phases. These measurements have enabled the elucidation of molecular relaxation pathways and photoprotection mechanisms, which are in turn insightful for assessing a filter's photostability and suitability for sunscreen use. In this review, we discuss the benefits of a bottom-up approach: the progression from the study of UV filters for sunscreens in vacuum, away from the influences of any solvent; in solution, to investigate the relaxation pathways of potential sunscreen filters in closer to real-life conditions, whilst exploring the merits of selective functionalisation to improve their characteristics; and beyond, to current advances that are mimicking the application of sunscreen formulations to the surface of the skin.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2019-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76252802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-03DOI: 10.1080/0144235X.2019.1660114
J. Prakash
ABSTRACT Surface enhanced Raman scattering (SERS) substrates, composed of plasmonic nanostructures (PNSs) and photocatalyst semiconductors, have emerged as novel multifunctional nanomaterials for advanced engineering applications. These combinations improve the photocatalytic activity of such systems and extend their application as recyclable SERS substrates owing to their self-cleaning ability by photodegradation of analyte molecules. Such combinations allow the fabrication of highly sensitive, reproducible, stable and recyclable SERS substrates. The present article focusses on new developments in design and engineering of such recyclable SERS substrates. The recyclable SERS substrates made of PNSs (Au or Ag NSs) and semiconductor photocatalyst (metal oxides; TiO2, ZnO, WO3, Fe3O4, and others; CdS, conducting polymers, Si NSs) NSs are mainly discussed along with fundamental mechanisms of their multifunctional actions. These recyclable SERS substrates are potential candidates for the detection and elimination of organic compounds (pollutants) as discussed in detail with special emphasis on their reproducibility and long term stability. In addition, current challenges and future potential requirements are also discussed.
{"title":"Fundamentals and applications of recyclable SERS substrates","authors":"J. Prakash","doi":"10.1080/0144235X.2019.1660114","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1660114","url":null,"abstract":"ABSTRACT Surface enhanced Raman scattering (SERS) substrates, composed of plasmonic nanostructures (PNSs) and photocatalyst semiconductors, have emerged as novel multifunctional nanomaterials for advanced engineering applications. These combinations improve the photocatalytic activity of such systems and extend their application as recyclable SERS substrates owing to their self-cleaning ability by photodegradation of analyte molecules. Such combinations allow the fabrication of highly sensitive, reproducible, stable and recyclable SERS substrates. The present article focusses on new developments in design and engineering of such recyclable SERS substrates. The recyclable SERS substrates made of PNSs (Au or Ag NSs) and semiconductor photocatalyst (metal oxides; TiO2, ZnO, WO3, Fe3O4, and others; CdS, conducting polymers, Si NSs) NSs are mainly discussed along with fundamental mechanisms of their multifunctional actions. These recyclable SERS substrates are potential candidates for the detection and elimination of organic compounds (pollutants) as discussed in detail with special emphasis on their reproducibility and long term stability. In addition, current challenges and future potential requirements are also discussed.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2019-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82795460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-03DOI: 10.1080/0144235X.2019.1634319
Xiaohua Yang, Gaixia Zhang, J. Prakash, Zhangsen Chen, M. Gauthier, Shuhui Sun
ABSTRACT Graphene, one of the most promising two-dimensional (2D) nanomaterials, has gained substantial attention in several areas of materials science. Due to its unique mechanical, electrical, optical, and thermal properties, graphene-based materials have triggered both numerous fundamental studies and technological applications. Out of several synthetic methods, chemical vapour deposition (CVD) has emerged as one of the most promising methods for the production of large areas of high quality single-crystal graphene. This review introduces the fundamental growth mechanisms of CVD graphene, alongside the various parameters and substrates employed in this process. Furthermore, new developments in the CVD synthesis of monolayer and few-layer graphene are presented, as well as advanced techniques for analysing the fine structure and properties of graphene. Moreover, a detailed discussion of the transfer processes used for practical applications of CVD graphene is provided, with emphasis on their fundamental aspects. This review concludes with an outlook on presently challenging issues, prospects and applications of graphene.
{"title":"Chemical vapour deposition of graphene: layer control, the transfer process, characterisation, and related applications","authors":"Xiaohua Yang, Gaixia Zhang, J. Prakash, Zhangsen Chen, M. Gauthier, Shuhui Sun","doi":"10.1080/0144235X.2019.1634319","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1634319","url":null,"abstract":"ABSTRACT Graphene, one of the most promising two-dimensional (2D) nanomaterials, has gained substantial attention in several areas of materials science. Due to its unique mechanical, electrical, optical, and thermal properties, graphene-based materials have triggered both numerous fundamental studies and technological applications. Out of several synthetic methods, chemical vapour deposition (CVD) has emerged as one of the most promising methods for the production of large areas of high quality single-crystal graphene. This review introduces the fundamental growth mechanisms of CVD graphene, alongside the various parameters and substrates employed in this process. Furthermore, new developments in the CVD synthesis of monolayer and few-layer graphene are presented, as well as advanced techniques for analysing the fine structure and properties of graphene. Moreover, a detailed discussion of the transfer processes used for practical applications of CVD graphene is provided, with emphasis on their fundamental aspects. This review concludes with an outlook on presently challenging issues, prospects and applications of graphene.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2019-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80540616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-01-02DOI: 10.1080/0144235X.2019.1608689
A. S. Hansen, Emil Vogt, H. Kjaergaard
ABSTRACT Formation and growth of atmospheric aerosols are governed by the Gibbs energy of complex formation (). A number of hydrogen bound bimolecular complexes in the gas phase at room temperature have been detected. In this review, we illustrate how can be determined by combining gas phase infrared spectroscopy and vibrational theory. The XH-stretching (where X is a heavy atom like O) fundamental transition of the hydrogen bond donor molecule in the complex is redshifted and its intensity enhanced upon complexation. This facilitates detection of weak complexes even though the equilibrium is shifted towards the monomers at room temperature. The ratio of the measured and calculated intensity of the vibrational transition is proportional to the complex abundance, which with known monomer pressures gives the equilibrium constant and thus . This approach relies on calculated vibrational transitions in the complexes. An accurate description of the observed bound XH-stretching fundamental transition is challenging due to effects of the low-frequency intermolecular modes. We have developed reduced dimensionality vibrational models within the local mode picture to calculate accurate vibrational intensities. For complexes with an alcohol donor molecule, we find that P, O or S as the acceptor atom of the hydrogen bond results in very similar hydrogen bond strength, whereas N provides a significantly stronger bond.
{"title":"Gibbs energy of complex formation – combining infrared spectroscopy and vibrational theory","authors":"A. S. Hansen, Emil Vogt, H. Kjaergaard","doi":"10.1080/0144235X.2019.1608689","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1608689","url":null,"abstract":"ABSTRACT Formation and growth of atmospheric aerosols are governed by the Gibbs energy of complex formation (). A number of hydrogen bound bimolecular complexes in the gas phase at room temperature have been detected. In this review, we illustrate how can be determined by combining gas phase infrared spectroscopy and vibrational theory. The XH-stretching (where X is a heavy atom like O) fundamental transition of the hydrogen bond donor molecule in the complex is redshifted and its intensity enhanced upon complexation. This facilitates detection of weak complexes even though the equilibrium is shifted towards the monomers at room temperature. The ratio of the measured and calculated intensity of the vibrational transition is proportional to the complex abundance, which with known monomer pressures gives the equilibrium constant and thus . This approach relies on calculated vibrational transitions in the complexes. An accurate description of the observed bound XH-stretching fundamental transition is challenging due to effects of the low-frequency intermolecular modes. We have developed reduced dimensionality vibrational models within the local mode picture to calculate accurate vibrational intensities. For complexes with an alcohol donor molecule, we find that P, O or S as the acceptor atom of the hydrogen bond results in very similar hydrogen bond strength, whereas N provides a significantly stronger bond.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2019-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88900687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-01-02DOI: 10.1080/0144235X.2019.1593583
S. V. Krasnoshchekov, Xuanhao Chang
ABSTRACT Quantum-mechanical methods of solving the polyatomic vibrational Schrödinger equation need higher quality zero-order approximations than ones originating from the harmonic oscillator (HO). Ladder operators built on the HO have a number of unique features simplifying both the operator perturbation theory and practical implementations of matrix-elements-based methods. Therefore, finding suitable ladder operators for solvable anharmonic oscillators and mainly the Morse oscillator remain one of the major challenges of nuclear vibrational dynamics. In this work, we review the problem of building Morse oscillator ladder operators (MLOs) and the prospects of their use in various methods of solving the many-dimensional anharmonic vibrational problem. The features of several existing approaches for building MLOs are explored and analysed. The native MLOs obtained by the factorisation method are not quite suitable for expressing a perturbed potential energy operator. Supersymmetric quantum mechanics (SUSYQM) does not solve the problem either since corresponding ladder operators only connect states from related potentials. The SU(2) vibron model provides an approximate solution based on a formal isomorphism of energy states. We have found that for the present the only useful model for MLOs is based on the so-called quasi-number states basis set (QNSB) built on modified Laguerre polynomials. QNSB yields a finite tridiagonal matrix representation of the Morse Hamiltonian corresponding to the exact solution. The convenience and accuracy of QNSB approach in comparison to second/fourth-order perturbation theory is illustrated with the HF molecule. The general conclusion is that QNSB-based MLOs are suitable for building many-body treatments, for instance, with the VSCF/VCI approach.
{"title":"Ladder operators for Morse oscillator and a perturbed vibrational problem","authors":"S. V. Krasnoshchekov, Xuanhao Chang","doi":"10.1080/0144235X.2019.1593583","DOIUrl":"https://doi.org/10.1080/0144235X.2019.1593583","url":null,"abstract":"ABSTRACT Quantum-mechanical methods of solving the polyatomic vibrational Schrödinger equation need higher quality zero-order approximations than ones originating from the harmonic oscillator (HO). Ladder operators built on the HO have a number of unique features simplifying both the operator perturbation theory and practical implementations of matrix-elements-based methods. Therefore, finding suitable ladder operators for solvable anharmonic oscillators and mainly the Morse oscillator remain one of the major challenges of nuclear vibrational dynamics. In this work, we review the problem of building Morse oscillator ladder operators (MLOs) and the prospects of their use in various methods of solving the many-dimensional anharmonic vibrational problem. The features of several existing approaches for building MLOs are explored and analysed. The native MLOs obtained by the factorisation method are not quite suitable for expressing a perturbed potential energy operator. Supersymmetric quantum mechanics (SUSYQM) does not solve the problem either since corresponding ladder operators only connect states from related potentials. The SU(2) vibron model provides an approximate solution based on a formal isomorphism of energy states. We have found that for the present the only useful model for MLOs is based on the so-called quasi-number states basis set (QNSB) built on modified Laguerre polynomials. QNSB yields a finite tridiagonal matrix representation of the Morse Hamiltonian corresponding to the exact solution. The convenience and accuracy of QNSB approach in comparison to second/fourth-order perturbation theory is illustrated with the HF molecule. The general conclusion is that QNSB-based MLOs are suitable for building many-body treatments, for instance, with the VSCF/VCI approach.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2019-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90574579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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