Pub Date : 2021-07-03DOI: 10.1080/0144235X.2021.1952006
N. Shafizadeh, M. Crestoni, A. de la Lande, B. Soep
This review summarizes the state-of-the-art knowledge of heme ligation in the gas phase. The unique aspect of the gas phase approach is to allow a step-by-step ligation of heme and thus enables the analysis of the properties of -four, -five and -six coordinate hemes in vacuo, under conditions directly comparable with quantum calculations. This approach also allows the characterization of situations uncommon in Nature, completing the coordination spectrum of hemes: four coordinate heme and protonated heme, an intermediate between ferrous and ferric heme. Therefore, a complete set of systems is described for the ferrous and ferric cases and there is no discontinuity between the two oxidation states of iron, so that the same mechanisms are at work, donation and back donation of different strengths depending upon the ligand. The similarity of ligation properties in ferrous and ferric hemes is consistent with calculations of the electron density at the Fe atom level, rather independent of the formal oxidation state in contrast with the porphyrin cycle. Hemes spin states have been reviewed, for they identify the electronic distribution of the metal. In ligated ferrous and ferric hemes, we find that binding energy measurements combined with spectroscopy describe their properties most effectively.
{"title":"Heme ligation in the gas phase","authors":"N. Shafizadeh, M. Crestoni, A. de la Lande, B. Soep","doi":"10.1080/0144235X.2021.1952006","DOIUrl":"https://doi.org/10.1080/0144235X.2021.1952006","url":null,"abstract":"This review summarizes the state-of-the-art knowledge of heme ligation in the gas phase. The unique aspect of the gas phase approach is to allow a step-by-step ligation of heme and thus enables the analysis of the properties of -four, -five and -six coordinate hemes in vacuo, under conditions directly comparable with quantum calculations. This approach also allows the characterization of situations uncommon in Nature, completing the coordination spectrum of hemes: four coordinate heme and protonated heme, an intermediate between ferrous and ferric heme. Therefore, a complete set of systems is described for the ferrous and ferric cases and there is no discontinuity between the two oxidation states of iron, so that the same mechanisms are at work, donation and back donation of different strengths depending upon the ligand. The similarity of ligation properties in ferrous and ferric hemes is consistent with calculations of the electron density at the Fe atom level, rather independent of the formal oxidation state in contrast with the porphyrin cycle. Hemes spin states have been reviewed, for they identify the electronic distribution of the metal. In ligated ferrous and ferric hemes, we find that binding energy measurements combined with spectroscopy describe their properties most effectively.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80269686","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 : 2021-04-03DOI: 10.1080/0144235X.2021.1918498
A. Potapov, M. McCoustra
Dust grains play a central role in the physics and chemistry of cosmic environments. They influence the optical and thermal properties of the medium due to their interaction with stellar radiation; provide surfaces for the chemical reactions that are responsible for the synthesis of a significant fraction of key astronomical molecules; and they are building blocks of pebbles, comets, asteroids, planetesimals, and planets. In this paper, we review experimental studies of physical and chemical processes, such as adsorption, desorption, diffusion and reactions forming molecules, on the surface of reliable cosmic dust grain analogues as related to processes in diffuse, translucent, and dense interstellar clouds, protostellar envelopes, planet-forming disks, and planetary atmospheres. The information that such experiments reveal should be flexible enough to be used in many different environments. In addition, we provide a forward look discussing new ideas, experimental approaches, and research directions.
{"title":"Physics and chemistry on the surface of cosmic dust grains: a laboratory view","authors":"A. Potapov, M. McCoustra","doi":"10.1080/0144235X.2021.1918498","DOIUrl":"https://doi.org/10.1080/0144235X.2021.1918498","url":null,"abstract":"Dust grains play a central role in the physics and chemistry of cosmic environments. They influence the optical and thermal properties of the medium due to their interaction with stellar radiation; provide surfaces for the chemical reactions that are responsible for the synthesis of a significant fraction of key astronomical molecules; and they are building blocks of pebbles, comets, asteroids, planetesimals, and planets. In this paper, we review experimental studies of physical and chemical processes, such as adsorption, desorption, diffusion and reactions forming molecules, on the surface of reliable cosmic dust grain analogues as related to processes in diffuse, translucent, and dense interstellar clouds, protostellar envelopes, planet-forming disks, and planetary atmospheres. The information that such experiments reveal should be flexible enough to be used in many different environments. In addition, we provide a forward look discussing new ideas, experimental approaches, and research directions.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79306789","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 : 2021-04-03DOI: 10.1080/0144235X.2021.1874118
Ketan Sharma, T. Miller, J. Stanton
The interaction of electronic and nuclear motion – broadly categorised as ‘vibronic coupling’ – plays a number of roles in areas that range from molecular dynamics to electronic spectroscopy. Additionally, these phenomena pose significant challenges to both computational electronic spectroscopy and quantum chemistry, as the usual approximations (Franck–Condon and Born–Oppenheimer) are often rendered unsatisfactory. After beginning with a broad overview of vibronic coupling effects and some computational strategies for characterising them, the review discusses how these effects are manifested in various types of spectra. Particular emphasis is given to fine-structure effects in Jahn–Teller systems that arise from couplings involving rotational, orbital and spin angular momenta. Unlike overall vibronic level structure, which has been quite well studied both theoretically and experimentally, these more subtle effects are seen only at high (rotationally-resolved) resolution, and are less well understood. The review gives a detailed description of the quantum-mechanical origin of these splittings and provides some computational strategies for predicting them. A broad overview is given of families of Jahn–Teller active molecules that have been investigated experimentally and theoretically. Detailed discussion is given for two JT-active radicals where theory and experiment are compared at both low and high resolution: cyclopentadienyl (C H ) and methoxy (CH O).
{"title":"Vibronically coupled states: computational considerations and characterisation of vibronic and rovibronic spectroscopic parameters","authors":"Ketan Sharma, T. Miller, J. Stanton","doi":"10.1080/0144235X.2021.1874118","DOIUrl":"https://doi.org/10.1080/0144235X.2021.1874118","url":null,"abstract":"The interaction of electronic and nuclear motion – broadly categorised as ‘vibronic coupling’ – plays a number of roles in areas that range from molecular dynamics to electronic spectroscopy. Additionally, these phenomena pose significant challenges to both computational electronic spectroscopy and quantum chemistry, as the usual approximations (Franck–Condon and Born–Oppenheimer) are often rendered unsatisfactory. After beginning with a broad overview of vibronic coupling effects and some computational strategies for characterising them, the review discusses how these effects are manifested in various types of spectra. Particular emphasis is given to fine-structure effects in Jahn–Teller systems that arise from couplings involving rotational, orbital and spin angular momenta. Unlike overall vibronic level structure, which has been quite well studied both theoretically and experimentally, these more subtle effects are seen only at high (rotationally-resolved) resolution, and are less well understood. The review gives a detailed description of the quantum-mechanical origin of these splittings and provides some computational strategies for predicting them. A broad overview is given of families of Jahn–Teller active molecules that have been investigated experimentally and theoretically. Detailed discussion is given for two JT-active radicals where theory and experiment are compared at both low and high resolution: cyclopentadienyl (C H ) and methoxy (CH O).","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74693927","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 : 2020-11-30DOI: 10.1080/0144235X.2021.1838805
P. Deshmukh, Sourav Banerjee
It is remarkable that time delay is an experimentally measurable quantity, but time itself is not. Time delay in quantum collisions and in photoionisation/photodetachment of atomic and molecular systems is reviewed in this paper. Wigner–Eisenbud formalism of time delay in quantum collision of a wavepacket with a target is discussed. Its equivalence with Smith's formalism of time delay, based on an independent basis for time delay in terms of excess particle density in the collision zone, is demonstrated. Similarity and difference between quantum collision of an electron with a positive atomic/molecular ion and photoionisation/photodetachment of a neutral atom/molecule are discussed, and the underlying quantum dynamics involving the time-reversal symmetry between solutions with outgoing and ingoing wave boundary conditions is pointed out to interpret photoionisation/photodetachment as half-scattering. This relationship is subsequently taken advantage to extend the formalism of Wigner–Eisenbud–Smith time delay in photoionisation/photodetachment. The measurability of time delay is accounted for in terms of a self-adjoint quantum operator that characterises it, even if there is no such operator for time itself. A few illustrative examples of theoretical and experimental studies of time delay are given to indicate outstanding advances made in this field in the last two decades.
{"title":"Time delay in atomic and molecular collisions and photoionisation/photodetachment","authors":"P. Deshmukh, Sourav Banerjee","doi":"10.1080/0144235X.2021.1838805","DOIUrl":"https://doi.org/10.1080/0144235X.2021.1838805","url":null,"abstract":"It is remarkable that time delay is an experimentally measurable quantity, but time itself is not. Time delay in quantum collisions and in photoionisation/photodetachment of atomic and molecular systems is reviewed in this paper. Wigner–Eisenbud formalism of time delay in quantum collision of a wavepacket with a target is discussed. Its equivalence with Smith's formalism of time delay, based on an independent basis for time delay in terms of excess particle density in the collision zone, is demonstrated. Similarity and difference between quantum collision of an electron with a positive atomic/molecular ion and photoionisation/photodetachment of a neutral atom/molecule are discussed, and the underlying quantum dynamics involving the time-reversal symmetry between solutions with outgoing and ingoing wave boundary conditions is pointed out to interpret photoionisation/photodetachment as half-scattering. This relationship is subsequently taken advantage to extend the formalism of Wigner–Eisenbud–Smith time delay in photoionisation/photodetachment. The measurability of time delay is accounted for in terms of a self-adjoint quantum operator that characterises it, even if there is no such operator for time itself. A few illustrative examples of theoretical and experimental studies of time delay are given to indicate outstanding advances made in this field in the last two decades.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86709855","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 : 2020-10-21DOI: 10.1080/0144235X.2020.1823168
Michael Werther, Sreeja Loho Choudhury, F. Grossmann
In this review, we give a comprehensive comparison of the most widely used coherent state (CS) based methods to solve the time-dependent Schrödinger equation (TDSE). Starting from the fully variational coherent states (VCS) method, after a first approximation, the coupled coherent states (CCS) method can be derived, whereas an additional approximation leads to the semiclassical Herman–Kluk (HK) method. We numerically compare the different methods with another one, based on a static rectangular grid of coherent states (SCS), by applying all of them to the revival dynamics in a 1D Morse oscillator, with a special focus on the number of basis states (for the CCS and HK methods the number of classical trajectories) needed for convergence and the related issue of tight frames, which in principle allow the usage of CSs as if they were orthogonal. Different discretisation strategies for the occurring phase space integrals for systems with more degrees of freedom are also discussed and the apoptosis procedure that allows to circumvent the linear dependency problem in the VCS method is reviewed. The Holstein molecular crystal model serves to further illustrate the latter point.
{"title":"Coherent state based solutions of the time-dependent Schrödinger equation: hierarchy of approximations to the variational principle","authors":"Michael Werther, Sreeja Loho Choudhury, F. Grossmann","doi":"10.1080/0144235X.2020.1823168","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1823168","url":null,"abstract":"In this review, we give a comprehensive comparison of the most widely used coherent state (CS) based methods to solve the time-dependent Schrödinger equation (TDSE). Starting from the fully variational coherent states (VCS) method, after a first approximation, the coupled coherent states (CCS) method can be derived, whereas an additional approximation leads to the semiclassical Herman–Kluk (HK) method. We numerically compare the different methods with another one, based on a static rectangular grid of coherent states (SCS), by applying all of them to the revival dynamics in a 1D Morse oscillator, with a special focus on the number of basis states (for the CCS and HK methods the number of classical trajectories) needed for convergence and the related issue of tight frames, which in principle allow the usage of CSs as if they were orthogonal. Different discretisation strategies for the occurring phase space integrals for systems with more degrees of freedom are also discussed and the apoptosis procedure that allows to circumvent the linear dependency problem in the VCS method is reviewed. The Holstein molecular crystal model serves to further illustrate the latter point.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73433418","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 : 2020-10-15DOI: 10.1080/0144235X.2020.1823167
Aurora Rodríguez-Rodríguez, M. Zaiss, David Esteban-Gómez, G. Angelovski, C. Platas‐Iglesias
Magnetic resonance imaging (MRI) has emerged as very important tool in biomedical research and is an essential diagnostic method in clinical radiology today. Lately, chemical exchange saturation transfer (CEST) has become a very attractive alternative to the classical MRI methodologies. CEST uses a unique operating mechanism to generate contrast and possesses great potential for functional imaging investigations, especially in combination with diamagnetic and paramagnetic (dia- and paraCEST, respectively) contrast agents. However, CEST is governed by a combination of several parameters that together influence the overall intensity of observed CEST effect. The understanding of the physics of CEST has advanced significantly to provide a reliable assessment on contribution of individual parameters important for generation of a CEST signal. Nevertheless, there seem to be a missing link between the above mentioned theory and its practical application, especially in the development of new probes. This review article provides background information on CEST and paraCEST, analyzing the importance of the main physical parameters, such as exchange rate, saturation power and time, or paramagnetic shift and relaxation times. We describe the different types of paramagnetic complexes based on lanthanide or transition metal ions, and discuss their properties in the context of potential CEST application.
{"title":"Paramagnetic chemical exchange saturation transfer agents and their perspectives for application in magnetic resonance imaging","authors":"Aurora Rodríguez-Rodríguez, M. Zaiss, David Esteban-Gómez, G. Angelovski, C. Platas‐Iglesias","doi":"10.1080/0144235X.2020.1823167","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1823167","url":null,"abstract":"Magnetic resonance imaging (MRI) has emerged as very important tool in biomedical research and is an essential diagnostic method in clinical radiology today. Lately, chemical exchange saturation transfer (CEST) has become a very attractive alternative to the classical MRI methodologies. CEST uses a unique operating mechanism to generate contrast and possesses great potential for functional imaging investigations, especially in combination with diamagnetic and paramagnetic (dia- and paraCEST, respectively) contrast agents. However, CEST is governed by a combination of several parameters that together influence the overall intensity of observed CEST effect. The understanding of the physics of CEST has advanced significantly to provide a reliable assessment on contribution of individual parameters important for generation of a CEST signal. Nevertheless, there seem to be a missing link between the above mentioned theory and its practical application, especially in the development of new probes. This review article provides background information on CEST and paraCEST, analyzing the importance of the main physical parameters, such as exchange rate, saturation power and time, or paramagnetic shift and relaxation times. We describe the different types of paramagnetic complexes based on lanthanide or transition metal ions, and discuss their properties in the context of potential CEST application.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90574282","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 : 2020-10-09DOI: 10.1080/0144235X.2020.1822590
K. Lin, Balaganesh Muthiah, Hsiu-Pu Chang, T. Kasai, Yuan‐Pin Chang
Atomic halogen elimination from halogen-related compounds plays a vital role in the depletion of the ozone layer and is well investigated. However, the probabilities for elimination of molecular halogens and hydrogen halides are rarely scrutinised. We develop distinct method for the investigation of each kind of fragment. Velocity-mapping ion-imaging was employed to study the atomic halogen elimination from alkyl halides and aryl halides, focusing on the fractions of the translational energy release, the quantum yields of the atomic fragments, transition probability for curve crossing, competitive halogen-related bond fission, and anisotropy parameters to understand their dynamical complexity. Cavity ring-down absorption spectroscopy was implemented to investigate the molecular halogen fragments dissociated from the aliphatic halides and acyl halides for their optical spectra, vibrational branches, quantum yields, and the dissociation mechanisms. Time-resolved Fourier transform infrared emission spectroscopy was employed to confine the primary products of hydrogen halide elimination from acyl halides in the presence of Ar gas. It is, for the first time, to overview these existing small halogen-related fragments eliminated from halogen-containing compounds. The detailed characterisation of these fragments should unveil complicated halogen-related dissociation mechanisms which may supplement the current knowledge and help with the photochemical assessment of halogen-related environmental issue.
{"title":"Halogen-related photodissociation in atmosphere: characterisation of atomic halogen, molecular halogen, and hydrogen halide","authors":"K. Lin, Balaganesh Muthiah, Hsiu-Pu Chang, T. Kasai, Yuan‐Pin Chang","doi":"10.1080/0144235X.2020.1822590","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1822590","url":null,"abstract":"Atomic halogen elimination from halogen-related compounds plays a vital role in the depletion of the ozone layer and is well investigated. However, the probabilities for elimination of molecular halogens and hydrogen halides are rarely scrutinised. We develop distinct method for the investigation of each kind of fragment. Velocity-mapping ion-imaging was employed to study the atomic halogen elimination from alkyl halides and aryl halides, focusing on the fractions of the translational energy release, the quantum yields of the atomic fragments, transition probability for curve crossing, competitive halogen-related bond fission, and anisotropy parameters to understand their dynamical complexity. Cavity ring-down absorption spectroscopy was implemented to investigate the molecular halogen fragments dissociated from the aliphatic halides and acyl halides for their optical spectra, vibrational branches, quantum yields, and the dissociation mechanisms. Time-resolved Fourier transform infrared emission spectroscopy was employed to confine the primary products of hydrogen halide elimination from acyl halides in the presence of Ar gas. It is, for the first time, to overview these existing small halogen-related fragments eliminated from halogen-containing compounds. The detailed characterisation of these fragments should unveil complicated halogen-related dissociation mechanisms which may supplement the current knowledge and help with the photochemical assessment of halogen-related environmental issue.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78956399","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 : 2020-10-01DOI: 10.1080/0144235x.2020.1826708
Carlos Larriba-Andaluz, J. Prell
While existing ion mobility calculators are capable of feats as impressive as calculating collision cross sections (CCS) within a few per cent and within a very reasonable time, the simplifications assumed in their estimations precludes them from being more precise, potentially overreaching with respect to the interpretation of existing calculations. With ion mobility instrumentation progressively reaching resolutions of several hundreds to thousands (accuracy in the range of ∼0.1%), a more accurate theoretical description of gas-phase ion mobility becomes necessary to correctly interpret experimental state-of-the-art separations. This manuscript entails an effort to consolidate the most relevant theoretical work pertaining to ion mobility within the ‘free molecular’ regime, describing in detail the rationale for approximations up to the two-temperature theory, using both a momentum transfer approach as well as the solution to the moments of the Boltzmann equation for the ion. With knowledge of the existing deficiencies in the numerical methods, the manuscript provides a series of necessary additions in order to better simulate some of the separations observed experimentally due to second-order effects, namely, high field effects, dipole alignment, angular velocities and moments of inertia, potential interactions and inelastic collisions among others.
{"title":"Fundamentals of ion mobility in the free molecular regime. Interlacing the past, present and future of ion mobility calculations","authors":"Carlos Larriba-Andaluz, J. Prell","doi":"10.1080/0144235x.2020.1826708","DOIUrl":"https://doi.org/10.1080/0144235x.2020.1826708","url":null,"abstract":"While existing ion mobility calculators are capable of feats as impressive as calculating collision cross sections (CCS) within a few per cent and within a very reasonable time, the simplifications assumed in their estimations precludes them from being more precise, potentially overreaching with respect to the interpretation of existing calculations. With ion mobility instrumentation progressively reaching resolutions of several hundreds to thousands (accuracy in the range of ∼0.1%), a more accurate theoretical description of gas-phase ion mobility becomes necessary to correctly interpret experimental state-of-the-art separations. This manuscript entails an effort to consolidate the most relevant theoretical work pertaining to ion mobility within the ‘free molecular’ regime, describing in detail the rationale for approximations up to the two-temperature theory, using both a momentum transfer approach as well as the solution to the moments of the Boltzmann equation for the ion. With knowledge of the existing deficiencies in the numerical methods, the manuscript provides a series of necessary additions in order to better simulate some of the separations observed experimentally due to second-order effects, namely, high field effects, dipole alignment, angular velocities and moments of inertia, potential interactions and inelastic collisions among others.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79157776","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 : 2020-09-18DOI: 10.1080/0144235X.2020.1815389
M. Paterson, D. Townsend
We present an overview of experimental and theoretical investigations exploring the dynamical evolution of Rydberg-to-valence character in the electronically excited states of small polyatomic molecules. Time-resolved photoelectron imaging (TRPEI), in conjunction with high-level quantum chemistry calculations, permits detailed insight into the non-adiabatic processes operating in these systems and we review several case studies drawn from our own work in this area over the last few years. Electronically excited Rydberg states that develop significant valence character along specific molecular coordinates provide potentially important pathways for the rapid and efficient redistribution of excess energy following ultraviolet absorption. As such, there is considerable interest in developing better understanding of role of these states play within a broad range of different photochemical environments. A central theme of this review considers the way in which key energy – and angle-resolved observables in TRPEI measurements are influenced by different aspects of transitory Rydberg-to-valence behaviour. Several themes are discussed within a coherent narrative, drawing on experimental and theoretical findings in a selected series of small organic species containing nitrogen heteroatoms. Critically, many of the effects we highlight will also be generalisable to related studies interrogating non-adiabatic processes within a much broader range of molecular systems.
{"title":"Rydberg-to-valence evolution in excited state molecular dynamics","authors":"M. Paterson, D. Townsend","doi":"10.1080/0144235X.2020.1815389","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1815389","url":null,"abstract":"We present an overview of experimental and theoretical investigations exploring the dynamical evolution of Rydberg-to-valence character in the electronically excited states of small polyatomic molecules. Time-resolved photoelectron imaging (TRPEI), in conjunction with high-level quantum chemistry calculations, permits detailed insight into the non-adiabatic processes operating in these systems and we review several case studies drawn from our own work in this area over the last few years. Electronically excited Rydberg states that develop significant valence character along specific molecular coordinates provide potentially important pathways for the rapid and efficient redistribution of excess energy following ultraviolet absorption. As such, there is considerable interest in developing better understanding of role of these states play within a broad range of different photochemical environments. A central theme of this review considers the way in which key energy – and angle-resolved observables in TRPEI measurements are influenced by different aspects of transitory Rydberg-to-valence behaviour. Several themes are discussed within a coherent narrative, drawing on experimental and theoretical findings in a selected series of small organic species containing nitrogen heteroatoms. Critically, many of the effects we highlight will also be generalisable to related studies interrogating non-adiabatic processes within a much broader range of molecular systems.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78083543","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 : 2020-08-24DOI: 10.1080/0144235x.2020.1794585
T. González-Lezana, O. Echt, M. Gatchell, M. Bartolomei, J. Campos-Martínez, P. Scheier
We review the solvation of atomic, molecular or cluster ions in HNDs. After briefly discussing the properties of snowballs in bulk helium we consider experimental conditions for the efficient synthesis of charged, doped HNDs. We show that the cluster ions observed in conventional mass spectrometers originate from fission of highly charged HNDs. The ionization threshold of HNDs doped with alkalis reveals the minimum cluster size required for full immersion. The abundance distributions of He X ions frequently reveal local anomalies or magic numbers. We demonstrate that the abundance is approximately proportional to the evaporation energy. Observed and calculated magic numbers will be compiled, including data for ions solvated in molecular hydrogen. Alternative methods to forming He X that do not employ HNDs will be summarized. Electronic excitation spectra of C and polycyclic aromatic hydrocarbon ions reveal the properties of the helium adsorption layer in quantitative detail. Next we discuss theoretical efforts to describe the interaction between ions and helium. We close with summarizing the size dependence of physical quantities computed for atomic alkali and alkaline earth cations in helium, such as binding energy, superfluid fraction, structural order, radial density profiles, and the existence of first and higher solvation shells.
{"title":"Solvation of ions in helium","authors":"T. González-Lezana, O. Echt, M. Gatchell, M. Bartolomei, J. Campos-Martínez, P. Scheier","doi":"10.1080/0144235x.2020.1794585","DOIUrl":"https://doi.org/10.1080/0144235x.2020.1794585","url":null,"abstract":"We review the solvation of atomic, molecular or cluster ions in HNDs. After briefly discussing the properties of snowballs in bulk helium we consider experimental conditions for the efficient synthesis of charged, doped HNDs. We show that the cluster ions observed in conventional mass spectrometers originate from fission of highly charged HNDs. The ionization threshold of HNDs doped with alkalis reveals the minimum cluster size required for full immersion. The abundance distributions of He X ions frequently reveal local anomalies or magic numbers. We demonstrate that the abundance is approximately proportional to the evaporation energy. Observed and calculated magic numbers will be compiled, including data for ions solvated in molecular hydrogen. Alternative methods to forming He X that do not employ HNDs will be summarized. Electronic excitation spectra of C and polycyclic aromatic hydrocarbon ions reveal the properties of the helium adsorption layer in quantitative detail. Next we discuss theoretical efforts to describe the interaction between ions and helium. We close with summarizing the size dependence of physical quantities computed for atomic alkali and alkaline earth cations in helium, such as binding energy, superfluid fraction, structural order, radial density profiles, and the existence of first and higher solvation shells.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73998536","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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