Pub Date : 2022-06-01DOI: 10.1063/1674-0068/cjcp2205089
Cong Wang, Lihan Zhang, Jian Liu, J. Shao
The imaginary time path integral formalism offers a powerful numerical tool for simulating thermodynamic properties of realistic systems. We show that, when second-order and fourth-order decompositions are employed, they share a remarkable unified analytic form for the partition function of the harmonic oscillator. We are then able to obtain the expression of the thermodynamic property and the leading error terms as well. In order to obtain reasonably optimal values of the free parameters in the generalized symmetric fourth-order decomposition scheme, we eliminate the leading error terms to achieve the accuracy of desired order for the thermodynamic property of the harmonic system. Such a strategy leads to an efficient fourth-order decomposition that produces third-order accurate thermodynamic properties for general systems.
{"title":"Generalized fourth-order decompositions of imaginary time path integral: Implications of the harmonic oscillator","authors":"Cong Wang, Lihan Zhang, Jian Liu, J. Shao","doi":"10.1063/1674-0068/cjcp2205089","DOIUrl":"https://doi.org/10.1063/1674-0068/cjcp2205089","url":null,"abstract":"The imaginary time path integral formalism offers a powerful numerical tool for simulating thermodynamic properties of realistic systems. We show that, when second-order and fourth-order decompositions are employed, they share a remarkable unified analytic form for the partition function of the harmonic oscillator. We are then able to obtain the expression of the thermodynamic property and the leading error terms as well. In order to obtain reasonably optimal values of the free parameters in the generalized symmetric fourth-order decomposition scheme, we eliminate the leading error terms to achieve the accuracy of desired order for the thermodynamic property of the harmonic system. Such a strategy leads to an efficient fourth-order decomposition that produces third-order accurate thermodynamic properties for general systems.","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48021392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-01DOI: 10.1063/1674-0068/cjcp2109163
Binbin Xie, Ke Wang, Pei-Ke Jia, Xiangxuan Liu, G. Cui
Excited-state double proton transfer (ESDPT) is a controversial issue which has long been plagued with theoretical and experimental communities. Herein, we took 1,8-dihydroxy-2-naphthaldehyde (DHNA) as a prototype and used combined complete active space self-consistent field (CASSCF) and multi-state complete active-space second-order perturbation (MS-CASPT2) methods to investigate ES-DPT and excited-state deactivation pathways of DHNA. Three different tautomer minima of S1-ENOL, S1-KETO-1, and S1-KETO-2 and two crucial conical intersections of S1S0-KETO-1 and S1S0-KETO-2 in.and between the S0 and S1 states were obtained. S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands. In addition, two-dimensional potential energy surfaces (2D-PESs) and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism. Specifically, the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless, whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca. 6.0 kcal/mol. The linear interpolated internal coordinate path connecting S1-KETO-1 (S1-KETO-2) and S1S0-KETO-1 (S1S0-KETO-2) is uphill with a barrier of ca. 12.0 kcal/mol, which will trap DHNA in the S1 state while therefore enabling dual-emission bands. On the other hand, the S1/S0 conical intersections would also prompt the S1 system to decay to the S0 state, which could be to certain extent suppressed by locking the rotation of the C5−C8−C9−O10 dihedral angle. These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.
{"title":"Excited-state double proton transfer of 1,8-dihydroxy-2-naphthaldehyde: A MS-CASPT2//CASSCF study","authors":"Binbin Xie, Ke Wang, Pei-Ke Jia, Xiangxuan Liu, G. Cui","doi":"10.1063/1674-0068/cjcp2109163","DOIUrl":"https://doi.org/10.1063/1674-0068/cjcp2109163","url":null,"abstract":"Excited-state double proton transfer (ESDPT) is a controversial issue which has long been plagued with theoretical and experimental communities. Herein, we took 1,8-dihydroxy-2-naphthaldehyde (DHNA) as a prototype and used combined complete active space self-consistent field (CASSCF) and multi-state complete active-space second-order perturbation (MS-CASPT2) methods to investigate ES-DPT and excited-state deactivation pathways of DHNA. Three different tautomer minima of S1-ENOL, S1-KETO-1, and S1-KETO-2 and two crucial conical intersections of S1S0-KETO-1 and S1S0-KETO-2 in.and between the S0 and S1 states were obtained. S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands. In addition, two-dimensional potential energy surfaces (2D-PESs) and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism. Specifically, the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless, whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca. 6.0 kcal/mol. The linear interpolated internal coordinate path connecting S1-KETO-1 (S1-KETO-2) and S1S0-KETO-1 (S1S0-KETO-2) is uphill with a barrier of ca. 12.0 kcal/mol, which will trap DHNA in the S1 state while therefore enabling dual-emission bands. On the other hand, the S1/S0 conical intersections would also prompt the S1 system to decay to the S0 state, which could be to certain extent suppressed by locking the rotation of the C5−C8−C9−O10 dihedral angle. These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":"1 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58525722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-01DOI: 10.1063/1674-0068/cjcp2203039
Yanfang Ji, Quansong Li
Based on the boron-containing thermally activated delayed fluorescence (TADF) compound p-AC (AC: acridine) 5,9-dioxa-13b-boranaphtho [3,2,1-de] anthracene (a), a series of new TADF molecules b1−b4 were designed via adding two nitrogen atoms at the AC donor part. Density functional theory and time-dependent density functional theory calculations were performed on the frontier orbital energy levels, emission spectra, singlet-triplet states energy gaps (Δ EST), reverse intersystem crossing (RISC) rate constant ( kRISC) for compounds a and b1−b4. Our calculation results show that the maximum emission wavelengths of b1−b4 are significantly blue-shifted by 47−125 nm compared with that of a. Molecules b1 and b3 exhibit dark-blue emission, while molecules b2 and b4 display light-blue emission, indicating that these four derivatives could be potential organic light-emitting diode (OLED) candidates with blue-light emitting. Moreover, we found the RISC processes in a, b2, and b4 can occur not only from T1 state to S1 state, but also from T2 state to S1 state significantly, while the RISC processes in b1 and b3 mainly take place via the T2→S1 hot exciton way. Importantly, the T1→S1 kRISC values of b2 and b4 are predicted to be two to three times of that of a, indicating enhanced TADF property. Our results not only provide two promising boron-based TADF candidates (b2 and b4), but also offer useful theoretical basis for the design of blue OLED materials.
{"title":"Boron-containing thermally activated delayed blue fluorescence materials via donor tuning: A theoretical study","authors":"Yanfang Ji, Quansong Li","doi":"10.1063/1674-0068/cjcp2203039","DOIUrl":"https://doi.org/10.1063/1674-0068/cjcp2203039","url":null,"abstract":"Based on the boron-containing thermally activated delayed fluorescence (TADF) compound p-AC (AC: acridine) 5,9-dioxa-13b-boranaphtho [3,2,1-de] anthracene (a), a series of new TADF molecules b1−b4 were designed via adding two nitrogen atoms at the AC donor part. Density functional theory and time-dependent density functional theory calculations were performed on the frontier orbital energy levels, emission spectra, singlet-triplet states energy gaps (Δ EST), reverse intersystem crossing (RISC) rate constant ( kRISC) for compounds a and b1−b4. Our calculation results show that the maximum emission wavelengths of b1−b4 are significantly blue-shifted by 47−125 nm compared with that of a. Molecules b1 and b3 exhibit dark-blue emission, while molecules b2 and b4 display light-blue emission, indicating that these four derivatives could be potential organic light-emitting diode (OLED) candidates with blue-light emitting. Moreover, we found the RISC processes in a, b2, and b4 can occur not only from T1 state to S1 state, but also from T2 state to S1 state significantly, while the RISC processes in b1 and b3 mainly take place via the T2→S1 hot exciton way. Importantly, the T1→S1 kRISC values of b2 and b4 are predicted to be two to three times of that of a, indicating enhanced TADF property. Our results not only provide two promising boron-based TADF candidates (b2 and b4), but also offer useful theoretical basis for the design of blue OLED materials.","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47838231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-28DOI: 10.1007/s11274-022-03281-w
María Celina Zabaloy, Marco Allegrini, Keren Hernandez Guijarro, Filipe Behrends Kraemer, Héctor Morrás, Leonardo Erijman
Glyphosate (N-(phosphonomethyl)glycine) has emerged as the top-selling herbicide worldwide because of its versatility in controlling annual and perennial weeds and the extensive use of glyphosate-resistant crops. Concerns related to the widespread use of glyphosate and its ubiquitous presence in the environment has led to a large number of studies and reviews, which examined the toxicity and fate of glyphosate and its major metabolite, aminomethylphosphonic acid (AMPA) in the environment. Because the biological breakdown of glyphosate is most likely the main elimination process, the biodegradation of glyphosate has also been the object of abundant experimental work. Importantly, glyphosate biodegradation in aquatic and soil ecosystems is affected not only by the composition and the activity of microbial communities, but also by the physical environment. However, the interplay between microbiomes and glyphosate biodegradation in edaphic and aquatic environments has rarely been considered before. The proposed minireview aims at filling this gap. We summarize the most recent work exploring glyphosate biodegradation in natural aquatic biofilms, the biological, chemical and physical factors and processes playing on the adsorption, transport and biodegradation of glyphosate at different levels of soil organization and under different agricultural managements, and its impact on soil microbial communities.
{"title":"Microbiomes and glyphosate biodegradation in edaphic and aquatic environments: recent issues and trends.","authors":"María Celina Zabaloy, Marco Allegrini, Keren Hernandez Guijarro, Filipe Behrends Kraemer, Héctor Morrás, Leonardo Erijman","doi":"10.1007/s11274-022-03281-w","DOIUrl":"10.1007/s11274-022-03281-w","url":null,"abstract":"<p><p>Glyphosate (N-(phosphonomethyl)glycine) has emerged as the top-selling herbicide worldwide because of its versatility in controlling annual and perennial weeds and the extensive use of glyphosate-resistant crops. Concerns related to the widespread use of glyphosate and its ubiquitous presence in the environment has led to a large number of studies and reviews, which examined the toxicity and fate of glyphosate and its major metabolite, aminomethylphosphonic acid (AMPA) in the environment. Because the biological breakdown of glyphosate is most likely the main elimination process, the biodegradation of glyphosate has also been the object of abundant experimental work. Importantly, glyphosate biodegradation in aquatic and soil ecosystems is affected not only by the composition and the activity of microbial communities, but also by the physical environment. However, the interplay between microbiomes and glyphosate biodegradation in edaphic and aquatic environments has rarely been considered before. The proposed minireview aims at filling this gap. We summarize the most recent work exploring glyphosate biodegradation in natural aquatic biofilms, the biological, chemical and physical factors and processes playing on the adsorption, transport and biodegradation of glyphosate at different levels of soil organization and under different agricultural managements, and its impact on soil microbial communities.</p>","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":"22 1","pages":"98"},"PeriodicalIF":0.0,"publicationDate":"2022-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82963383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-01DOI: 10.1063/1674-0068/cjcp2111230
A. Zhou, Zhiqiang Fu, X.-M. Cao, Yufen Zhao, Yong Wang
The divergent behavior of C−H bond oxidations of aliphatic substrates compared to those of aromatic substrates shown in Gupta's experiment was mechanistically studied herein by means of density functional theory calculations. Our calculations reveal that such difference is caused by different reaction mechanisms between two kinds of substrates (the aliphatic cyclohexane, 2,3-dimethylbutane and the aromatic toluene, ethylbenzene and cumene). For the aliphatic substrates, C−H oxidation by the oxidant FeV(O)(TAML) is a hydrogen atom transfer process; whereas for the aromatic substrates, C−H oxidation is a proton-coupled electron transfer (PCET) process with a proton transfer character on the transition state, that is, a proton-coupled electron transfer process holding a proton transfer-like transition state (PCET(PT)). This difference is caused by the strong π− π interactions between the tetra-anionic TAML ring and the phenyl ring of the aromatic substrates, which has a “pull” effect to make the electron transfer from substrates to the Fe=O moiety inefficient.
{"title":"A mechanistic switch in C−H bond activation by elusive FeV(O)(TAML) reaction intermediate: A theoretical study","authors":"A. Zhou, Zhiqiang Fu, X.-M. Cao, Yufen Zhao, Yong Wang","doi":"10.1063/1674-0068/cjcp2111230","DOIUrl":"https://doi.org/10.1063/1674-0068/cjcp2111230","url":null,"abstract":"The divergent behavior of C−H bond oxidations of aliphatic substrates compared to those of aromatic substrates shown in Gupta's experiment was mechanistically studied herein by means of density functional theory calculations. Our calculations reveal that such difference is caused by different reaction mechanisms between two kinds of substrates (the aliphatic cyclohexane, 2,3-dimethylbutane and the aromatic toluene, ethylbenzene and cumene). For the aliphatic substrates, C−H oxidation by the oxidant FeV(O)(TAML) is a hydrogen atom transfer process; whereas for the aromatic substrates, C−H oxidation is a proton-coupled electron transfer (PCET) process with a proton transfer character on the transition state, that is, a proton-coupled electron transfer process holding a proton transfer-like transition state (PCET(PT)). This difference is caused by the strong π− π interactions between the tetra-anionic TAML ring and the phenyl ring of the aromatic substrates, which has a “pull” effect to make the electron transfer from substrates to the Fe=O moiety inefficient.","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43874591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-01DOI: 10.1063/1674-0068/cjcp2110182
Sujun Ji, Zhiling Ding, Hang Yin, Daoyuan Zheng, Jin-feng Zhao
The interactions of complexes of XeOF2 and XeO3 with a series of different hybridization N-containing donors are studied by means of DFT and MP2 calculations. The aerogen bonding interaction energies range from 6.5 kcal/mol to 19.9 kcal/mol between XeO3 or XeOF2 and typical N-containing donors. The sequence of interaction for N-containing hybridization is sp3>sp2>sp, and XeO3 is higher than XeOF2. For some donors of sp2 and sp3 hybridization, the steric effect plays a minor role in the interaction with the evidence of reduced density gradient plots. The dominant stable part is the electrostatic interaction. In complex of XeO3, the weight of polarization is larger than dispersion, while the situation is opposite for XeOF2 complexes. Except for the sum of the maximum value of molecular electrostatic potential on Xe atom and minimum value of molecular electrostatic potential on N atom, the otherfive interaction parameters including the potential energy density at bond critical point, the equilibrium distances, interaction energies with the basis set superposition error correction, localized molecular orbital energy decomposition analysis interaction energies, and the electron charge density, show great linear correlation coefficients with each other.
{"title":"Theoretical study on Xe⋯N non-covalent interactions: Three hybridization N with XeO3 and XeOF2","authors":"Sujun Ji, Zhiling Ding, Hang Yin, Daoyuan Zheng, Jin-feng Zhao","doi":"10.1063/1674-0068/cjcp2110182","DOIUrl":"https://doi.org/10.1063/1674-0068/cjcp2110182","url":null,"abstract":"The interactions of complexes of XeOF2 and XeO3 with a series of different hybridization N-containing donors are studied by means of DFT and MP2 calculations. The aerogen bonding interaction energies range from 6.5 kcal/mol to 19.9 kcal/mol between XeO3 or XeOF2 and typical N-containing donors. The sequence of interaction for N-containing hybridization is sp3>sp2>sp, and XeO3 is higher than XeOF2. For some donors of sp2 and sp3 hybridization, the steric effect plays a minor role in the interaction with the evidence of reduced density gradient plots. The dominant stable part is the electrostatic interaction. In complex of XeO3, the weight of polarization is larger than dispersion, while the situation is opposite for XeOF2 complexes. Except for the sum of the maximum value of molecular electrostatic potential on Xe atom and minimum value of molecular electrostatic potential on N atom, the otherfive interaction parameters including the potential energy density at bond critical point, the equilibrium distances, interaction energies with the basis set superposition error correction, localized molecular orbital energy decomposition analysis interaction energies, and the electron charge density, show great linear correlation coefficients with each other.","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48891928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-01DOI: 10.1063/1674-0068/cjcp2110209
Hongling Zhang, Qingtong Liu, Yiying Wang, Zhe Tang, P. Zhou
Excited-state intramolecular proton transfer (ESIPT) is favored by researchers because of its unique optical properties. However, there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties. Therefore, we selected a series of benzoxazole isothiocyanate fluorescent dyes (2-HOB, 2-HSB, and 2-HSeB) by theoretical methods, and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms. The calculated bond angle, bond length, energy gap, and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB<2-HSB<2-HSeB. Correspondingly, the magnitude of the energy barrier of the potential energy curve is 2-HOB>2-HSB>2-HSeB. In addition, the calculated electronic spectrum shows that as the atomic electronegativity decreases, the emission spectrum has a redshift. Therefore, this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties.
{"title":"Regulation of excited-state intramolecular proton transfer process and photophysical properties for benzoxazole isothiocyanate fluorescent dyes by changing atomic electronegativity","authors":"Hongling Zhang, Qingtong Liu, Yiying Wang, Zhe Tang, P. Zhou","doi":"10.1063/1674-0068/cjcp2110209","DOIUrl":"https://doi.org/10.1063/1674-0068/cjcp2110209","url":null,"abstract":"Excited-state intramolecular proton transfer (ESIPT) is favored by researchers because of its unique optical properties. However, there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties. Therefore, we selected a series of benzoxazole isothiocyanate fluorescent dyes (2-HOB, 2-HSB, and 2-HSeB) by theoretical methods, and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms. The calculated bond angle, bond length, energy gap, and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB<2-HSB<2-HSeB. Correspondingly, the magnitude of the energy barrier of the potential energy curve is 2-HOB>2-HSB>2-HSeB. In addition, the calculated electronic spectrum shows that as the atomic electronegativity decreases, the emission spectrum has a redshift. Therefore, this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties.","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49179283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-01DOI: 10.1063/1674-0068/cjcp2109151
J. Gu, Zengjun Xiao, Chunting Yu, Qiang Zhang, Yang Chen, Dongfeng Zhao
Magnesium monofluoride (MgF) is proposed as an ideal candidate radical for direct laser cooling. Here, the rotationally resolved laser spectra of MgF for the A2Π− X2Σ+ electronic transition system were recorded by using laser induced fluorescence technique. The MgF radicals were produced by discharging SF6/Ar gas mixtures between the tips of two magnesium needles in a supersonic jet expansion. We recorded a total of 19 vibrational bands belonging to three sequences of Δ v=0, ±1 in the region of 348-370 nm. Accurate spectroscopic constants for both X2Σ+ and A2Π states are determined from rotational analysis of the experimental spectra. Spectroscopic parameters, including the Franck-Condon factors (FCFs), are determined from the experimental results and the Rydberg-Klein-Rees (RKR) calculations. Significant discrepancies between the experimentally measured and RKR-calculated FCFs are found, indicating that the FCFs are nearly independent of the spin-orbit coupling in the A2Π state. Potential energy curves (PECs) and FCFs determined here provide necessary data for the theoretical simulation of the laser-cooling scheme of MgF.
{"title":"High resolution laser excitation spectra and Franck-Condon factors of A2Π−X2Σ+ electronic transition of MgF","authors":"J. Gu, Zengjun Xiao, Chunting Yu, Qiang Zhang, Yang Chen, Dongfeng Zhao","doi":"10.1063/1674-0068/cjcp2109151","DOIUrl":"https://doi.org/10.1063/1674-0068/cjcp2109151","url":null,"abstract":"Magnesium monofluoride (MgF) is proposed as an ideal candidate radical for direct laser cooling. Here, the rotationally resolved laser spectra of MgF for the A2Π− X2Σ+ electronic transition system were recorded by using laser induced fluorescence technique. The MgF radicals were produced by discharging SF6/Ar gas mixtures between the tips of two magnesium needles in a supersonic jet expansion. We recorded a total of 19 vibrational bands belonging to three sequences of Δ v=0, ±1 in the region of 348-370 nm. Accurate spectroscopic constants for both X2Σ+ and A2Π states are determined from rotational analysis of the experimental spectra. Spectroscopic parameters, including the Franck-Condon factors (FCFs), are determined from the experimental results and the Rydberg-Klein-Rees (RKR) calculations. Significant discrepancies between the experimentally measured and RKR-calculated FCFs are found, indicating that the FCFs are nearly independent of the spin-orbit coupling in the A2Π state. Potential energy curves (PECs) and FCFs determined here provide necessary data for the theoretical simulation of the laser-cooling scheme of MgF.","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":" ","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48499846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-01DOI: 10.1063/1674-0068/cjcp2112286
Zi-Yu Li, Li-Hui Mou, G. Jiang, Qing-Yu Liu, Sheng‐Gui He
Adsorption and activation of dinitrogen (N2) is an indispensable process in nitrogen fixation. Metal nitride species continue to attract attention as a promising catalyst for ammonia synthesis. However, the detailed mechanisms at a molecular level between reactive nitride species and N2 remain unclear at elevated temperature, which is important to understand the temperature effect and narrow the gap between the gas phase system and condensed phase system. Herein, the 14N/15N isotopic exchange in the reaction between tantalum nitride cluster anions Ta314N3− and 15N2 leading to the regeneration of 14N2/14N15N was observed at elevated temperature (393−593 K) using mass spectrometry. With the aid of theoretical calculations, the exchange mechanism and the effect of temperature to promote the dissociation of N2 on Ta3N3− were elucidated. A comparison experiment for Ta314N4−/15N2 couple indicated that only desorption of 15N2 from Ta314N415N2− took place at elevated temperature. The different exchange behavior can be well understood by the fact that nitrogen vacancy is a requisite for the dinitrogen activation over metal nitride species. This study may shed light on understanding the role of nitrogen vacancy in nitride species for ammonia synthesis and provide clues in designing effective catalysts for nitrogen fixation.
{"title":"15 N/14N isotopic exchange in the dissociative adsorption of N2 on tantalum nitride cluster anions Ta3N3−","authors":"Zi-Yu Li, Li-Hui Mou, G. Jiang, Qing-Yu Liu, Sheng‐Gui He","doi":"10.1063/1674-0068/cjcp2112286","DOIUrl":"https://doi.org/10.1063/1674-0068/cjcp2112286","url":null,"abstract":"Adsorption and activation of dinitrogen (N2) is an indispensable process in nitrogen fixation. Metal nitride species continue to attract attention as a promising catalyst for ammonia synthesis. However, the detailed mechanisms at a molecular level between reactive nitride species and N2 remain unclear at elevated temperature, which is important to understand the temperature effect and narrow the gap between the gas phase system and condensed phase system. Herein, the 14N/15N isotopic exchange in the reaction between tantalum nitride cluster anions Ta314N3− and 15N2 leading to the regeneration of 14N2/14N15N was observed at elevated temperature (393−593 K) using mass spectrometry. With the aid of theoretical calculations, the exchange mechanism and the effect of temperature to promote the dissociation of N2 on Ta3N3− were elucidated. A comparison experiment for Ta314N4−/15N2 couple indicated that only desorption of 15N2 from Ta314N415N2− took place at elevated temperature. The different exchange behavior can be well understood by the fact that nitrogen vacancy is a requisite for the dinitrogen activation over metal nitride species. This study may shed light on understanding the role of nitrogen vacancy in nitride species for ammonia synthesis and provide clues in designing effective catalysts for nitrogen fixation.","PeriodicalId":10036,"journal":{"name":"Chinese Journal of Chemical Physics","volume":"1 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41360401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-01DOI: 10.1063/1674-0068/cjcp2111223
Wei Zhang, J. Kong, Wenqi Xu, Xinmiao Niu, D. Song, Weimin Liu, A. Xia
The symmetric and quadrupolar donor-acceptor-donor (D-A-D) molecules usually exhibit excited-state charge redistribution process from delocalized intramolecular charge transfer (ICT) state to localized ICT state. Direct observation of such charge redistribution process in real-time has been intensively studied via various ultrafast time-resolved spectroscopies. Femtosecond stimulated Raman spectroscopy (FSRS) is one of the powerful methods which can be used to determine the excited state dynamics by tracking vibrational mode evolution of the specific chemical bonds within molecules. Herein, a molecule, 4,4′-(buta-1,3-diyne-1,4-diyl)bis( N, N-bis(4-methoxyphenyl)aniline), that consists of two central adjacent alkyne (-C≡C-) groups as electron-acceptors and two separated, symmetric N, N-bis(4-methoxyphenyl)aniline at both branches as electron-donors, is chosen to investigate the excited-state photophysical properties. It is shown that the solvation induced excited-state charge redistribution in polar solvents can be probed by using femtosecond stimulated Raman spectroscopy. The results provide a fundamental understanding of photoexcitation induced charge delocalization/localization properties of the symmetric quadrupolar molecules with adjacent vibrational markers located at central position.
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