Pub Date : 2025-02-01DOI: 10.1016/j.jms.2025.111986
Greta Naso , Filippo Baroncelli , Luca Evangelisti , Assimo Maris , Sonia Melandri
The rotational spectrum of trifluoroacetic acid has been recorded at room temperature in the 18–26 GHz frequency range using a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. More than 180 new spectral lines have been identified and assigned to transitions within the vibrational ground state. A global fitting has been performed by incorporating spectroscopic data from previous studies, leading to the refinement of the molecular parameters. Two fitting models using Watson’s -reduction and -reduction are proposed, allowing the determination of for the first model and , , and for the second one.
{"title":"Rotational spectrum of trifluoroacetic acid: Extension of the measurements by chirped-pulse spectroscopy","authors":"Greta Naso , Filippo Baroncelli , Luca Evangelisti , Assimo Maris , Sonia Melandri","doi":"10.1016/j.jms.2025.111986","DOIUrl":"10.1016/j.jms.2025.111986","url":null,"abstract":"<div><div>The rotational spectrum of trifluoroacetic acid has been recorded at room temperature in the 18–26 GHz frequency range using a chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer. More than 180 new spectral lines have been identified and assigned to transitions within the vibrational ground state. A global fitting has been performed by incorporating spectroscopic data from previous studies, leading to the refinement of the molecular parameters. Two fitting models using Watson’s <span><math><mi>S</mi></math></span>-reduction and <span><math><mi>A</mi></math></span>-reduction are proposed, allowing the determination of <span><math><msub><mrow><mi>h</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> for the first model and <span><math><msub><mrow><mi>Φ</mi></mrow><mrow><mi>J</mi><mi>K</mi></mrow></msub></math></span>, <span><math><msub><mrow><mi>Φ</mi></mrow><mrow><mi>K</mi><mi>J</mi></mrow></msub></math></span>, and <span><math><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>K</mi></mrow></msub></math></span> for the second one.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"408 ","pages":"Article 111986"},"PeriodicalIF":1.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.jms.2025.111999
Kristin N. Bales , Dominik Kosican , Jack C. Harms , James J. O’Brien , Leah C. O’Brien
Two transitions of tungsten sulfide (WS) near 13,100 cm−1, the (0,0) band of the [13.10]1 –X3Σ−0+ transition and the (0,0) band of the [15.30]1 –X3Σ−1 transition, have been recorded at high resolution using intracavity laser absorption spectroscopy with a Fourier-transform spectrometer used for detection (ILS-FTS). The WS molecules were produced in the plasma discharge formed by applying 0.70–0.80 A of a discharge current from a pulsed DC plasma generator to a tungsten-lined copper hollow cathode. The reaction took place in the presence of Ar (∼70 %), H2 (∼30 %), and CS2 (∼0.1 %) gases at a total pressure of approximately 2 torr. Lines for all four abundant isotopologues of WS, 182W32S, 183W32S, 184W32S, and 186W32S, were measured and a rotational analysis was performed using PGOPHER. A constrained parameters approach was used to maintain expected mass relationships among isotopologues. This analysis increases the number of observed rotational levels from J ∼ 30 to J ∼ 100 for both excited states, allowing an increase in precision of spectroscopic constants. The new analysis of the [15.30]1 –X3Σ−(1) transition enabled the reduced uncertainty in the previously determined value for the splitting of the 0+ and 1 Ω-components of the X3Σ− ground state. Also presented in this work is an expansion upon our earlier deperturbation analysis involving the [15.30]1 state to include the v′ = 2 vibrational level, which is perturbed by the v′ = 4 vibrational level of the [14.26]0+ state.
{"title":"Rotational analyses of two transitions of WS near 13,100 cm−1, and further deperturbation analysis of the [15.30]1 – X 3Σ−0+ transition","authors":"Kristin N. Bales , Dominik Kosican , Jack C. Harms , James J. O’Brien , Leah C. O’Brien","doi":"10.1016/j.jms.2025.111999","DOIUrl":"10.1016/j.jms.2025.111999","url":null,"abstract":"<div><div>Two transitions of tungsten sulfide (WS) near 13,100 cm<sup>−1</sup>, the (0,0) band of the [13.10]1 <strong>–</strong> <em>X</em> <sup>3</sup>Σ<sup>−</sup><sub>0+</sub> transition and the (0,0) band of the [15.30]1 <strong>–</strong> <em>X</em> <sup>3</sup>Σ<sup>−</sup><sub>1</sub> transition, have been recorded at high resolution using intracavity laser absorption spectroscopy with a Fourier-transform spectrometer used for detection (ILS-FTS). The WS molecules were produced in the plasma discharge formed by applying 0.70–0.80 A of a discharge current from a pulsed DC plasma generator to a tungsten-lined copper hollow cathode. The reaction took place in the presence of Ar (∼70 %), H<sub>2</sub> (∼30 %), and CS<sub>2</sub> (∼0.1 %) gases at a total pressure of approximately 2 torr. Lines for all four abundant isotopologues of WS, <sup>182</sup>W<sup>32</sup>S, <sup>183</sup>W<sup>32</sup>S, <sup>184</sup>W<sup>32</sup>S, and <sup>186</sup>W<sup>32</sup>S, were measured and a rotational analysis was performed using PGOPHER. A constrained parameters approach was used to maintain expected mass relationships among isotopologues. This analysis increases the number of observed rotational levels from J ∼ 30 to J ∼ 100 for both excited states, allowing an increase in precision of spectroscopic constants. The new analysis of the [15.30]1 <strong>–</strong> <em>X</em> <sup>3</sup>Σ<sup>−</sup>(1) transition enabled the reduced uncertainty in the previously determined value for the splitting of the 0+ and 1 Ω-components of the <em>X</em> <sup>3</sup>Σ<sup>−</sup> ground state. Also presented in this work is an expansion upon our earlier deperturbation analysis involving the [15.30]1 state to include the v′ = 2 vibrational level, which is perturbed by the v′ = 4 vibrational level of the [14.26]0<sup>+</sup> state.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"408 ","pages":"Article 111999"},"PeriodicalIF":1.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143201823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.jms.2025.111997
Lukas Meinschad , Kemal Oenen , Dennis F. Dinu , Klaus R. Liedl
The hydrogen bond (HB), a non-covalent interaction, leads to diverse structural motifs that dictate the physical properties of materials or biochemical processes. Infrared spectroscopy allows straightforward access to such structural motifs from laboratory experiments. These spectra indirectly reveal HBs through vibrational frequency shifts in a molecular cluster compared to the single molecules. Characterizing these shifts with descriptive vibrational notations is challenging due to the delocalized nature of intermolecular vibrations. Typically, vibrations of clusters are represented in terms of the respective individual molecules. This approach is somewhat debatable, mainly when notations are based on experience or visual interpretation of theoretical models, most notably the normal mode framework. While normal modes are straightforward to obtain, they often provide insufficient descriptions of delocalized vibrations. Here, the decomposition of normal modes into contributions from internal coordinates allows for both an illustrative framework and a quantitative basis for vibrational notations. In the present work, we apply such a decomposition scheme to various HB systems, assessing the plausibility of notations used in IR spectroscopy of molecular clusters. For water, methanol, and clusters thereof, we demonstrate the limitations of conventional notations and how normal mode decomposition schemes can provide a reasonable workaround.
{"title":"Toward less ambiguous vibrational spectroscopic notations for hydrogen-bonded water and methanol clusters","authors":"Lukas Meinschad , Kemal Oenen , Dennis F. Dinu , Klaus R. Liedl","doi":"10.1016/j.jms.2025.111997","DOIUrl":"10.1016/j.jms.2025.111997","url":null,"abstract":"<div><div>The hydrogen bond (HB), a non-covalent interaction, leads to diverse structural motifs that dictate the physical properties of materials or biochemical processes. Infrared spectroscopy allows straightforward access to such structural motifs from laboratory experiments. These spectra indirectly reveal HBs through vibrational frequency shifts in a molecular cluster compared to the single molecules. Characterizing these shifts with descriptive vibrational notations is challenging due to the delocalized nature of intermolecular vibrations. Typically, vibrations of clusters are represented in terms of the respective individual molecules. This approach is somewhat debatable, mainly when notations are based on experience or visual interpretation of theoretical models, most notably the normal mode framework. While normal modes are straightforward to obtain, they often provide insufficient descriptions of delocalized vibrations. Here, the decomposition of normal modes into contributions from <em>internal coordinates</em> allows for both an illustrative framework and a quantitative basis for vibrational notations. In the present work, we apply such a decomposition scheme to various HB systems, assessing the plausibility of notations used in IR spectroscopy of molecular clusters. For water, methanol, and clusters thereof, we demonstrate the limitations of conventional notations and how normal mode decomposition schemes can provide a reasonable workaround.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"408 ","pages":"Article 111997"},"PeriodicalIF":1.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143133826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.jms.2024.111967
Luis Bonah , Benedikt Helmstaedter , Jean-Claude Guillemin , Stephan Schlemmer , Sven Thorwirth
Cyclopentadiene ( ) is a cyclic pure hydrocarbon that was already detected astronomically towards the prototypical dark cloud TMC-1 (Cernicharo et al., 2021). However, accurate predictions of its rotational spectrum are still limited to the microwave region and narrow quantum number ranges. In the present study, the pure rotational spectrum of cyclopentadiene was measured in the frequency ranges 170–250 GHz and 340–510 GHz to improve the number of vibrational ground state assignments by more than a factor of 20, resulting in more accurate rotational parameters and the determination of higher-order centrifugal distortion parameters. Additionally, vibrational satellite spectra of cyclopentadiene in its eight energetically lowest vibrationally excited states were analyzed for the first time. Coriolis interactions between selected vibrational states were identified and treated successfully in combined fits. Previous microwave work on the three singly substituted isotopologues was extended significantly also covering frequency ranges up to 250 GHz. The new data sets permit reliable frequency predictions for the isotopologues and vibrational satellite spectra far into the sub-mm-wave range. Finally, the experimental rotational constants of all available isotopologues and calculated zero-point vibrational contributions to the rotational constants were used to derive a semi-experimental equilibrium structure of this fundamental ring molecule.
{"title":"Extending the rotational spectrum of cyclopentadiene towards higher frequencies and vibrational states","authors":"Luis Bonah , Benedikt Helmstaedter , Jean-Claude Guillemin , Stephan Schlemmer , Sven Thorwirth","doi":"10.1016/j.jms.2024.111967","DOIUrl":"10.1016/j.jms.2024.111967","url":null,"abstract":"<div><div>Cyclopentadiene ( <figure><img></figure> ) is a cyclic pure hydrocarbon that was already detected astronomically towards the prototypical dark cloud TMC-1 (Cernicharo et al., 2021). However, accurate predictions of its rotational spectrum are still limited to the microwave region and narrow quantum number ranges. In the present study, the pure rotational spectrum of cyclopentadiene was measured in the frequency ranges 170–250<!--> <!-->GHz and 340–510<!--> <!-->GHz to improve the number of vibrational ground state assignments by more than a factor of 20, resulting in more accurate rotational parameters and the determination of higher-order centrifugal distortion parameters. Additionally, vibrational satellite spectra of cyclopentadiene in its eight energetically lowest vibrationally excited states were analyzed for the first time. Coriolis interactions between selected vibrational states were identified and treated successfully in combined fits. Previous microwave work on the three singly <figure><img></figure> substituted isotopologues was extended significantly also covering frequency ranges up to 250<!--> <!-->GHz. The new data sets permit reliable frequency predictions for the isotopologues and vibrational satellite spectra far into the sub-mm-wave range. Finally, the experimental rotational constants of all available isotopologues and calculated zero-point vibrational contributions to the rotational constants were used to derive a semi-experimental equilibrium structure of this fundamental ring molecule.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"408 ","pages":"Article 111967"},"PeriodicalIF":1.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143133827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.jms.2025.111985
Isiah M. McMurray, Joseph R. Nettles, Aaron W. Uzelmeier, Jeremy A. Swartz, Josh J. Newby
The weakly bound complexes of N-methyl-2-pyrrolidone (NMP) and water have been analyzed using a combination of computational methods and matrix isolation FTIR spectroscopy. The computational analysis utilized density functional and perturbation theory methods to determine the lowest energy geometries and vibrational frequencies of NMP: H2O. This analysis yielded four unique structures that could be differentiated by their preferred intermolecular interaction. Two structures formed via relatively strong OH⋯O hydrogen bonds, one structure was stabilized via OH⋯N interactions, and the fourth structure was observed to interact through relatively weak CH⋯O features. The interaction motifs were verified using atoms in molecules analysis and the noncovalent interaction index method. Spectra of NMP with H2O and its isotopologues showed clear evidence of two unique structures in the cryogenic nitrogen matrix. Both of these structures formed through OH⋯O interactions from the water to the carbonyl oxygen of NMP. This structural assignment was supported by the calculated vibrational shifts seen in NMP: H2O. A detailed analysis and discussion of this assignment is provided.
{"title":"An analysis of the N-methyl-2-pyrrolidone: water complex using computational and matrix isolation FTIR methods","authors":"Isiah M. McMurray, Joseph R. Nettles, Aaron W. Uzelmeier, Jeremy A. Swartz, Josh J. Newby","doi":"10.1016/j.jms.2025.111985","DOIUrl":"10.1016/j.jms.2025.111985","url":null,"abstract":"<div><div>The weakly bound complexes of <em>N</em>-methyl-2-pyrrolidone (NMP) and water have been analyzed using a combination of computational methods and matrix isolation FTIR spectroscopy. The computational analysis utilized density functional and perturbation theory methods to determine the lowest energy geometries and vibrational frequencies of NMP: H<sub>2</sub>O. This analysis yielded four unique structures that could be differentiated by their preferred intermolecular interaction. Two structures formed via relatively strong OH⋯O hydrogen bonds, one structure was stabilized via OH⋯N interactions, and the fourth structure was observed to interact through relatively weak CH⋯O features. The interaction motifs were verified using atoms in molecules analysis and the noncovalent interaction index method. Spectra of NMP with H<sub>2</sub>O and its isotopologues showed clear evidence of two unique structures in the cryogenic nitrogen matrix. Both of these structures formed through OH⋯O interactions from the water to the carbonyl oxygen of NMP. This structural assignment was supported by the calculated vibrational shifts seen in NMP: H<sub>2</sub>O. A detailed analysis and discussion of this assignment is provided.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"408 ","pages":"Article 111985"},"PeriodicalIF":1.4,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143133828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jms.2024.111979
Haiying Huang, Xiaolong Li, Gang Feng
We investigated the non-covalent interactions occurring between benzofuran and water. The weakly-bound complex was produced using a supersonic jet expansion and was subsequently characterized utilizing high-resolution Fourier transform microwave spectroscopy. Through the analysis of the rotational spectrum, we were able to confirm the detection of two distinct conformations within the complex. The most stable conformation demonstrates a structure that is almost coplanar. This structure involves one hydrogen atom from a water molecule interacting with the oxygen atom of benzofuran, thus forming an Ow–Hw···O hydrogen bond. Concurrently, the oxygen atom serves as a proton acceptor, forming an Ow···HC hydrogen bond with one hydrogen atom of the phenyl ring. The secondary conformation positions the two OH bonds such that they are oriented towards the face of benzofuran, resulting in the formation of two Ow–Hw···π hydrogen bonds. The non-covalent bonding topology of the first conformation bears resemblance to the corresponding furan-water complex, while the second conformation aligns with the benzofuran-hydrogen sulfide complex. The strength and the nature of these hydrogen bonding interactions is delineated by the application of natural bond orbital theory, energy decomposition, and electronic density analysis methodologies.
{"title":"Rotational spectroscopy of the benzofuran–water complex: Conformations and preferred noncovalent interactions","authors":"Haiying Huang, Xiaolong Li, Gang Feng","doi":"10.1016/j.jms.2024.111979","DOIUrl":"10.1016/j.jms.2024.111979","url":null,"abstract":"<div><div>We investigated the non-covalent interactions occurring between benzofuran and water. The weakly-bound complex was produced using a supersonic jet expansion and was subsequently characterized utilizing high-resolution Fourier transform microwave spectroscopy. Through the analysis of the rotational spectrum, we were able to confirm the detection of two distinct conformations within the complex. The most stable conformation demonstrates a structure that is almost coplanar. This structure involves one hydrogen atom from a water molecule interacting with the oxygen atom of benzofuran, thus forming an O<sub>w</sub>–H<sub>w</sub>···O hydrogen bond. Concurrently, the oxygen atom serves as a proton acceptor, forming an O<sub>w</sub>···H<img>C hydrogen bond with one hydrogen atom of the phenyl ring. The secondary conformation positions the two O<img>H bonds such that they are oriented towards the face of benzofuran, resulting in the formation of two O<sub>w</sub>–H<sub>w</sub>···π hydrogen bonds. The non-covalent bonding topology of the first conformation bears resemblance to the corresponding furan-water complex, while the second conformation aligns with the benzofuran-hydrogen sulfide complex. The strength and the nature of these hydrogen bonding interactions is delineated by the application of natural bond orbital theory, energy decomposition, and electronic density analysis methodologies.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"407 ","pages":"Article 111979"},"PeriodicalIF":1.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143170360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jms.2024.111984
Shuo Zhao , Jie Gao , Yongqi Wu , Rui Zhu , Mu Li , Wanyi Qin , Xijun Wu , Yungang Zhang
Oxygen (O2) and ozone (O3) are of crucial importance to human health and environmental sustainability. Concentrations of O2 and O3 can be measured by UV absorption spectroscopy, in which the absorption cross-section (ACS) is a very critical physical parameter for calculating concentrations. However, the existing ACS of O2 and O3 are biased because the conversion of O2 to O3 and nonlinear effects in absorption are ignored in the measurement of ACS. In this study, the ACS for O2 and O3 are obtained by considering the conversion of O2 to O3 and the nonlinear effects. First, the conversion of O2 to O3 is inhibited by controlling gas flow rate and light intensity in the measurement of O2 and O3 ACS. Then the concentration of O3 is indirectly calculated by controlling conversion of O2 to O3 during the measurement of ACS of O3. Next, the linear-absorption regions for O2 and O3 are determined by constructing the relationship between absorption intensities and concentrations to eliminate the influence of nonlinear effect. The maximum ACS for oxygen and ozone are cm2/molecule ( = 180.51 nm) and cm2/molecule ( = 255.39 nm) by controlling conversion of O2 to O3 in the linear-absorption region, respectively.
{"title":"Measurement of O2 and O3 absorption cross-sections in the 180–270 nm by controlling the conversion of O2 to O3 in the linear-absorption region","authors":"Shuo Zhao , Jie Gao , Yongqi Wu , Rui Zhu , Mu Li , Wanyi Qin , Xijun Wu , Yungang Zhang","doi":"10.1016/j.jms.2024.111984","DOIUrl":"10.1016/j.jms.2024.111984","url":null,"abstract":"<div><div>Oxygen (O<sub>2</sub>) and ozone (O<sub>3</sub>) are of crucial importance to human health and environmental sustainability. Concentrations of O<sub>2</sub> and O<sub>3</sub> can be measured by UV absorption spectroscopy, in which the absorption cross-section (ACS) is a very critical physical parameter for calculating concentrations. However, the existing ACS of O<sub>2</sub> and O<sub>3</sub> are biased because the conversion of O<sub>2</sub> to O<sub>3</sub> and nonlinear effects in absorption are ignored in the measurement of ACS. In this study, the ACS for O<sub>2</sub> and O<sub>3</sub> are obtained by considering the conversion of O<sub>2</sub> to O<sub>3</sub> and the nonlinear effects. First, the conversion of O<sub>2</sub> to O<sub>3</sub> is inhibited by controlling gas flow rate and light intensity in the measurement of O<sub>2</sub> and O<sub>3</sub> ACS. Then the concentration of O<sub>3</sub> is indirectly calculated by controlling conversion of O<sub>2</sub> to O<sub>3</sub> during the measurement of ACS of O<sub>3</sub>. Next, the linear-absorption regions for O<sub>2</sub> and O<sub>3</sub> are determined by constructing the relationship between absorption intensities and concentrations to eliminate the influence of nonlinear effect. The maximum ACS for oxygen and ozone are <span><math><mrow><mn>7.84</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>-</mo><mn>20</mn></mrow></msup></mrow></math></span> cm<sup>2</sup>/molecule (<span><math><mrow><mi>λ</mi></mrow></math></span> = 180.51 nm) and <span><math><mrow><mn>1.32</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>-</mo><mn>17</mn></mrow></msup></mrow></math></span> cm<sup>2</sup>/molecule (<span><math><mrow><mi>λ</mi></mrow></math></span> = 255.39 nm) by controlling conversion of O<sub>2</sub> to O<sub>3</sub> in the linear-absorption region, respectively.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"407 ","pages":"Article 111984"},"PeriodicalIF":1.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jms.2024.111978
Carlo Baddeliyanage , Joshua Karner , Sruthi Purushu Melath , Weslley G.D.P. Silva , Stephan Schlemmer , Oskar Asvany
The rotational spectrum of linear CH has been revisited in the millimeter-wave region using a cryogenic ion trap apparatus employing a double-resonance scheme based on leak-out action spectroscopy (LOS). Eight rotational transitions ( up to ) have been measured in the 85-250GHz frequency range. With the laboratory measurements reported here, improved values for the ground-state spectroscopic constants of CH have been obtained.
{"title":"Extending the laboratory rotational spectrum of linear C3H+","authors":"Carlo Baddeliyanage , Joshua Karner , Sruthi Purushu Melath , Weslley G.D.P. Silva , Stephan Schlemmer , Oskar Asvany","doi":"10.1016/j.jms.2024.111978","DOIUrl":"10.1016/j.jms.2024.111978","url":null,"abstract":"<div><div>The rotational spectrum of linear C<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>H<span><math><msup><mrow></mrow><mrow><mo>+</mo></mrow></msup></math></span> has been revisited in the millimeter-wave region using a cryogenic ion trap apparatus employing a double-resonance scheme based on leak-out action spectroscopy (LOS). Eight rotational transitions (<span><math><mrow><msup><mrow><mi>J</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>←</mo><msup><mrow><mi>J</mi></mrow><mrow><mo>′</mo><mo>′</mo></mrow></msup><mo>=</mo><mn>4</mn><mo>←</mo><mn>3</mn></mrow></math></span> up to <span><math><mrow><msup><mrow><mi>J</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>←</mo><msup><mrow><mi>J</mi></mrow><mrow><mo>′</mo><mo>′</mo></mrow></msup><mo>=</mo><mn>11</mn><mo>←</mo><mn>10</mn></mrow></math></span>) have been measured in the 85-250<span><math><mspace></mspace></math></span>GHz frequency range. With the laboratory measurements reported here, improved values for the ground-state spectroscopic constants of C<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>H<span><math><msup><mrow></mrow><mrow><mo>+</mo></mrow></msup></math></span> have been obtained.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"407 ","pages":"Article 111978"},"PeriodicalIF":1.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jms.2024.111968
Surabhi Gupta , Charlotte N. Cummings , Nicholas R. Walker , Elangannan Arunan
Rotational spectra of 1-fluoronaphthalene isotopologues have been recorded using a chirped-pulse Fourier transform microwave spectrometer in the 2.0–8.0 GHz frequency range using neon as a carrier gas. Ten 13C isotopomers (each containing only a single 12C/13C substitution) of 1-fluoronaphthalene have been assigned in natural abundance for the first time. The rotational constants A0, B0, and C0 and inertial defects are determined from experimentally measured transition frequencies. For all isotopologues, the measured values of inertial defects were observed to fall within the range from −0.142 to −0.145 u Å2. The negative inertial defects are attributed to the low frequency, out-of-plane bending mode of the 1-fluoronaphthalene ring, which is evidently of similar frequency in each isotopologue. The anharmonic frequency of this mode has been calculated to be 142.8 cm−1 at the B3LYP-D3/cc-pVTZ level of theory, compared to 94 cm−1 predicted from the inertial defect based on an empirical relation proposed by Oka. Recent, unpublished, THz Raman spectrum reveals a peak at 75 cm−1, which is closer to the empirical prediction.
{"title":"Revisiting the microwave spectrum and molecular structure of 1-fluoronaphthalene","authors":"Surabhi Gupta , Charlotte N. Cummings , Nicholas R. Walker , Elangannan Arunan","doi":"10.1016/j.jms.2024.111968","DOIUrl":"10.1016/j.jms.2024.111968","url":null,"abstract":"<div><div>Rotational spectra of 1-fluoronaphthalene isotopologues have been recorded using a chirped-pulse Fourier transform microwave spectrometer in the 2.0–8.0 GHz frequency range using neon as a carrier gas. Ten <sup>13</sup>C isotopomers (each containing only a single <sup>12</sup>C/<sup>13</sup>C substitution) of 1-fluoronaphthalene have been assigned in natural abundance for the first time. The rotational constants <em>A</em><sub>0</sub>, <em>B</em><sub>0</sub>, and <em>C</em><sub>0</sub> and inertial defects are determined from experimentally measured transition frequencies. For all isotopologues, the measured values of inertial defects were observed to fall within the range from −0.142 to −0.145 u Å<sup>2</sup>. The negative inertial defects are attributed to the low frequency, out-of-plane bending mode of the 1-fluoronaphthalene ring, which is evidently of similar frequency in each isotopologue. The anharmonic frequency of this mode has been calculated to be 142.8 cm<sup>−1</sup> at the B3LYP-D3/cc-pVTZ level of theory, compared to 94 cm<sup>−1</sup> predicted from the inertial defect based on an empirical relation proposed by Oka. Recent, unpublished, THz Raman spectrum reveals a peak at 75 cm<sup>−1</sup>, which is closer to the empirical prediction.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"407 ","pages":"Article 111968"},"PeriodicalIF":1.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.jms.2024.111977
V.G. Ushakov , A. Yu. Ermilov , E.S. Medvedev
<div><div>The best available line list of OH [Brooke et al. JQSRT, 168 (2016) 142] contains the high-quality line frequencies, yet the line intensities need refinement because the model function used to interpolate the RKR potential and to extrapolate it into the repulsion region was not analytic [Medvedev et al. Mol. Phys. doi: 10.1080/00268976.2024.2395439], and also because the coupling between the ground <span><math><mrow><msup><mrow><mi>X</mi></mrow><mrow><mn>2</mn></mrow></msup><mi>Π</mi></mrow></math></span> and first excited <span><math><mrow><msup><mrow><mi>A</mi></mrow><mrow><mn>2</mn></mrow></msup><msup><mrow><mi>Σ</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow></math></span> electronic states was treated by the perturbation theory. In this paper, we performed <em>ab initio</em> calculations of all necessary molecular functions at <span><math><mrow><mi>r</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>4</mn></mrow></math></span>-8.0 bohr, and then we construct fully analytic model functions entering the Hamiltonian. The model functions were fitted to both the <em>ab initio</em> data and the available experimental data on the line positions and energy levels, the relative line intensities, and the transition dipole moments derived from the measured permanent dipoles. The system of three coupled Schrödinger equations for two multiplet components of the <span><math><mi>X</mi></math></span> state plus the <span><math><mi>A</mi></math></span> state was solved to calculate the energy levels and the line intensities. The new set of the Einstein <em>A</em> coefficients permits to decrease the scatter of the logarithmic populations of the ro-vibrational levels derived from the observed radiation fluxes [Noll et al. Atmos. Chem. Phys. 20 (2020) 5269], to achieve better agreement with the measured relative intensities, and to obtain significant differences in the intensities of the <span><math><mi>Λ</mi></math></span> doublets for large <span><math><mi>v</mi></math></span> and <span><math><mi>J</mi></math></span> as observed by Noll et al. The <span><math><mi>X</mi></math></span>-<span><math><mi>A</mi></math></span> coupling fully modifies the Q-line intensities at high <span><math><mi>J</mi></math></span> by removing the well-known <span><math><msup><mrow><mi>J</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></math></span> dependence. A new line list is constructed where the transition frequencies are from Brooke et al. and the Einstein <span><math><mi>A</mi></math></span> coefficients are from the present study. However, not all the problems with the intensities were resolved, presumably due to the neglect of the interaction with the <span><math><mrow><msup><mrow></mrow><mrow><mn>4</mn></mrow></msup><msup><mrow><mi>Σ</mi></mrow><mrow><mo>−</mo></mrow></msup><msup><mrow><mo>,</mo></mrow><mrow><mn>2</mn></mrow></msup><msup><mrow><mi>Σ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math></span> and <span><math><mrow><msup><mrow></mrow><mrow><mn>4</mn
{"title":"Three-states model for calculating the X-X rovibrational transition intensities in hydroxyl radical","authors":"V.G. Ushakov , A. Yu. Ermilov , E.S. Medvedev","doi":"10.1016/j.jms.2024.111977","DOIUrl":"10.1016/j.jms.2024.111977","url":null,"abstract":"<div><div>The best available line list of OH [Brooke et al. JQSRT, 168 (2016) 142] contains the high-quality line frequencies, yet the line intensities need refinement because the model function used to interpolate the RKR potential and to extrapolate it into the repulsion region was not analytic [Medvedev et al. Mol. Phys. doi: 10.1080/00268976.2024.2395439], and also because the coupling between the ground <span><math><mrow><msup><mrow><mi>X</mi></mrow><mrow><mn>2</mn></mrow></msup><mi>Π</mi></mrow></math></span> and first excited <span><math><mrow><msup><mrow><mi>A</mi></mrow><mrow><mn>2</mn></mrow></msup><msup><mrow><mi>Σ</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow></math></span> electronic states was treated by the perturbation theory. In this paper, we performed <em>ab initio</em> calculations of all necessary molecular functions at <span><math><mrow><mi>r</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>4</mn></mrow></math></span>-8.0 bohr, and then we construct fully analytic model functions entering the Hamiltonian. The model functions were fitted to both the <em>ab initio</em> data and the available experimental data on the line positions and energy levels, the relative line intensities, and the transition dipole moments derived from the measured permanent dipoles. The system of three coupled Schrödinger equations for two multiplet components of the <span><math><mi>X</mi></math></span> state plus the <span><math><mi>A</mi></math></span> state was solved to calculate the energy levels and the line intensities. The new set of the Einstein <em>A</em> coefficients permits to decrease the scatter of the logarithmic populations of the ro-vibrational levels derived from the observed radiation fluxes [Noll et al. Atmos. Chem. Phys. 20 (2020) 5269], to achieve better agreement with the measured relative intensities, and to obtain significant differences in the intensities of the <span><math><mi>Λ</mi></math></span> doublets for large <span><math><mi>v</mi></math></span> and <span><math><mi>J</mi></math></span> as observed by Noll et al. The <span><math><mi>X</mi></math></span>-<span><math><mi>A</mi></math></span> coupling fully modifies the Q-line intensities at high <span><math><mi>J</mi></math></span> by removing the well-known <span><math><msup><mrow><mi>J</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></math></span> dependence. A new line list is constructed where the transition frequencies are from Brooke et al. and the Einstein <span><math><mi>A</mi></math></span> coefficients are from the present study. However, not all the problems with the intensities were resolved, presumably due to the neglect of the interaction with the <span><math><mrow><msup><mrow></mrow><mrow><mn>4</mn></mrow></msup><msup><mrow><mi>Σ</mi></mrow><mrow><mo>−</mo></mrow></msup><msup><mrow><mo>,</mo></mrow><mrow><mn>2</mn></mrow></msup><msup><mrow><mi>Σ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math></span> and <span><math><mrow><msup><mrow></mrow><mrow><mn>4</mn","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"407 ","pages":"Article 111977"},"PeriodicalIF":1.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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