Pub Date : 2025-02-01Epub Date: 2024-12-18DOI: 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.
环戊二烯（Cyclopentadiene）是一种环纯碳氢化合物，在天文学上已经探测到它靠近典型的黑云TMC-1 （Cernicharo et al., 2021）。然而，对其旋转谱的准确预测仍然局限于微波区和较窄的量子数范围。在本研究中，环戊二烯的纯旋转光谱在170-250 GHz和340-510 GHz频率范围内进行了测量，将振动基态分配的数量提高了20倍以上，从而获得了更精确的旋转参数和高阶离心畸变参数的确定。此外，首次分析了环戊二烯在其8个能量最低振动激发态下的振动卫星谱。选定的振动状态之间的科里奥利相互作用被识别并成功地在组合拟合中处理。以前对三种单取代同位素的微波工作已大大扩展，频率范围也达到250千兆赫。新的数据集允许对远至亚毫米波范围的同位素和振动卫星谱进行可靠的频率预测。最后，利用所有可用同位素的实验旋转常数和计算的零点振动对旋转常数的贡献，推导出该基本环分子的半实验平衡结构。
{"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 : 2025-02-01Epub Date: 2025-01-09DOI: 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 : 2025-01-01Epub Date: 2024-12-11DOI: 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 : 2025-01-01Epub Date: 2024-12-29DOI: 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 : 2025-01-01Epub Date: 2024-11-29DOI: 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}
The rotational spectrum of 2’-aminoacetophenone has been recorded and assigned using a Stark-modulated Free-Jet Absorption Millimeter-Wave (FJ-AMMW) spectrometer in the 59.6–74.4 GHz frequency range. Some transition lines show a hyperfine structure due to the internal rotation of the methyl group. A global fitting including previous measurements performed in the microwave region allowed the determination of the and quartic centrifugal distortion constants and methyl internal rotation barrier = 644(3) cm−1 value. The A–E tunnelling splitting is estimated to be = 23 MHz. Calculations at the MP2/aug-cc-pVTZ level underestimate the height of the barrier by about 23 cm−1. This difference increases to 150 cm−1 with B3LYP-D3(BJ)/Def2-TZVP.
{"title":"Free-jet absorption millimeter-wave spectrum of 2’-aminoacetophenone","authors":"Salvatore Boi , Sonia Melandri , Luca Evangelisti , Assimo Maris","doi":"10.1016/j.jms.2024.111966","DOIUrl":"10.1016/j.jms.2024.111966","url":null,"abstract":"<div><div>The rotational spectrum of 2’-aminoacetophenone has been recorded and assigned using a Stark-modulated Free-Jet Absorption Millimeter-Wave (FJ-AMMW) spectrometer in the 59.6–74.4 GHz frequency range. Some transition lines show a hyperfine structure due to the internal rotation of the methyl group. A global fitting including previous measurements performed in the microwave region allowed the determination of the <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>J</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>K</mi></mrow></msub></math></span> quartic centrifugal distortion constants and methyl internal rotation barrier <span><math><msub><mrow><mi>V</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> = 644(3) cm<sup>−1</sup> value. The A–E tunnelling splitting is estimated to be <span><math><msub><mrow><mi>Δ</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> = 23 MHz. Calculations at the MP2/aug-cc-pVTZ level underestimate the height of the <span><math><msub><mrow><mi>V</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> barrier by about 23 cm<sup>−1</sup>. This difference increases to 150 cm<sup>−1</sup> with B3LYP-D3(BJ)/Def2-TZVP.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"407 ","pages":"Article 111966"},"PeriodicalIF":1.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171334","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 : 2025-01-01Epub Date: 2024-12-16DOI: 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}
Pub Date : 2025-01-01Epub Date: 2024-11-26DOI: 10.1016/j.jms.2024.111965
Leonid N. Sinitsa , Nikolai F. Zobov , Mikhail A. Rogov , Jonathan Tennyson , Oleg L. Polyansky
A spectrum of HD17O in the region between 5 480 and 6 400 recorded in Tomsk is reported. In this region 4292 lines are observed belonging to 7 water isotopologues: 536 lines – HO 1019 – HD16O, 122 – D O, 447 – HO 458 – HD17O, 151 – HO, 181 – HD18O. A new potential energy surface (PES) of HD16O is obtained by fitting to empirical energy levels. This PES, with a diagonal Born–Oppenheimer correction (DBOC), is used to compute the HD17O spectrum. Pseudo-experimental isotopologue-extrapolation energy levels of HD17O are constructed using the method of Polyansky et al (MNRAS 466, 1363 (2017)). Assignment of the measured spectrum is conducted: 68 % of the lines can be assigned using assignments from previously published work. The remaining lines are assigned using the pseudo-experimental energy levels procedure. We compare the calculated pseudo-experimental values of energy levels with both existing 1285 experimental levels of HD17O and the 152 newly determined in this work energy levels. The standard deviation of levels with low J (up to J=10) is about 0.007 in both cases. Energy levels from both pseudo-experimental and variationally calculated are also compared with newly measured HD17O lines above 10 000 .
{"title":"Study of HD17O spectrum. Theory and experiment","authors":"Leonid N. Sinitsa , Nikolai F. Zobov , Mikhail A. Rogov , Jonathan Tennyson , Oleg L. Polyansky","doi":"10.1016/j.jms.2024.111965","DOIUrl":"10.1016/j.jms.2024.111965","url":null,"abstract":"<div><div>A spectrum of HD<sup>17</sup>O in the region between 5 480 and 6 400 <span><math><msup><mrow><mtext>cm</mtext></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> recorded in Tomsk is reported. In this region 4292 lines are observed belonging to 7 water isotopologues: 536 lines – H<span><math><mrow><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub><msup><mrow></mrow><mrow><mn>16</mn></mrow></msup></mrow></math></span>O<!--> <!-->1019 – HD<sup>16</sup>O, 122 – D<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> <span><math><msup><mrow></mrow><mrow><mn>16</mn></mrow></msup></math></span>O, 447 – H<span><math><mrow><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub><msup><mrow></mrow><mrow><mn>17</mn></mrow></msup></mrow></math></span>O<!--> <!-->458 – HD<sup>17</sup>O, 151 – H<span><math><msubsup><mrow></mrow><mrow><mn>2</mn></mrow><mrow><mn>18</mn></mrow></msubsup></math></span>O, 181 – HD<sup>18</sup>O. A new potential energy surface (PES) of HD<sup>16</sup>O is obtained by fitting to empirical energy levels. This PES, with a diagonal Born–Oppenheimer correction (DBOC), is used to compute the HD<sup>17</sup>O spectrum. Pseudo-experimental isotopologue-extrapolation energy levels of HD<sup>17</sup>O are constructed using the method of Polyansky et al (MNRAS 466, 1363 (2017)). Assignment of the measured spectrum is conducted: 68 % of the lines can be assigned using assignments from previously published work. The remaining lines are assigned using the pseudo-experimental energy levels procedure. We compare the calculated pseudo-experimental values of energy levels with both existing 1285 experimental levels of HD<sup>17</sup>O and the 152 newly determined in this work energy levels. The standard deviation of levels with low J (up to J=10) is about 0.007 <span><math><msup><mrow><mtext>cm</mtext></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> in both cases. Energy levels from both pseudo-experimental and variationally calculated are also compared with newly measured HD<sup>17</sup>O lines above 10 000 <span><math><msup><mrow><mtext>cm</mtext></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"407 ","pages":"Article 111965"},"PeriodicalIF":1.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171341","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 : 2025-01-01Epub Date: 2024-12-20DOI: 10.1016/j.jms.2024.111981
Khaled El-Shazly, Heather R. Legg, Jayden Wilkinson, David Kapp, Laura R. McCunn
One commonly observed product of the pyrolysis of many types of biomass is the cyclic oxygenated heterocycle 2-pyrone (2H-Pyran-2-one). Applying matrix-isolation techniques, the thermal decomposition products of 2-pyrone were identified by depositing a diluted mixture of sample and argon through a heated SiC tube onto a cold CsI window, which was then characterized by FT-IR. Experimental spectra collected following pyrolysis at 1400 K indicate the formation of acetylene, vinylacetylene, propargyl, propyne, allyl, carbon dioxide, carbon monoxide, ketene, and furan. Several bands in the vicinity of the antisymmetric CCO stretch of ketene are tentatively assigned to vinylketene and formylvinylketene. Computational analysis using Gaussian 09 at the B3LYP/6-311++G (d,p) level of theory was performed to further confirm product assignments. The results of this study are consistent with published theoretical and computational studies of the pyrolysis of furfural, of which 2-pyrone is a reaction intermediate.
{"title":"Characterization of the pyrolysis products of 2-pyrone via matrix-isolation FTIR","authors":"Khaled El-Shazly, Heather R. Legg, Jayden Wilkinson, David Kapp, Laura R. McCunn","doi":"10.1016/j.jms.2024.111981","DOIUrl":"10.1016/j.jms.2024.111981","url":null,"abstract":"<div><div>One commonly observed product of the pyrolysis of many types of biomass is the cyclic oxygenated heterocycle 2-pyrone (2H-Pyran-2-one). Applying matrix-isolation techniques, the thermal decomposition products of 2-pyrone were identified by depositing a diluted mixture of sample and argon through a heated SiC tube onto a cold CsI window, which was then characterized by FT-IR. Experimental spectra collected following pyrolysis at 1400 K indicate the formation of acetylene, vinylacetylene, propargyl, propyne, allyl, carbon dioxide, carbon monoxide, ketene, and furan. Several bands in the vicinity of the antisymmetric C<img>C<img>O stretch of ketene are tentatively assigned to vinylketene and formylvinylketene. Computational analysis using Gaussian 09 at the B3LYP/6-311++G (d,p) level of theory was performed to further confirm product assignments. The results of this study are consistent with published theoretical and computational studies of the pyrolysis of furfural, of which 2-pyrone is a reaction intermediate.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"407 ","pages":"Article 111981"},"PeriodicalIF":1.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171322","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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