Journal of Molecular Spectroscopy最新文献

{"title":"The tunneling splittings of the ground state and some excited vibrational states for the inversion motion in H3C− anion and H3Si radical","authors":"George A. Pitsevich ,&nbsp;Alex E. Malevich ,&nbsp;Maksim Shundalau","doi":"10.1016/j.jms.2024.111906","DOIUrl":"10.1016/j.jms.2024.111906","url":null,"abstract":"<div><p>Splitting of the ground state and some excited symmetric bending vibrational states due to inversion tunneling in the H₃C⁻ anion and H₃Si^<img> radical is analyzed by numerically solving the vibrational Schrödinger equation of restricted (2D) dimensionality. We used the following two vibrational coordinates for the H₃X structure (X = C, Si): the distance of the X atom from the plane of a regular triangle formed by three hydrogen atoms (1) and a symmetry coordinate composed of three distances between chemically non-bonded hydrogen atoms (2). The kinetic energy operator in this case takes the simplest form. The 2D potential energy surface (PES) in the given coordinates was calculated for H₃C⁻ at the CCSD(T)/aug-cc-pVTZ, CCSD(T)/aug-cc-pVQZ, CCSD(T)/aug-cc-pV5Z, CCSD(T)/CBS(TQ5), CCSD(T)/d-aug-cc-pVTZ, CCSD(T)/<em>t</em>-aug-cc-pVTZ, and CCSD(T)/q-aug-cc-pVTZ levels of theory, based on recommendations from recently published work [M.C. Bowman, B. Zhang, W.J. Morgan, H.F. Schaefer III, Mol.Phys., 117 (2019) 1069–1077]. The same 2D PES for the H₃Si^<img> radical was calculated at the CCSD(T)/aug-cc-pVDZ CCSD(T)/aug-cc-pVTZ, CCSD(T)/aug-cc-pVQZ, and CCSD(T)/CBS(D,T,Q) as well as at the CCSD(T)/d-aug-cc-pVTZ, CCSD(T)/un-aug-cc-pVTZ, CCSD(T)/un-aug-cc-pVQZ levels of theory. The tunneling splittings for the D₃C⁻ anion and D₃Si^<img> radical were calculated as well. The results of calculations demonstrate good agreement with available experimental data on umbrella vibration frequencies and inversion splittings for the title molecules.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140775401","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}

{"title":"The C1Πu state of potassium dimer revisited: An extensive study by polarisation labelling spectroscopy method","authors":"Wlodzimierz Jastrzebski ,&nbsp;Jacek Szczepkowski ,&nbsp;Pawel Kowalczyk","doi":"10.1016/j.jms.2024.111905","DOIUrl":"https://doi.org/10.1016/j.jms.2024.111905","url":null,"abstract":"<div><p>The polarisation labelling spectroscopy technique was applied to study the C<span><math><mrow><msup><mrow></mrow><mrow><mn>1</mn></mrow></msup><msub><mrow><mi>Π</mi></mrow><mrow><mi>u</mi></mrow></msub></mrow></math></span> <span><math><mo>←</mo></math></span> X<span><math><mrow><msup><mrow></mrow><mrow><mn>1</mn></mrow></msup><msubsup><mrow><mi>Σ</mi></mrow><mrow><mi>g</mi></mrow><mrow><mo>+</mo></mrow></msubsup></mrow></math></span> band system in potassium dimer. About 1100 new rotationally resolved molecular lines were measured in the 22100–24100 cm⁻¹ spectral range. Perturbations of the lowest vibrational levels of the C state were localised and their origin discussed. A set of Dunham coefficients was deduced to fit the unperturbed levels of the C<span><math><mrow><msup><mrow></mrow><mrow><mn>1</mn></mrow></msup><msub><mrow><mi>Π</mi></mrow><mrow><mi>u</mi></mrow></msub></mrow></math></span> state with <span><math><mrow><mn>0</mn><mo>≤</mo><mi>v</mi><mo>≤</mo><mn>38</mn></mrow></math></span> and <span><math><mrow><mn>18</mn><mo>≤</mo><mi>J</mi><mo>≤</mo><mn>101</mn></mrow></math></span> and the potential energy curve of the state was constructed.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140619247","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}

{"title":"A new look at N2+ electronic transitions: An experimental and theoretical study","authors":"Laiz R. Ventura,&nbsp;Ramon S. da Silva,&nbsp;Jayr Amorim,&nbsp;Carlos E. Fellows","doi":"10.1016/j.jms.2024.111902","DOIUrl":"10.1016/j.jms.2024.111902","url":null,"abstract":"<div><p>Neutral and ionic N₂ species exhibit a rich spectrum as a result of the large density of couplings between states with different multiplicities. In this sense, spectra of the molecular ion N<span><math><msubsup><mrow></mrow><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math></span> are investigated combining Fourier transform spectroscopy and <em>ab initio</em> methods. We have reanalyzed the First Negative band System (B<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msubsup><mrow><mi>Σ</mi></mrow><mrow><mi>u</mi></mrow><mrow><mo>+</mo></mrow></msubsup></mrow></math></span> <span><math><mo>→</mo></math></span> X<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msubsup><mrow><mi>Σ</mi></mrow><mrow><mi>g</mi></mrow><mrow><mo>+</mo></mrow></msubsup></mrow></math></span>) including five bands not reported previously by Fourier spectroscopy. The spectra were recorded using a resolution of 0.6 cm⁻¹ and accuracy of 0.005 cm⁻¹. These results are then compared with new MRCI+Q/AV6Z calculations. For the first time, transition probabilities are computed for the previously observed 2<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>Π</mi></mrow><mrow><mi>g</mi></mrow></msub></mrow></math></span>-A<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>Π</mi></mrow><mrow><mi>u</mi></mrow></msub></mrow></math></span> band system. The 2<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>Π</mi></mrow><mrow><mi>g</mi></mrow></msub></mrow></math></span> state (<span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> = 67,029 cm⁻¹) has a dissociation energy of 24,787 cm⁻¹ at <span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> = 2.7332 a₀. The predicted lifetimes for the 2<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>Π</mi></mrow><mrow><mi>g</mi></mrow></msub></mrow></math></span>-A<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>Π</mi></mrow><mrow><mi>u</mi></mrow></msub></mrow></math></span> emissions are of the order of 170 ns. The calculated transition probabilities A(<span><math><msup><mrow><mi>v</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span>=0, <span><math><msup><mrow><mi>v</mi></mrow><mrow><mo>′</mo><mo>′</mo></mrow></msup></math></span>=0) for the B<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msubsup><mrow><mi>Σ</mi></mrow><mrow><mi>u</mi></mrow><mrow><mo>+</mo></mrow></msubsup></mrow></math></span>-X<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msubsup><mrow><mi>Σ</mi></mrow><mrow><mi>g</mi></mrow><mrow><mo>+</mo></mrow></msubsup></mrow></math></span> and 2<span><math><mrow><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>Π</mi></mrow><mrow><mi>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140407162","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}

{"title":"Predicting the rotational dependence of line broadening using machine learning","authors":"Elizabeth R. Guest,&nbsp;Jonathan Tennyson,&nbsp;Sergei N. Yurchenko","doi":"10.1016/j.jms.2024.111901","DOIUrl":"https://doi.org/10.1016/j.jms.2024.111901","url":null,"abstract":"<div><p>Correct pressure broadening is essential for modelling radiative transfer in atmospheres, however data are lacking for the many exotic molecules expected in exoplanetary atmospheres. Here we explore modern machine learning methods to mass produce pressure broadening parameters for a large number of molecules in the ExoMol data base. To this end, state-of-the-art machine learning models are used to fit to existing, empirical air-broadening data from the HITRAN database. A computationally cheap method for large-scale production of pressure broadening parameters is developed, which is shown to be reasonably (69%) accurate for unseen active molecules. This method has been used to augment the previously insufficient ExoMol line broadening diet, providing air-broadening data for all ExoMol molecules, so that the ExoMol database has a full and more accurate treatment of line broadening. Suggestions are made for improved air-broadening parameters for species present in atmospheric databases.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022285224000286/pdfft?md5=bb9e0d35ca6f02e39044595f28bd089d&pid=1-s2.0-S0022285224000286-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140180150","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}

{"title":"Spectroscopic observation and ab initio calculations of a new isomer of the CS2 trimer","authors":"A.J. Barclay ,&nbsp;A.R.W. McKellar ,&nbsp;A. Pietropolli Charmet ,&nbsp;N. Moazzen-Ahmadi","doi":"10.1016/j.jms.2024.111899","DOIUrl":"https://doi.org/10.1016/j.jms.2024.111899","url":null,"abstract":"<div><p>We report spectroscopic observation and theoretical calculations of a new isomer of (CS₂)₃ as observed in the regions of the ν₃ fundamental band of CS₂ (6.5 μm) and the ν₁ + ν₃ combination band (4.5 μm), using tunable laser sources and a pulsed supersonic slit-jet. The previously observed CS₂ trimer has a barrel-shaped structure with three equivalent monomers and <em>D</em>₃ symmetry. The new isomer consists of a staggered parallel “dimer pair” of equivalent CS₂ monomers with a third CS₂ monomer sitting “on top”, similar to the known non-cyclic CO₂ trimer. This structure has <em>C</em>₂ rotational symmetry corresponding to the <em>b</em> inertial axis of the trimer, as proven by observed nuclear spin statistics. <em>Ab initio</em> calculations correctly give the two observed isomer structures and indicate that they lie very close in binding energy.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022285224000262/pdfft?md5=e2866be731d3b8c41008cac8033764e3&pid=1-s2.0-S0022285224000262-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140103872","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}

{"title":"Laboratory rotational spectroscopy of the magnesium-carbon chains MgC4H and MgC3N","authors":"P. Bryan Changala ,&nbsp;Nadav Genossar-Dan ,&nbsp;Joshua H. Baraban ,&nbsp;Michael C. McCarthy","doi":"10.1016/j.jms.2024.111904","DOIUrl":"https://doi.org/10.1016/j.jms.2024.111904","url":null,"abstract":"<div><p>Recent advances in circumstellar metal chemistry and laser-coolable molecules have spurred interest in the spectroscopy and electronic properties of alkaline earth metal-bearing polyatomic molecules. We report the microwave rotational spectra of two members of this important chemical family, the linear magnesium-carbon chains MgC<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>H and MgC<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>N, detected with cavity Fourier transform microwave spectroscopy of a laser ablation-electric discharge expansion. The rotation, fine, and hyperfine parameters have been derived from the precise laboratory rest frequencies. These experimental results, combined with a theoretical quantum chemical analysis, confirm the recent identification of MgC<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>H and MgC<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>N in the circumstellar envelope of the evolved carbon-rich star IRC+10216. The spectroscopic data also provide insight into the structural and electronic properties that influence the metal-based optical cycling center in this unique class of laser-coolable polyatomics.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140604833","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}

{"title":"Measurements of infrared absorption cross-sections for n-C3F8, c-C4F8, n-C4F10, and n-C5F12 from 298 to 350 K","authors":"Muhammad Osama Ishtiak ,&nbsp;Orfeo Colebatch ,&nbsp;Karine Le Bris ,&nbsp;Paul J. Godin ,&nbsp;Kimberly Strong","doi":"10.1016/j.jms.2024.111900","DOIUrl":"10.1016/j.jms.2024.111900","url":null,"abstract":"<div><p>Perfluoro-n-propane, perfluorocyclobutane, perfluoro-n-butane, and perfluoro-n-pentane are non-ozone-depleting industrial alternatives to chlorofluorocarbons and hydrochlorofluorocarbons. However, these perfluoroalkanes have significant band strength in the atmospheric window from 800 to 1200 cm⁻¹. Coupled with their millennial-scale atmospheric lifetimes, they can lead to significant long-term global warming. Infrared spectra are required to quantify the climate impacts. This work provides a set of high-temperature infrared absorption cross-sections in the range 298–350 K at 0.1 cm⁻¹ resolution from 515 to 1500 cm⁻¹ for each compound. Our cross-sections generally agree with literature measurements except for perfluoro-n-pentane. We use density functional theory to calculate the absorption cross-sections from 0 to 515 cm⁻¹ using the B3LYP functional and several basis sets. The 6-31G(d,p) basis set provides the best results for linear perfluoroalkanes, while the def2-TZVP basis set provides the best results for cyclic perfluoroalkanes. Using experimental cross-sections, we calculate the radiative efficiency and global warming potential for each compound, utilizing the Pinnock curve from Shine and Myhre (2020) and atmospheric lifetimes from Hodnebrog et al. (2020). These quantities are found to be independent of temperature. The average 100-year global warming potential derived from all cross-sections is 9,610±1,260, 10,800±1,420, 10,100±1,330, and 9,380±1,230 for perfluoro-n-propane, perfluorocyclobutane, perfluoro-n-butane, and perfluoro-n-pentane, respectively. Combining the data in this work with our previous measurements reveals that the global warming potential for perfluoroalkanes with an increasing number of C<img>F bonds depends on the ratio of radiative efficiency to molecular weight.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022285224000274/pdfft?md5=1606f942c2fb317c06570494fb3fba8f&pid=1-s2.0-S0022285224000274-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140154167","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}

{"title":"Vibrational spectroscopy of aniline cations and their H-loss cations in helium droplets","authors":"Arisa Iguchi ,&nbsp;Amandeep Singh ,&nbsp;Susumu Kuma ,&nbsp;Hajime Tanuma ,&nbsp;Toshiyuki Azuma","doi":"10.1016/j.jms.2024.111903","DOIUrl":"10.1016/j.jms.2024.111903","url":null,"abstract":"<div><p>We produced aniline cations (<span><math><mi>c</mi></math></span>–C₆H₅ <img>NH₂⁺) and their dehydro- (H-loss) cations inside helium droplets by electron ionization and observed their mass-selected vibrational spectra in the N<img>H stretching region. We observed vibrational bands at <em>m/q</em> = 93 which were identified as aniline cations. These bands showed only a few cm⁻¹ shifts from the symmetric and anti-symmetric N<img>H stretching bands for the amino (<img>NH₂) group in the gas phase. For the H-loss cation at mass <em>m/q</em> = 92, the agreement of the observed N<img>H band frequency with the result of DFT calculations suggests several candidate species, including a seven-membered ring structure, 4-monodehydro azepinylium (<span><math><mi>c</mi></math></span>–C₆NH₆⁺). A new reaction pathway to this cation was discussed by considering large excess energy in the ionization process.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140398430","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}

{"title":"Rotational detection of the silicon-carbon chains H2C3Si and HSiCCH","authors":"Michael C. McCarthy,&nbsp;P. Bryan Changala,&nbsp;P. Brandon Carroll","doi":"10.1016/j.jms.2024.111886","DOIUrl":"10.1016/j.jms.2024.111886","url":null,"abstract":"<div><p>The rotational spectra of two new silicon-bearing carbon chains, H₂C₃Si and HSiCCH have been detected by means of Fourier-transform microwave spectroscopy in a supersonic jet source equipped with an electrical discharge. On the basis of measurements between 10 and 42<!--> <!-->GHz, precise spectroscopic constants have been determined for both molecules. Along with H²⁹SiCCH and H³⁰SiCCH, which were detected in natural abundance, several other rare isotopic species of HSiCCH were observed using samples enriched in carbon-13 and D. From this isotopic data, a precise semi-experimental equilibrium structure was derived and compared with a re-evaluated semi-experimental equilibrium structure of the parent silylene SiH₂; the deuterium isotopic measurements also provide important clues as to the formation pathway of HSiCCH in our discharge. Because other small Si-bearing chains have been detected in the circumstellar envelope of the evolved carbon star IRC+10216, both chains may be of astronomical interest.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139557719","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}

{"title":"Diborane anharmonic vibrational frequencies and Intensities: Experiment and theory","authors":"Aaron I. Strom ,&nbsp;Ibrahim Muddasser ,&nbsp;Guntram Rauhut ,&nbsp;David T. Anderson","doi":"10.1016/j.jms.2024.111887","DOIUrl":"https://doi.org/10.1016/j.jms.2024.111887","url":null,"abstract":"<div><p>The vibrational dynamics of diborane have been extensively studied both theoretically and experimentally ever since the bridge structure of diborane was established in the 1950s. Numerous infrared and several Raman spectroscopic studies have followed in the ensuing years at ever increasing levels of spectral resolution. In parallel, <em>ab initio</em> computations of the underlying potential energy surface have progressed as well as the methods to calculate the anharmonic vibration dynamics beyond the double harmonic approximation. Nevertheless, even 70 years after the bridge structure of diborane was established, there are still significant discrepancies between experiment and theory for the fundamental vibrational frequencies of diborane. In this work we use parahydrogen (pH₂) matrix isolation infrared spectroscopy to characterize six fundamental vibrations of B₂H₆ and B₂D₆ and compare them with results from configuration-selective vibrational configuration interaction theory. The calculated frequencies and intensities are in very good agreement with the pH₂ matrix isolation spectra, even several combination bands are well reproduced. We believe that the reason discrepancies have existed for so long is related to the large amount of anharmonicity that is associated with the bridge BH stretching modes. However, the calculated frequencies and intensities reported here for the vibrational modes of all three boron isotopologues of B₂H₆ and B₂D₆ are within ± 2.00 cm⁻¹ and ± 1.44 cm⁻¹, respectively, of the experimental frequencies and therefore a refined vibrational assignment of diborane has been achieved.</p></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139733136","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}