Journal of Molecular Spectroscopy最新文献

{"title":"Microwave spectra of jet-cooled bromo- and chloroacetic acids","authors":"Kenneth J. Koziol,&nbsp;Aaron J. Reynolds,&nbsp;Victor Drewanz,&nbsp;Luis R. Padilla Jr.,&nbsp;Kenneth R. Leopold","doi":"10.1016/j.jms.2025.112033","DOIUrl":"10.1016/j.jms.2025.112033","url":null,"abstract":"<div><div>Microwave spectra of jet-cooled bromoacetic acid (CH₂BrCOOH) and chloroacetic acid (CH₂ClCOOH) have been obtained. For bromoacetic acid, the observed spectra are definitively assigned to a conformer in which the C–Br bond is nearly perpendicular to the plane defined by the other heavy atoms. This differs from the conformer previously observed at room temperature in which the C–Br bond was found to be <em>in the plane</em>. MP2 and DFT calculations predict four stable conformations, and the observed form corresponds to that with the lowest calculated energy. Diagonal and off-diagonal elements of the ⁷⁹Br and ⁸¹Br nuclear quadrupole coupling tensors have been determined and are in good agreement with the calculations. Interestingly, previous room temperature work on chloroacetic acid also revealed the conformation in which the C–Cl bond is in-plane (i.e., analogous to the room temperature work on bromoacetic acid). Thus, to see if the same disparity exists between the conformers observed under room temperature and jet-cooled conditions, the spectrum of jet-cooled chloroacetic was also examined. In this case, the conformer observed in the jet was the <em>same</em> as that previously reported at room temperature (in-plane C–Cl bond). The spectroscopic constants obtained, however, are somewhat more accurate than those previously determined and are reported here. Due to the cooling in the supersonic expansion, the species observed in this work are likely the lowest-energy forms for both acids. Comparison with prior studies on fluoro-, chloro-, and bromoacetic acids highlights a complex conformational landscape for these systems.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"411 ","pages":"Article 112033"},"PeriodicalIF":1.4,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144653280","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":"Exploring indole dimer structures at the band origin: A spectroscopic gas phase IR analysis","authors":"Saurabh Mishra","doi":"10.1016/j.jms.2025.112031","DOIUrl":"10.1016/j.jms.2025.112031","url":null,"abstract":"<div><div>Non-covalent interactions such as hydrogen bonding and π–π stacking are central to molecular architecture. This study investigates the indole dimer near the band origin at 35238 cm⁻¹ using IR-UV double resonance spectroscopy and DFT calculations. The IDIR spectrum shows a red-shifted N<img>H stretch at 3420 cm⁻¹, indicative of hydrogen bonding. Computational analyses with B97D and B3LYP-D3 functionals favor N–H‧‧‧π bonded structures. Among these, we assign a tilted geometry featuring N–H‧‧‧π interaction as the most consistent with experimental observations. The broad spectral profile also suggests the coexistence of multiple low-energy isomers.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"411 ","pages":"Article 112031"},"PeriodicalIF":1.4,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144611716","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":"Deperturbation analysis of an avoided crossing in the A1 v = 0 and B1 v = 0 states of WO","authors":"Kristin N. Bales ,&nbsp;Akhila Swarna ,&nbsp;James J. O'Brien ,&nbsp;Leah C. O'Brien","doi":"10.1016/j.jms.2025.112022","DOIUrl":"10.1016/j.jms.2025.112022","url":null,"abstract":"<div><div>The (0,0) and (0,1) bands of the A1 – X0⁺ and B1 – X0⁺ transitions of tungsten monoxide (WO) have been recorded in high resolution using intracavity laser absorption spectroscopy techniques (ILS and ILS-FTS). Lines for all four abundant isotopologues, ¹⁸²WO, ¹⁸³WO, ¹⁸⁴WO, and ¹⁸⁶WO, are observed and have been rotationally analyzed and fit using a constrained-variables approach in PGOPHER. While these transitions have been previously described in the literature, this new analysis incorporates all four isotopologues and presents e<em>v</em>idence for an avoided crossing interaction between the v = 0 vibrational levels of the A1 and B1 states. New values for spectroscopic constants that incorporate the perturbation interactions are presented and compared to literature results.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"410 ","pages":"Article 112022"},"PeriodicalIF":1.4,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144196135","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 molecular beam study of the (0,0)A2Π←X2Σ+ band of CaF isotopologues","authors":"Termeh Bashiri ,&nbsp;Phelan Yu ,&nbsp;Nicholas R. Hutzler ,&nbsp;Timothy C. Steimle ,&nbsp;Carlos Abad ,&nbsp;Mitchio Okumura","doi":"10.1016/j.jms.2025.112023","DOIUrl":"10.1016/j.jms.2025.112023","url":null,"abstract":"<div><div>This study presents an experimental determination of spectroscopic parameters for the less-abundant isotopologues ⁴²CaF and ⁴⁴CaF, alongside ⁴⁰CaF, by high resolution laser-induced fluorescence spectroscopy in a skimmed free jet expansion. We recorded spectra near the natural linewidth limit and derived spectroscopic constants for both <span><math><mrow><msup><mrow><mi>X</mi></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><mi>A</mi></mrow><mrow><mn>2</mn></mrow></msup><mi>Π</mi></mrow></math></span> states, including the fine and ¹⁹F magnetic hyperfine parameters. We also estimated the <em>r</em>(⁴⁴Ca/⁴⁰Ca) isotope amount ratio, demonstrating the potential use of optical spectroscopy for isotope analysis.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"410 ","pages":"Article 112023"},"PeriodicalIF":1.4,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144470219","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":"Impact of the metal ion and microsolvation on the structure and vibrations in a small model peptide","authors":"K.A.E. Meyer,&nbsp;E. Garand","doi":"10.1016/j.jms.2025.112021","DOIUrl":"10.1016/j.jms.2025.112021","url":null,"abstract":"<div><div>The impact of alkali metal ions (Li⁺, Na⁺, and K⁺) on the structure and vibrations in metal ion-diglycine complexes with up to two water molecules (M⁺GlyGly-<em>n</em>H₂O) is examined using cryogenic infrared action spectroscopy, conformer-specific IR-IR spectroscopy, H₂O/D₂O isotopic substitution experiments, and scaled, harmonic DFT calculations. While the main conformer is identical for all metal ions for the bare complex (M⁺GlyGly), the conformers observed upon the addition of water are dependent on the nature of the metal ion and the impact of solvation is distinctly larger for the Li⁺ than for the K⁺ ion. The number of solvent molecules needed to change the initial peptide conformation differs between the metal ions and is smaller for Li⁺ than for the larger metal ions. The comparison of the spectra upon the sequential addition of water reveals how solvation impacts the electric field strength of the metal ions in these clusters. In all cases, the addition of water molecules reduces the strength of the interaction between the metal ion and the peptide and consequently, reduces the strength of the electric field induced in the peptide.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"410 ","pages":"Article 112021"},"PeriodicalIF":1.4,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144168695","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":"Theoretical study on the low-lying electronic states of SbF","authors":"Zhuozhao Li ,&nbsp;Linqiao Guo ,&nbsp;Lei Zhang ,&nbsp;Kai Wang ,&nbsp;Wenli Zou","doi":"10.1016/j.jms.2025.112011","DOIUrl":"10.1016/j.jms.2025.112011","url":null,"abstract":"<div><div>Multi-reference configuration interaction calculations are carried out to elucidate the distribution of low-lying valence and Rydberg states of antimony monofluoride (SbF) below 50000 cm⁻¹, where the effects of core–valence correlation and spin–orbit coupling have been employed. From the potential energy curves, the spectroscopic constants of seven (quasi-)bound <span><math><mi>Λ</mi></math></span>-S and fourteen (quasi-)bound <span><math><mi>Ω</mi></math></span> states have been derived, which agree well with the experimental values. Our results show that the second <span><math><mrow><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup><mi>Π</mi></mrow></math></span> state involves the occupation on the Rydberg shell 6<span><math><mi>s</mi></math></span> of Sb, which settles the assignment of the so-called “<span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>” and “<span><math><mrow><msub><mrow><mi>C</mi></mrow><mrow><mn>3</mn></mrow></msub><mn>1</mn></mrow></math></span>” states in the ultraviolet spectra of SbF. With the help of the more accurate coupled cluster calculations, the dissociation energy (<span><math><msub><mrow><mi>D</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span>) of SbF is determined to be 4.24 eV at the theoretical limit, being 0.2 eV smaller than the widely used empirical value in the literature.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"410 ","pages":"Article 112011"},"PeriodicalIF":1.4,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143830243","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":"New spectroscopic fits and ab initio study of the O2(Σg−3)-SO2 (1A1) open-shell dimer","authors":"Wafaa M. Fawzy","doi":"10.1016/j.jms.2025.112010","DOIUrl":"10.1016/j.jms.2025.112010","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We report the first accurate global fits for the rotation-spin-tunneling transitions in the microwave spectrum of the O&lt;sub&gt;2&lt;/sub&gt;(&lt;span&gt;&lt;math&gt;&lt;mmultiscripts&gt;&lt;msubsup&gt;&lt;mi&gt;Σ&lt;/mi&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;mprescripts&gt;&lt;/mprescripts&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mmultiscripts&gt;&lt;/math&gt;&lt;/span&gt;)-SO&lt;sub&gt;2&lt;/sub&gt; (&lt;sup&gt;1&lt;/sup&gt;A&lt;sub&gt;1&lt;/sub&gt;) weakly bonded open-shell complex. In addition, we present a new ab initio investigation of the potential energy surface of O&lt;sub&gt;2&lt;/sub&gt;(&lt;span&gt;&lt;math&gt;&lt;mmultiscripts&gt;&lt;msubsup&gt;&lt;mi&gt;Σ&lt;/mi&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;mprescripts&gt;&lt;/mprescripts&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mmultiscripts&gt;&lt;/math&gt;&lt;/span&gt;)-SO&lt;sub&gt;2&lt;/sub&gt;, using the UCCSD(T)/aug-cc-pV(n + d)Z level of theory where &lt;em&gt;n&lt;/em&gt; = 2 and 3. Analysis of the spectrum identified a-type and c-type transitions, frequencies of the a-type were not shifted while those of the c-type were shifted due to tunneling of the O&lt;sub&gt;2&lt;/sub&gt; and the SO&lt;sub&gt;2&lt;/sub&gt; moieties in the dimer. Only the A&lt;sub&gt;1&lt;/sub&gt; symmetric tunneling state was detected because the antisymmetric A&lt;sub&gt;2&lt;/sub&gt; state is not allowed by nuclear spin statistics in O&lt;sub&gt;2&lt;/sub&gt;-SO&lt;sub&gt;2&lt;/sub&gt;. Least squares fits with a standard deviation of 1 kHz were obtained using two computer codes incorporating semi-rigid rotor Hamiltonians that employ two different angular momenta coupling schemes. Results of the fits determined the effective tunneling frequency in the A&lt;sub&gt;1&lt;/sub&gt; symmetric state as &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;ν&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;= 2373.61134 &lt;span&gt;&lt;math&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;16 MHz, the electron spin coupling constant λ = 42,870.2186 &lt;span&gt;&lt;math&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;43 MHz, the rotational constants A = 7099.44 &lt;span&gt;&lt;math&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;33, B = 1528.886 &lt;span&gt;&lt;math&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;5, C = 1763.36 &lt;span&gt;&lt;math&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;6 MHz. The value of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;ν&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; equals the tunneling splitting (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) between the&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; symmetric tunneling states in the dimer, where the&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; levels are shifted in energy by &lt;span&gt;&lt;math&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mfrac&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mfrac&gt;&lt;msub&gt;&lt;mi&gt;ν&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mfrac&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mfrac&gt;&lt;msub&gt;&lt;mi&gt;ν&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, respectively. The ab initio study identified a global minimum energy structure of C&lt;sub&gt;1&lt;/sub&gt; symmetry and a metastable local minimum of C&lt;sub&gt;s&lt;/sub&gt; symmetry. We computed the optimized geometries of four equivalent configurations in the m","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"409 ","pages":"Article 112010"},"PeriodicalIF":1.4,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820648","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":"Analysis of the rotational and hyperfine structure in the ‘red’ bands of ruthenium monoxide (RuO)","authors":"G.M. Chenard ,&nbsp;A.G. Adam ,&nbsp;D.W. Tokaryk ,&nbsp;C. Linton","doi":"10.1016/j.jms.2025.112007","DOIUrl":"10.1016/j.jms.2025.112007","url":null,"abstract":"<div><div>Laser Induced Fluorescence has been used to study the spectroscopy of Ruthenium Monoxide (RuO) in the UNB laser-ablation molecular-jet apparatus. High-resolution spectra of six bands from four previously obtained electronic transitions, [16.05]5 – X⁵Δ₄, [16.19]4 - X⁵Δ₄, [16.19]4 - X⁵Δ₃ and [15.07]3 - X⁵Δ₄ plus two previously unobserved transitions, [15.70]3 and [16.36]3 – X⁵Δ₄, were obtained at a resolution 20 times higher than previous experiments. This enabled rotational structure of six individual RuO isotopologues, ⁹⁶RuO, ⁹⁹RuO, ¹⁰⁰RuO, ¹⁰¹RuO, ¹⁰²RuO and ¹⁰⁴RuO to be well resolved and was used to examine detailed rotational and vibrational isotope effects. Hyperfine structure due to the nuclear spin <em>I</em> = 5/2 of ⁹⁹Ru and ¹⁰¹Ru has also been well resolved and was a valuable aid in establishing the electron configurations of the electronic states. The difference in the hyperfine structure in the [16.05]5 and [16.19]4 states supported their assignment as the Ω = 5 and 4 spin orbit components, ⁵Φ₅ and ⁵Φ₄, of a single Hund's case (a) electronic state.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"409 ","pages":"Article 112007"},"PeriodicalIF":1.4,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143746746","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":"Oscillator strengths of the fundamental and overtone OH-stretching bands of tert-butyl hydroperoxide in gas phase","authors":"Casper Vindahl Jensen,&nbsp;Emil Vogt,&nbsp;Henrik G. Kjaergaard","doi":"10.1016/j.jms.2025.112009","DOIUrl":"10.1016/j.jms.2025.112009","url":null,"abstract":"<div><div>We have recorded gas-phase room-temperature absorption spectra of <em>t</em>-BuOOH in the OH-stretching regions, <span><math><mrow><mi>Δ</mi><msub><mrow><mi>v</mi></mrow><mrow><mi>O</mi><mi>H</mi></mrow></msub><mo>=</mo><mn>1</mn><mo>−</mo><mn>5</mn></mrow></math></span>, using a combination of Fourier transform infrared spectroscopy and cavity ring-down spectroscopy. The <em>t</em>-BuOOH samples are phase-extracted into dichloromethane, which can be accurately accounted for by spectral subtraction. We thereby obtain spectra of pure <em>t</em>-BuOOH and corresponding sample partial pressures allowing us to obtain absolute intensities of the OH-stretching bands in all regions. The subtraction of solvents and impurities provides accurate values for the band intensities and positions. A reduced dimensional local mode model is invoked to corroborate the experimentally determined band oscillator strengths and their assignments. The fundamental OH-stretching band oscillator strength is determined to be <span><math><mrow><mrow><mo>(</mo><mn>4</mn><mo>.</mo><mn>56</mn><mo>±</mo><mn>0</mn><mo>.</mo><mn>15</mn><mo>)</mo></mrow><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>6</mn></mrow></msup></mrow></math></span> about twice as large as the literature value. In the <span><math><mrow><mi>Δ</mi><msub><mrow><mi>v</mi></mrow><mrow><mi>O</mi><mi>H</mi></mrow></msub><mo>=</mo><mn>5</mn></mrow></math></span> region, the intensity is spread out efficiently by a Franck–Condon-like mechanism to combination features associated with the OH-stretch and the COOH-torsion.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"409 ","pages":"Article 112009"},"PeriodicalIF":1.4,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143776793","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":"Two codes for calculation of the rotation-spin-tunneling energy levels in the microwave and the infrared spectra of O2 (Σg-3)-XY2 open-shell complexes","authors":"Wafaa M. Fawzy","doi":"10.1016/j.jms.2025.112008","DOIUrl":"10.1016/j.jms.2025.112008","url":null,"abstract":"<div><div>We developed new FORTRAN codes that employ two different Hamiltonians [Wafaa M. Fawzy, J. Mol. Spectrosc., 397, 111,822, 2023] for calculation of energy levels and relative intensities of rotational transitions in an asymmetric or a symmetric top weakly-bonded open-shell dimer. The type of complexes of interest consist of a polyatomic/diatomic closed-shell molecule and the O₂ diradical in its ground electronic state, where the monomers experience rotation-tunneling motion. The programs set up the Hamiltonian matrix considering pure rotation, quartic and sextic centrifugal distortion terms, electron-spin electron-spin coupling, R-dependence of electron-spin constants, electron-spin-rotation interaction, a symmetry treatment for rotation-tunneling of the monomers, and dependence of the rotational constants on the rotation-tunneling state. Numerical diagonalization of the total Hamiltonian matrix in the molecular basis set provides the eigenvalues and the eigenfunctions. The eigenfunctions are used to transform expectation values of the parity, five quantum numbers (&lt;P&gt;, &lt;K&gt;, &lt;N&gt;, &lt;P_s&gt;, &lt;Σ&gt;), and the electric dipole moment matrix elements from the Hamiltonian basis set to the eigenfunctions basis of the complex. Calculations showed that goodness of the quantum numbers depends on geometry and relative values of the electron–spin electron–spin coupling constants, the rotational parameters, the tunneling splitting. We used the Hellman–Feynman theory for calculation of derivatives of the eigenvalues with respect to molecular parameters, which significantly reduces the computer time for the non-linear least squares fits of transitions. The FORTRAN suites of computer programs were tested and validated by fitting the high resolution IR and MW spectra of the O₂–DF and the O₂-SO₂ dimers, respectively, with standard deviations within accuracy of the frequency measurement. However, the codes should be suitable for spectral analysis of any O₂ -XY₂ or O₂ -XY cluster, where XY₂ and XY represent a closed-shell non-linear triatomic molecule of C₂v symmetry (e.g. H₂O) and a diatomic entity (e.g. CO), respectively. The FORTRAN source programs, input and output files for spectral fits of the MW spectrum of O₂-SO₂ are discussed. In addition, zipped files of the suites of programs, the input and output files for fitting the MW spectrum of O₂-SO₂ and the IR spectrum of O₂ -DF, respectively, are provided as supplements that can be downloaded.</div></div>","PeriodicalId":16367,"journal":{"name":"Journal of Molecular Spectroscopy","volume":"409 ","pages":"Article 112008"},"PeriodicalIF":1.4,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143817609","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}