{"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":null,"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 O<sub>2</sub> 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 (<P>, <K>, <N>, <P<sub>s</sub>>, <Σ>), 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 O<sub>2</sub>–DF and the O<sub>2</sub>-SO<sub>2</sub> dimers, respectively, with standard deviations within accuracy of the frequency measurement. However, the codes should be suitable for spectral analysis of any O<sub>2</sub> -XY<sub>2</sub> or O<sub>2</sub> -XY cluster, where XY<sub>2</sub> and XY represent a closed-shell non-linear triatomic molecule of C<sub>2</sub>v symmetry (e.g. H<sub>2</sub>O) and a diatomic entity (e.g. CO), respectively. The FORTRAN source programs, input and output files for spectral fits of the MW spectrum of O<sub>2</sub>-SO<sub>2</sub> are discussed. In addition, zipped files of the suites of programs, the input and output files for fitting the MW spectrum of O<sub>2</sub>-SO<sub>2</sub> and the IR spectrum of O<sub>2</sub> -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":1.4000,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Molecular Spectroscopy","FirstCategoryId":"101","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0022285225000244","RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"PHYSICS, ATOMIC, MOLECULAR & CHEMICAL","Score":null,"Total":0}
引用次数: 0
Abstract
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 (<P>, <K>, <N>, <Ps>, <Σ>), 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.
期刊介绍:
The Journal of Molecular Spectroscopy presents experimental and theoretical articles on all subjects relevant to molecular spectroscopy and its modern applications. An international medium for the publication of some of the most significant research in the field, the Journal of Molecular Spectroscopy is an invaluable resource for astrophysicists, chemists, physicists, engineers, and others involved in molecular spectroscopy research and practice.