Sökning: "vibrational modes"

Visar resultat 1 - 5 av 62 avhandlingar innehållade orden vibrational modes.

  1. 1. Low-Energy Modes of Molecules and Atoms Chemisorbed on a Metal Surface. CO and O on Pt(111) Studied by Infrared Spectroscopy

    Författare :Ulrika Engström; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; dipole-allowed modes; low-energy modes; carbon monoxide; Infrared spectroscopy; dipole-forbidden modes; Pt 111 ; anti-absorption; Fermi resonance; atomic oxygen;

    Sammanfattning : This thesis is devoted to the investigation of low-energy metal-adsorbate vibrational modes of CO molecules and O atoms chemisorbed on a Pt(111) surface using infrared spectroscopy (IRS). The infrared selection rule states that only vibrational modes having a non-vanishing component of its dynamical dipole moment perpendicular to the surface can be directly excited using IRS, known as dipole-allowed modes. LÄS MER

  3. 2. Understanding the interactions between vibrational modes and excited state relaxation in garnet structured phosphors

    Författare :Yuan-Chih Lin; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; free electron laser; thermal quenching.; luminescence; garnet; vibrational spectroscopy; neutron scattering; phosphor; light emitting diode;

    Sammanfattning : This thesis concerns investigations of the local structural environments and vibrational dynamics of the three garnet type oxide phosphors Ce3+-doped Y3Al5O12 (YAG:Ce3+), Ca3Sc2Si3O12 (CSS:Ce3+), and Sr3Y2Ge3O12 (SYG:Ce3+), which show promising optical properties as luminescent materials used in solid state white lighting technologies. The study focuses on a comprehensive analysis of the nature of the long-range vibrations (phonons) in terms of local atomic and molecular motions of the garnet structure, as well as their dependence on the nature of the garnet chemical composition, Ce3+ concentration and temperature. LÄS MER

  4. 3. Structure-Specific Vibrational Modes of Isolated Biomolecules Studied with Mid- and Far-Infrared Laser Spectroscopy

    Författare :Vasyl Yatsyna; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; far-infrared gas-phase spectroscopy; conformers; vibrational anharmonicity; infrared multiple photon dissociation; peptide structure; folded and extended peptides; hydrogen bonding;

    Sammanfattning : Biomolecular structure elucidation is crucial for our detailed understanding of various biological processes, since there is an intimate relationship between the biomolecular function and structure. In this respect, isolated biomolecules, despite being outside of their natural environment, are perfect model systems for in-depth studies of various fundamental interactions that govern the formation of biomolecular structure. LÄS MER

  5. 4. Surface Vibrational and Electron Spectroscopy - Experiments and first-principle calculations

    Författare :Martin Andersson; Kemisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; gränsskikt; anharmonicity; Ytkemi; Surface and boundary layery chemistry; adsorbates; metal surface; density functional theory; first-principle calculations; electron spectroscopy; reflection-absorption infrared spectroscopy; vibrational spectroscpy;

    Sammanfattning : This work deals with interpretation of experimental surface spectroscopic data with the aid of first-principle calculations. Surface infrared reflection-absorption spectra as well as spectra from the electron spectroscopic methods photoemission and X-ray absorption are considered. LÄS MER

  7. 5. Vibrational Spectroscopy of Surface Adsorbates on Metal Surfaces. Experiments and Calculations

    Författare :Ragnar K Ásmundsson; Kemisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; ab initio electronic structure calculations; Fermi resonance; vibrational spectroscopy; Reflection absorption infrared spectroscopy; Fourier transform infrared spectroscopy; Cu 100 and W 110 single crystal surfaces; Physics; Fysik;

    Sammanfattning : This work deals with a detailed analysis of the vibrational spectra of methoxy (CH3O-) and ethoxy (CH3CH2O-) on W(110) and Cu(100) single crystal surfaces. By using theoretical ab initio quantum mechanical modeling, it is demonstrated that an unprecedented quantitative understanding of the vibrational frequencies of a surface adsorbate can be obtained. LÄS MER