<i>Vibration Spectra and Symmetry of Crystals</i>

Poulet, H.; Mathieu, Jean‐Paul; Klein, Miles V.

doi:10.1063/1.2995144

Cited by 49 publications

(51 citation statements)

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“…Reflectance bands in the MIR from 10 µm to 25 µm (1000 to 400 cm −1 ) are the so-called fundamental vibrational modes (Poulet & Mathieu 1976) that can be divided into internal stretching, bending and librating of the SiO 4 group. In the short wavelength infrared (SWIR) region roughly between 2.5 µm and 10 µm, reflectance peaks are mainly overtones and combinational bands of the fundamental lattice modes.…”

Section: Introductionmentioning

confidence: 99%

Optical spectroscopic characterizations of laser irradiated olivine grains

Yang

Zhang

Wang

et al. 2016

A&A

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Context. Visible and near-infrared spectra of asteroids are known to be susceptible to nanophase irons produced by space weathering processes, thus making mineral identifications difficult. Mid-infrared spectroscopy may retain more mineral features owing to its lattice vibrational nature. Aims. We investigate the structure and reflectance spectral feature changes of olivine grains before and after simulated space weathering. Methods. We irradiate olivine grains by using pulsed laser to simulate varying degrees of micrometeorite bombardments. Reflectance measurements from 0.5 to 25 µm and radiative transfer calculations were carried out in order to compare them with each other. Results. Both the experimental simulations and modeling results indicate that the mid-infrared spectral features of olivine grains can survive the intense irradiations. Although the Christansen Feature is slightly shifted to longer wavelength, major vibrational bands remain essentially unchanged, because the lattice structure is quite immune to even the strongest irradiations, as revealed by both the X-ray diffraction and Raman scattering measurements. Conclusions. Mid-infrared spectroscopy is much more immune to productions of nanophase irons and amorphous materials and thus may be used more reliably in remote detections of minerals on asteroid surfaces.

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Section: Introductionmentioning

confidence: 99%

Optical spectroscopic characterizations of laser irradiated olivine grains

Yang

Zhang

Wang

et al. 2016

A&A

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“…Como nenhuma nova reflexão foi observada acima de 4 GPa, até cerca de 6 GPa, e como todas as reflexões podem ser indexadas de acordo com a mesma simetria cúbica, uma análise dos subgrupos espaciais do grupo F43m sugere, como provável candidato a grupo de simetria da fase II, o grupo cúbico F23. Neste grupo, a simetria do sítio ocupado peloíon amônio seria 23 (T) e, portanto, não haveria splitting dos modo de bending ν 2 e ν 4 [71].…”

Section: B Transições De Fase Estruturais Em Alta Pressãounclassified

Pressure-induced Phase Transitions in Defect Pyrochlores

Prottoni¹,

Jornada²

2013

Sci. cum Ind.

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In this paper the influence of pressure and temperature on four compounds with defect pyrochlore structure (NH4NbWO6, RbNbWO6, CsNbWO6, and p-WO3) is explored by means of X-ray diffraction, vibrational (Raman and infrared absorption) spectroscopy and computer simulations. Several structural transitions were observed, including an unusual insertion reaction with volume increase at high pressures. This latter transition is further explored to reveal the influence on the transition pressure of the nature and ionic radius of the cation residing inside the cages formed by the pyrochlore framework. http://dx.doi.org/10.18226/23185279.v1iss1p24

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“…To first order, A may be considered a tensor of order 1 with three orthonormal vector components. In this form it is known as the electric dipole approximation (5,6). It cames with it the implication that, because of the relative sizes of the photon and molecule, the field is constant across the molecule.…”

Section: Coupling Of a Mass Body To A Photonmentioning

confidence: 99%

A vectorial model of photon–molecule interactions and the development of an Octupole Rule of vibrational excitation

Hollebone¹

1984

Can. J. Chem.

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An alternative approach to the assignment of molecular vibrations is suggested in which both the molecule and the photon are taken as coincident quantum mechanical entities at the instant of impulse. This model permits the description of the excitation in a simple vectorial form. Using subduction techniques, complete and orthonormal basis vectors for both particles can be defined and the probabilities of excitation are directly related to the overlap of these basis vectors at the instant of space and time coincidence. The model obeys fully the requirements of the 3n -6 degrees of freedom rule and is found to express the motions of atoms in terms of their overlap with available multipole fields of the photon. To first order the photon-molecule interaction is taken as the Coulomb potential between the electric fields of the photon and those of the shielded atomic nuclei. The relatively low valence electron density is ignored but becomes important in second order. With this assumption, molecular translational motion correlates to, and exhausts, the dipolar photon field, rotation corresponds to three of the five components of the photon quadrupole and ungerade internal modes are first permitted by overlap with the photon octupole. Some of the consequences of this Octupole Rule are discussed with particular reference to octahedral molecules from which molecules of lower symmetry can be algebraically subduced.B. R. HOLLEBONE. Can. J. Chem. 62, 2287 (1984.On suggkre une approche de rechange pour attribuer les vibrations molCculaires; dans cette approche, la moltcule et le photon sont considtrCs comme des entitCs de mCcanique quantique qui sont coincidentes au moment de l'impulsion. Ce modkle permet de dCcrire l'excitation sous une forme vectorielle simple. En utilisant des techniques de subduction, chacune des particules peut Ctre dCfinie a l'aide de vecteurs complets et orthonormaux et les probabilitks d'excitation sont directement relikes au recouvrement de ces vecteurs de base au moment de la coincidence de l'espace et du temps. Le modkle obCit pleinement aux exigences de la loi des 3n -6 degrks de libertC et on trouve qu'il exprime le mouvement des atomes en fonction de leur recouvrement avec les champs multipolaires disponibles du photon. En premiere approximation, on considkre l'interaction photon-molCcule comme le potentiel de Coulomb entre les champs Clectriques du photon et ceux des noyaux atomiques blindCs. On ne tient pas compte de la faible densit6 des Clectrons de valence, mais celle-ci devient importante au deuxikme ordre. Sur la base de cette hypothkse, ( a ) on peut ktablir une corrklation entre le mouvement molCculaire de translation et le champ dipolaire du photon et tpuiser ce dernier; ( b ) la rotation correspond a trois des cinq composantes du quadrupole du photon et ( c ) les modes internes d'ungerade sont permis en premier par un recouvrement avec l'octupole du photon. On discute de quelques conskquences de cette rtgle de l'octupole en se rtftrant particulikrement aux molCcules octakdriques 2 par...

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Vibration Spectra and Symmetry of Crystals

Cited by 49 publications

References 0 publications

Optical spectroscopic characterizations of laser irradiated olivine grains

Optical spectroscopic characterizations of laser irradiated olivine grains

Pressure-induced Phase Transitions in Defect Pyrochlores

A vectorial model of photon–molecule interactions and the development of an Octupole Rule of vibrational excitation

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