Zwei-Phononen-Absorptionsspektren und Dispersion der Schwingungszweige in Kristallen der Kalkspatstruktur

Abstract

Polarized reflection spectra between 4.000 and 20 cm -1 and absorption spectra (at temperatures of liquid helium) between 2.000 and 650 cm -1 have been measured of the isomorphous crystals NaNO3, CaCOa, MgCO 3 (D~a) and of CaMg (CO3) 2 (C32i). The wavenumbers of the fundamental infrared transitions and of the twophonon-combinations have been determined. The combinationbands show a structure, which allows some insight into the wavevector dispersion of the phonon branches of these crystals. Selection rules have been worked out for several points in the interior and on the border of the Brillouin zone. By comparison with the spectra they give evidence for the presence of critical points of the phonon-branches for wavevectors parallel to the trigonal axis of the crystal.

The mineral composition and spatial distribution of the dust ejecta of NGC 6302

“…The spectral behaviour of carbonates has been measured several times in previous studies (e.g. Hellwege et al 1970;Penman 1976;Orofino et al 1997;Yamagishi et al 2001). The measured mid-infrared bands arise mainly from the carbonate anion.…”

“…The 7 µm band can be attributed to the C = O stretching mode whereas the 11 and 14 µm bands are caused by the out-of-plane and in-plane bending modes. The low frequency bands beyond 25 µm are due to translation of the metal cations and represent motions perpendicular and parallel to the plane of the carbonate anions (Hellwege et al 1970). …”

Hyper‐Raman Scattering from Infrared Active Modes in Calcite Crystals

“…1. These phonons are not Raman active, but are well-known from infrared data [12]. The frequencies of these phonons are marked by arrows in Fig.…”

Lattice-Dynamical Estimation of Atomic Displacement Parameters in Carbonates: Calcite and Aragonite CaCO3, Dolomite CaMg(CO3)2 and Magnesite MgCO3

“…calcite, magnesite, dolomite and aragonite) plus those of quartz, a few silicates such as some members of the olivine group (forsterite Mg 2 SiO 4 and monticellite CaMgSiO 4 ), andalusite Al 2 SiO 5 , diopside CaMgSi 2 O 6 and some oxides containing Al or Be, such as corundum, chrysoberyl and bromellite. Most of these data are Raman-and IR-active frequencies obtained by different authors (Hellwege et al, 1970;Cowley & Pant, 1973;Frech et al, 1980; for additional details, and reference to the sources for data on noncarbonates, see Pilati, Demartin, Cariati et al, 1993, Pilati et al, 1990c, 1994, 1995. The lowest branches of the phonon dispersion curves were included when available, as for calcite, quartz, forsterite and andalusite.…”

“…Hence, the force ®eld reported in Table 1 has been derived by considering all these substances simultaneously and changing all the parameters. The calculated Raman-and IR-active frequencies are reported in Table 2, together with the corresponding experimental values obtained by Hellwege et al (1970) or Frech et al (1980); the corresponding values for the lowest phonon dispersion curves of calcite along [001] are reported in Table 3. The agreement is very good.…”