摘要:

AbstractThe vibrational spectrum of ammonium acetate at room temperature and 77 K is reported. The observed factor group splitting between four acetate ions is slight in each internal mode. The normal coordinate analysis is carried out under the assumption of neglect of hydrogen atoms. Good agreement between observed and calculated frequencies is obtained for the lattice vibrations. It is clarified that the hydrogen bond has considerable strength and a very strong Raman band at 58 cm−1in CH3CO2NH4is a libration of the acetate ion about an axis perpendicular to the molecular plane. The strong IR band at 260 cm−1in CH3CO2NH4is discus

ISSN:0377-0486    

DOI:10.1002/jrs.1250160502

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractRaman spectra of Mg(ClO4)2·6H2O single crystal in different polarizations in the temperature range 350–110 K are presented. Three phase transitions were found at 325, 272 and 225 K. The transition at 272 K is associated with the rotation of crystallographicaandbaxes with respect to the space‐fixed coordinate axesXandYin theabplane. The transition at 325 K occurs as a result of reorientation of the ClO4−ion and that at 225 K as a result of the tumbling motion of the aquo c

ISSN:0377-0486    

DOI:10.1002/jrs.1250160503

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractIn the treatment of absorption spectra and Raman excitation profiles of polyatomic molecules, relaxation constants appear as ‘soft’ parameters. It is shown that the spectra of non‐linear Raman scattering under resonance pumping conditions are sensitive to variations in the relaxation constants and the number of active vibrations, especially when ‘extra’ resonances are included. This is demonstrated by calculations of coherent Stokes Raman scattering spectra carried out using the density of states model and displaced independent harmonic oscillators. The use of non‐linear Raman spectra for checking the reliability of the model descriptions ofS0–S1transition

ISSN:0377-0486    

DOI:10.1002/jrs.1250160504

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe influence of cations on aluminosilicate zeolite formation is well recognized. This Raman study showed that on a molecular level, there is a significant difference in the type of silicate species that are solubilized by tetramethylammonium hydroxide and sodium hydroxide at certain hydroxide ion concentrations. A cubic, cage‐like silicate species is formed in 1.0–1.4Mtetramethylammonium hydroxide, whereas no such species was formed in alkali metal hydroxide at any concentration. Band assignments for the cubic species [(CH3)4N]8Si8O20are made from the Raman and infrared spectroscopic data. Elucidation of such structural effects by Raman spectroscopy can help explain the unique influence of the cation on zeolite format

ISSN:0377-0486    

DOI:10.1002/jrs.1250160505

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractUsing a model calculation of the unperturbed two‐phonon density of states for the frequency region encompassing the 2ν4overtone of NH4Cl, together with the quantum field Green function approach of Ruvalds and Zawadowski, both the shape of the perturbed two‐phonon band in the Raman spectra and the detalled spectral evolution of the polariton spectra in this frequency regime as a function of wave vectorqhave been calculated. The calculation, which does not require a two‐phonon bound state, is in good agreement with expe

ISSN:0377-0486    

DOI:10.1002/jrs.1250160506

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe resonance Raman spectra of a series of cyanine dyes, with various lengths of the methine chain, have been obtained. This series consists of the 1,1′‐diethyl‐2,2′‐quino group basic structure. Raman spectra of some dyes with closely related structures were also measured. The Raman bands are assigned to normal modes arising from particular molecular moieties. For comparison purposes, the IR spectra of these dyes are also

ISSN:0377-0486    

DOI:10.1002/jrs.1250160507

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractIn the presence of an external magnetic field, shallow acceptor levels in II‐VI semiconductors split into aJ=3/2 quartet of nearly evenly spaced levels. At cryogenic temperatures only theMJ= −3/2 state is thermally occupied, and two transitions are expected: ΔM= 1 (−3/2 to −1/2) with αxxand αxypolarizabilities (z is the direction of applied field) and ΔM=2 (−3/2 to +1/2) with αxzand αyzpolarizabilities. In addition to those transitions we have observed at high magnetic fields (H⩽4T) a third transition with αxxand αxypolarizability; we assign it as ΔM= 3 and show that although it is strictly forbidden in zero field, its cross‐section varies theoretically asH2, and experimentally it becomes comparable in intensity to the ΔM= 2 transition in both ZnTe: Li and ZnTe: Ag at 10 T. This analysis allows a more accurate evaluation of the gyromagnetic ratiog= − 2k=0.567 ± 0.025 and of the crystal field parameter q̃ in the spin Hamiltonian of Zn Te: Li as q̃ = −0.012±0.006; the sign and magnitude of q̃ have previously been in doubt and can be different for different acceptors. Non‐zero spin‐flip energies are found, interpreted as due to strain or exchange. These appear to vary with acceptor concentration, and areE1/2= 1.45± 0.29 cm−1andE3/2=4.39±0.14 cm−1for 0.01% Li. The fact thatE3/2≈︁ 3E1/2indicates that the mean field approximation is valid, with an effective fiel

ISSN:0377-0486    

DOI:10.1002/jrs.1250160508

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe temperature dependence of the Raman spectrum of the plastic solid carboranep‐C2B8H10was studied in the range 15–470 K. Unlike the icosahedral carboranes C2B10H12, this ‘stretched’ carborane has only one plastic phase, probably with anisotropic reorientations. A phase transition to an ordered crystal takes place at 188 K. In a sealed capillary the substance melts at 433 K. The Raman spectrum ofp‐C2B8H10, originally having no background, acquired the background after the sample had been repeatedly heated and cooled. It was found that the background intensity depends on the thermal prehistory of the sample; it slowly diminishes on heating, and several degrees below the melting point the background disappears completely and re‐emerges in the spectrum

ISSN:0377-0486    

DOI:10.1002/jrs.1250160509

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe Raman spectra of pure silica core fibres revealed the presence of molecular oxygen, which may be responsible for two absorption bands, one at 0.76 and the other at 1.27 μm

ISSN:0377-0486    

DOI:10.1002/jrs.1250160510

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractRaman microprobe spectra were obtained from tetramethoxymethane tetranitrate, 1,3,5‐trinitro‐1,3,5‐triazacyc‐lohexane and 2,4,6‐trinitro‐l‐methylbenzene adsorbed on silica gel and supported on glass. The nitro compounds were detected at levels down to 1 μg on silica gel and 100 pg on glass and gave identifiable spectra. The results were compared with those obtained in earlier macro

ISSN:0377-0486    

DOI:10.1002/jrs.1250160511

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY