摘要:

AbstractRaman spectra of the liquid crystal PPU [p‐(p‐ethoxyphenylazo)‐phenyl undecylenate] have been measured as a function of temperature covering all phases. A pronounced hysteresis which involves a new state has been observed during the crystalline‐nematic transition. The Raman intensities in the nematic phase show a temperature dependence in the presence of an external magneti

ISSN:0377-0486    

DOI:10.1002/jrs.1250030202

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractResonance Raman spectra are reported for potassium manganate powder employing a number of exciting frequencies within the electronic absorption region of the material.In analyzing the observed variations in the relative intensities for resonance effects we have considered δM/δq(M= transition moment andq= normal coordinate) as the dominant term in the theoretical derivation of the expression for Raman intensity. This approach leads to excellent agreement between the experimental intensity data on both the fundamental as well as the first overtone of the symmetric stretching mode of the MnO 42−ion and the derived theoretical expres

ISSN:0377-0486    

DOI:10.1002/jrs.1250030203

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe Raman spectra of gaseous hydrazine and hydrazine‐d4have been recorded from 40 to 3500 cm−1. For the ‘light’ molecule, strongly polarized lines at 3398, 3329 and 1076 cm−1have been assigned to the NH antisymmetric stretch, NH symmetric stretch, and NN stretch, respectively. For the hydrazine‐d4molecule, strongly polarized lines at 2442, 2422, 1031, 930 and 749 cm−1have been assigned to the ND antisymmetric stretch, ND symmetric stretch, NN stretch, ND2was and ND2rock, respectively. The Raman spectra of both solid hydrazine and hydrazine‐d4have been recorded and the splitting in the intramolecular fundamental region indicates that there are at least four molecules per primitie cell. In the lattice region of the spectra the optical translations and librations are assigned and the number of lattice modes rules out both of the space groups previously proposed for hydrazine from sca

ISSN:0377-0486    

DOI:10.1002/jrs.1250030204

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe Raman spectra of (NH4)2SO4single crystals have been recorded and measured using an Ar+laser as a scource of excitation. The polarization behaviour of the Raman lines in different crystal orientations has been studied. The observed shifts in the range 15–3400 cm−1have been attributed to the phonons of different symmetry species originating from the internal modes of NH 4+and SO 42−ions and the lattice modes calculated from group theoretical consi

ISSN:0377-0486    

DOI:10.1002/jrs.1250030205

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe resonance Raman effect has been applied for the first time to the study of the structure of adsorbed molecules and the interaction between adsorbents and adsorbates. By rotating a sealed sample and using Ar+laser excitation, the resonance Raman spectrum of I2adsorbed on the silicas was measured for the second to the fifth harmonics. The peak frequencies were slightly shifted from those for the gas molecule, indicating the weak bondage between the surface OH groups and iodine molecules. When iodine monochloride was adsorbed on a silica surface, the resonance Raman spectrum of I2adsorbed on silicas was also observed.

ISSN:0377-0486    

DOI:10.1002/jrs.1250030206

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe Raman spectra of NH3SO3and ND3SO3single crystals at 300 and 30 K have been studied in the 4000 to 5 cm−1range. Infrared spectra of polycrystalline samples have been recorded for comparison in the 4000 to 60 cm−1region. Twenty‐three Raman and six infrared lattice modes from respectively twenty‐four and fifteen expected ones have been observed. An assignment in terms of factor group symmetry species, rotational and translational vibrations is given. Static and correlation field splitting of internal vibrations is discussed and an assignment of the bands to group frequencies and molecular and factor group symmetry species is proposed. Torsional vibrations are discussed with respect to the amplitude of this motion and the potential barrier opposed to the rotation of the NH3group has been determined. The NH stretching frequencies are correlated with the N…︁O distances and thevNH band breadth and structure ar

ISSN:0377-0486    

DOI:10.1002/jrs.1250030207

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe Raman spectra of single crystals of NaNH4SeO4·2H2O in various orientations are reported for the temperature range 293–89 K. NaNH4SeO4·2H2O undergoes a transition at 180 K from a paraelectric phase to a ferroelectric phase. The changes in the Raman spectra as the crystal is cooled support the evidence from magnetic resonance studies that the transition is of a displacive type with an associated overdamped soft mode. Ordering of the NH 4+ions but not of the complete crystal occurs at the transition temper

ISSN:0377-0486    

DOI:10.1002/jrs.1250030208

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe Raman spectra in the lattice region (0–400 cm−1) of single crystals of NaNH4SO4·2H2O in various orientations are reported for the temperature range 293–87 K. NaNH4SO4·2H2O undergoes a transition at 101 K from a paraelectric phase to a ferroelectric phase. The changes in the Raman spectra as the crystal is cooled support the evidence from magnetic resonance studies that a large lattice distortion occurs at the transition temp

ISSN:0377-0486    

DOI:10.1002/jrs.1250030209

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractA technique is described for the frequency calibration of high‐resolution Raman spectra recorded on photographic plates. The frequencies of the Th calibration spectrum are fitted to a calibration polynomial in the observed positions, and the coefficients of this polynomial are determined as functions of the grating angle. For a given calibration the polynomial coefficients are constrained to the values of these functions. In this way the information from all previous calibration spectra is used to improve the accuracy of the calibration of any single exposure. Further, a valuable check is obtained on the overall experimental procedure by requiring the polynomial coefficients to be smooth functions of the grating angl

ISSN:0377-0486    

DOI:10.1002/jrs.1250030210

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY

摘要:

AbstractThe Raman spectra in the region 400–4000 cm−1of single crystals of NaNH4SO4·2H2O in various orientations are reported for the temperature range 293–87K. NaNH4SO4·2H2O undergoes a transition at 101 K from a paraelectric phase to a ferroelectric phase. The changes in the Raman spectra of the constituent species, NH 4+, SO 42−and H2O as the temperature is lowered indicate that below the phase transition there are non‐equivalent ions in the unit cell. The abruptness of the spectral changes at 101 K suggests a large lattice distortion in accord with the predictions of magnetic re

ISSN:0377-0486    

DOI:10.1002/jrs.1250030211

出版商:John Wiley&Sons, Ltd.    

年代:1975

数据来源: WILEY