摘要:

AbstractInvestigation of the Raman spectra of the molten MgCl2‐KCl system by the use of factor analysis indicates that the melt is a two‐component system involving equilibrium between MgCl 42−and Mg2Cl 73−. The pure Raman spectra corresponding to these two species are recovered from the broad features via a self‐mo

ISSN:0377-0486    

DOI:10.1002/jrs.1250261002

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman (3100‐10 cm−1) and infrared (3100‐400 cm−1) spectra oftrans‐2‐methyl‐2‐butenenitrile [trans‐CH3CH =C(CH3)CN] were recorded for the gas, liquid and solid phases. Additionally, the far‐infrared (370‐60 cm−1) spectrum of the gas was recorded. These data were interpreted on the basis that only thetrans(two methyl groupstransto each other) isomer is present on purification. Only one of the methyl torsional fundamentals was observed and it corresponds to the methyl group on the same carbon atom as the cyano group. The experimental barrier to internal rotation is 610 ± 30 cm−1(1.74 ± 0.09 kcal mol−1). The structure, infrared intensities, Raman activities, depolarization ratios and vibrational wavenumbers were determined fromab initiocalculations using the RHF/3‐21G, RHF/6‐31G* and MP2/6‐31G* basis sets. These results are compared with those

ISSN:0377-0486    

DOI:10.1002/jrs.1250261003

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman spectra (3200‐20 cm−1) of the liquid and solid phases of 1‐bromo‐2‐methylpropene [BrHC=C(CH3)2] and the infrared (3200‐30 cm−1) spectra of the gas and solid were recorded. Additionally, qualitative depolarization values were obtained from the Raman spectrum of the liquid. All of the normal modes were assigned based on band contours, depolarization values, relative intensities and normal coordinate analysis. The torsional transition for the methyl grouptransto the bromine atom was observed in the far‐infrared spectrum of the vapor at 167 cm−1, and from this wavenumber the barrier to internal rotation was calculated to be 641 cm−1(1.83 kcal mol−1). Optimized structural parameters, barriers to internal rotation and the wavenumbers for the vibrational fundamentals were calculated using the RHF/STO‐3G*, RHF/LANL‐1DZ and/or MP2/LANL‐1DZ basis sets. All of the results are discussed and compared with the corresponding values obtained

ISSN:0377-0486    

DOI:10.1002/jrs.1250261004

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe relative SERS enhancement factors for pyridine adsorbed on a silver electrode were determined as a function of the laser wavelength and applied potential. The charge‐transfer (CT) contribution to the SERS intensity (I),Gct, was estimated from the excitation profiles(I vs. hv)and compared with theGctvalues previously obtained from theI vs.electrode potential curves. A critical discussion of the determination ofGctwith the aid of both methods is give

ISSN:0377-0486    

DOI:10.1002/jrs.1250261005

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe observation of surface‐enhanced Raman scatterings (SERS) from CO2molecules dissolved in aqueous solutions of silver and gold colloids measured with 850 nm near‐IR excitation is reported. Different types of surface enhancement and surface‐enhanced Raman spectra were observed. The SERS spectrum of CO2on colloidal gold is in good agreement with the spectrum of CO2dissolved in water. Two different types of SERS spectra were found for CO2on colloidal silver. They can be assigned to physisorbed and/or weakly chemisorbed CO2molecules and to strongly bonded CO2‐ negatively charged surface radicals, respectively. The enhancement factor for the stretching mode of carbon dioxide is estimated to be of the order of 102−104, depending on the kinds of metal and types of adsorption, which demonstrates that SERS on colloidal silver or gold particles in solution offers possibilities for detecting CO2dissolved in liquids at low conce

ISSN:0377-0486    

DOI:10.1002/jrs.1250261006

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractHigh‐pressure Raman spectra of liquid and solid CH4and CD4were measured up to 18 and 13 GPa, respectively, at 300 K in a gasketed diamond‐anvil cell. On the basis of visual observations under the polarizing microscope and changes in the Raman spectra, it was confirmed that there are only two solid phases (I and VII) for CH4and CD4at 300 K up to 18 GPa; no solid‐solid phase transition was found around 12 GPa, in contrast to earlier claims. In phase VII, some molecules are orientationally ordered, whereas others are orientationally disordered, just like the low‐temperature solid phases II, III, I

ISSN:0377-0486    

DOI:10.1002/jrs.1250261007

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe resonance Raman spectra of the adducts of cytochromecperoxidase with four cyanide isotopomers (12C14N−,13C14N−,12C15N−and13C15N−) are presented. The spectra reveal the presence of two conformers, an essentially linear conformer whosev(Fe—C) and δ(FeCN) modes occur at 445 cm−1and 407 cm−1, respectively (at pH 10) and a bent conformer which exhibits two modes at 355 cm−1and 445 cm−1(at pH 10). At pH values below 7, the linear formv(Fe—C) shifts to ∼455 cm−1in response to protonation of the distal histidyl imidazole (which strengthens the Fe—C bond). The stretching mode of the bent form experiences only a slight shift. This smaller shift of the bent form is consistent with the proposal that the bent form originates as a consequence of hydrogen bond formation with the off‐axis proton donor group of arginine (which is protonated at both pH values). The overall spectral response to pH changes reflects interactions with the bound ligand which may be important f

ISSN:0377-0486    

DOI:10.1002/jrs.1250261008

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman spectra of LiTa0.9Nb0.1O3single crystal were studied as a function of temperature between 300 and 1000 K. When heated above 900 K, the crystals transform from the ferroelectric phase to the paraelectric phase, and the Raman data suggest that the phase transition is second order. The softening of anA1mode was observed, but the ‘soft mode’ hardened at 120 cm−1. The mechanism of the phase transition is likely to be of the order‐disord

ISSN:0377-0486    

DOI:10.1002/jrs.1250261009

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250261001

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY