摘要:

AbstractLes spectres Raman et infrarouge des acides acétylènedicarboxylique H2C4O4D2C4O4et de leurs sels alcalins KHC4O4, KDC4O4et K2C4O4ont été enregistrés de 3000 à 200 cm−1. L'analyse du facteur de dépolarisation nous a permis de conclure que I'acide, le sel acide et le sel neutre sont de symétries respectivesC2h,CSetD2d. Une comparaison des conformations avec celles déterminées en série oxalique a été réalisée. Une attribution des vibrations fondamenta

ISSN:0377-0486    

DOI:10.1002/jrs.1250170502

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractSurface‐enhanced Raman scattering (SERS) of adenine, adenosine, 2′‐deoxyadenosine, 5′‐dAMP, 5′‐rAMP, 5′‐rADP and 5′‐rATP adsorbed on aqueous Ag sol has been investigated. A shift of the adenine ring breathing mode from 746 to 735 cm−1with increasing adenine concentration is interpreted as reflecting the reorientation of adenine on the Ag surface. Such a shift is not observed for adenosine, 2′‐deoxyadenosine and 5′‐dAMP. SERS spectra of 5′‐rAMP, 5′‐rADP and 5′‐rATP can be obtained either at neutral pH in the presence of pyridine or by lowering the pH of the Ag sol. The pH effect is discussed i

ISSN:0377-0486    

DOI:10.1002/jrs.1250170503

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractRaman spectra have been recorded for thecis‐transisomers of retinal homologues. They include the all‐trans, 9‐cis, 11‐cis, and 13‐cisisomers of retinylideneacetaldehyde (C22aldehyde), which have a longer polyene chain than retinal (C20aldeyhde), and the all‐trans, 7‐cisand9‐cisisomers of β‐ionylidenecrotonaldehyde (C17aldehyde) and β‐ionylideneacetaldehyde (C15aldehyde), which have a shorter chain. The homologues were prepared by the stepwise elongation of the conjugated chain. Thecisisomers were isolated by means of HPLC from a photoisomerization mixture of the all‐transisomer, and the configuration of each isomer was determined by1H NMR. The Raman spectra were recorded for flowing CCl4solutions under pre‐resonant conditions by using the 514.5 nm (C22aldehyde) or 457.9 nm (C17andC15aldehydes) line of an Ar+laser. Comparison of the spectra confirmed the key bands for the unmethylatedcisconfigurations (7‐ and 11‐cis), distinguishing them from the methylatedcisconfigurations (9‐ and 13‐cis), which were reported in a previous paper. It revealed also key bands for the all‐transparts of mono‐cisisomers, i.e. th

ISSN:0377-0486    

DOI:10.1002/jrs.1250170504

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractCompounds of general formula M I3[M′III(SO4)3] exhibit a columnar structure and, at room temperature, belong to theC 52h,C 23iandC 63vsymmetry space groups with, respectively, M1T1, M′III In; MIT1, M′IIIFe; and MICs, M′III Fe.The Raman spectra of powder samples have been recorded in the temperature range 77–600 K. These vibrational studies indicate the role played by the SO4groups and MIcations in the phase transitions. All the compounds follow a space group phase sequence in accordance with the general point gr

ISSN:0377-0486    

DOI:10.1002/jrs.1250170505

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractResonance Raman (RR) spectra obtained with several excitation wavelengths are compared for the following porphyrin‐IX compounds: free‐base protoporphyrin‐IX, meso‐porphyrin‐IX and haematoporphyrin‐IX and copper‐protoporphyrin‐IX and copper‐mesoporphyrin‐IX dimethyl esters. Certain bands in the RR spectra of all the free‐base porphyrins or copper complexes are unaffected with respect to frequency, whereas there is a shift in the frequencies of some vibrational modes in some systems. From a comparative study of the systems which have identical geometrical arrangements, no extra features were found in the RR spectra of protoporphyrin which can be attributed directly to the vinyl group modes. This suggests that the vibrational modes of vinyl groups do not distort the excited electronic state substantially, and are not effective in vibronic coupling with the electronic states of the porphyrin macrocycle and therefore do not gain intensity under resonance excitation. Most of the vibrational modes are strongly coupled and there are no extra distinct features in the RR spectra of PP which may be associated with selective vibrational coupling of the vinyl group modes with the por

ISSN:0377-0486    

DOI:10.1002/jrs.1250170506

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractA system consisting of a mode‐locked and cavity‐dumped picosecond laser and gated (5 ns) intensified diode array detector has been used to evaluate the potential of diode arrays as detectors in fluorescence rejection measurements of Raman spectra. Successful fluorescence rejection was observed, but both the level of rejection and the signal‐to‐noise improvement observed would be substantially improved if the operating characteristics of the laser system and of the array were different. It was demonstrated that the diode array opens several times, at intervals ofca15.5 ns, for each trigger pulse s

ISSN:0377-0486    

DOI:10.1002/jrs.1250170507

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractAn extension of the Fleming and Johnson procedure is presented for determining the molecular third‐order susceptibility parameters from three characteristic intensities within a CARS line profile (Imax,Imin,Imid). For CARS excitation close to a molecular one‐photon resonance, these three intensity values taken from one spectrum do not suffice for the determination of all relevant parameters. A simple procedure is given for overcoming this by combining the information from all the spectra within a concentration series, keeping the frequency of the CARS pump laser fixed. Uncertainty in the measuredImidvalue is overcome by applying a least‐squares fit of the spectra.Results obtained from resonance CARS measurements for Rhodamine 6G in ethanol are

ISSN:0377-0486    

DOI:10.1002/jrs.1250170508

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe pure rotation Raman spectrum of17O18O has been recorded photographically using laser excitation and a spectrograph with a reciprocal linear dispersion of 1.4 cm−1mm−1at 488.0 nm. The followingB0,D0andr0values were obtained;B0=1.31546±0.00002 cm−1, 106D0=3.50±0.05 cm−1andr0=121.072

ISSN:0377-0486    

DOI:10.1002/jrs.1250170509

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250170501

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY