Resonance enhancement of the non-totally symmetric vibrations in the raman spectra of para-benzosemiquinone radical anion

1989 ◽  
Vol 156 (1) ◽  
pp. 51-54 ◽  
Author(s):  
G.N.R. Tripathi ◽  
Q. Sun ◽  
R.H. Schuler
Keyword(s):  
Raman Spectra ◽  
Radical Anion ◽  
Resonance Enhancement

Resonance Raman spectra of the TCNE radical anion dimer in ethanol

1982 ◽  
Vol 91 (4) ◽  
pp. 296-298 ◽  
Author(s):  
Susumu Matsuzaki ◽  
Tetsuya Mitsuishi ◽  
Koichi Toyoda
Keyword(s):  
Raman Spectra ◽  
Radical Anion ◽  
Resonance Raman ◽  
Resonance Raman Spectra

UV Resonance Raman Spectra of Bacillus Spores

1992 ◽  
Vol 46 (2) ◽  
pp. 357-364 ◽  
Author(s):  
E. Ghiamati ◽  
R. Manoharan ◽  
W. H. Nelson ◽  
J. F. Sperry
Keyword(s):  
Aqueous Solutions ◽  
Bacillus Cereus ◽  
Raman Spectra ◽  
Dipicolinic Acid ◽  
Resonance Raman ◽  
Vegetative Cells ◽  
Resonance Enhancement ◽  
Uv Resonance Raman ◽  
Bacillus Spores ◽  
Resonance Raman Spectra

UV resonance Raman spectra of Bacillus cereus, Bacillus megaterium, and Bacillus subtilis endospores have been excited at 222.7,230.7,242.5, and 251.1 nm, and spectra have been compared with those of vegetative cells. The resonance Raman spectra of aqueous solutions of dipicolinic acid and calcium dipicolinate have been measured at the same wavelengths. Spectra of endospores and their corresponding germinated spores show only modest differences when excited at 222, 231, and 251 nm. However, very substantial differences appear when excitation occurs at 242 nm. Difference spectra obtained at 242 nm by subtracting spectra of germinated spores of Bacillus cereus from spectra of their corresponding endospores are attributed almost entirely to dipicolinate. Vegetative cells and endospores show large spectral dissimilarities at all exciting wavelengths. These spectral differences, which vary strongly with exciting wavelength, appear to be the result of large differences in the amounts and composition of proteins and nucleic acids, especially ribosomal RNA. The very substantial resonance enhancement of Raman spectra has been obtained from aqueous solutions of pure dipicolinic acid and of sodium and calcium dipicolinate salts, as well as spores at the various exciting wavelengths. The strong enhancement of dipicolinate spectra in spores, however, was noted only with 242-nm excitation. Consequently, only with 242-nm light was it possible to selectively and sensitively excite and study calcium dipicolinate in spores. Resonance enhancement of the dipicolinate spectra with 242-nm excitation appears due primarily to resonance interactions with n-π* electronic transitions associated with the pyridine ring and/or the carboxylate group.

scholarly journals Transient Raman spectra, structure, and thermochemistry of the thiocyanate dimer radical anion in water

2017 ◽  
Vol 146 (21) ◽  
pp. 214305 ◽  
Author(s):  
Ireneusz Janik ◽  
Ian Carmichael ◽  
G. N. R. Tripathi
Keyword(s):  
Raman Spectra ◽  
Radical Anion

scholarly journals Properties of a new one-dimensional semiconducting ternary compound: TEDA (triethylenediamine)•I2.5•TCNQ

1989 ◽  
Vol 67 (4) ◽  
pp. 619-624 ◽  
Author(s):  
André D. Bandrauk ◽  
K. D. Truong ◽  
C. Carlone
Keyword(s):  
Raman Spectra ◽  
Ternary Compound ◽  
Resonance Raman ◽  
Resonance Excitation ◽  
Temperature Phase ◽  
Linear Chains ◽  
Resonance Enhancement ◽  
Resonance Raman Spectra ◽  
Doubly Charged ◽  
Low Temperature Phase

A new semiconducting ternary compound of stoichiometry TEDA•I2.5•TCNQ is reported. The crystal is made up of linear chains of TCNQ−1/2, nonlinear chains of I3−, and monodides of doubly charged triethylenediamines (TEDA). Half the TEDA's are hydrogen bonded to the TCNQ's and I3−. The conductivity measurements indicate semiconducting behaviour with two discontinuities in activation energy, one at high (330 K) and the other at low (160 K) temperatures. Resonance Raman spectra of the crystals manifest strong resonance enhancement of the iodide moieties. In particular, selective resonance excitation at 647 nm of nonsymmetric I3− is observed, thus indicating an increasing asymmetry of the I3− in the low temperature phase and suggesting coupling between the three species in this phase. Keywords: semiconductor, ternary compound, resonance Raman spectra, tetracyanoquinodimethane (TCNQ), tri-iodide (I3).

scholarly journals Resonance-Enhanced Raman Spectroscopy on Explosives Vapor at Standoff Distances

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Anneli Ehlerding ◽  
Ida Johansson ◽  
Sara Wallin ◽  
Henric Östmark
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectra ◽  
Wavelength Range ◽  
Vapor Phase ◽  
Cross Sections ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Resonance Enhancement ◽  
Enhancement Factors ◽  
532 Nm

Resonance-enhanced Raman spectroscopy has been used to perform standoff measurements on nitromethane (NM), 2,4-DNT, and 2,4,6-TNT in vapor phase. The Raman cross sections for NM, DNT, and TNT in vapor phase have been measured in the wavelength range 210–300 nm under laboratory conditions, in order to estimate how large resonance enhancement factors can be achieved for these explosives. The results show that the signal is enhanced up to 250,000 times for 2,4-DNT and up to 60,000 times for 2,4,6-TNT compared to the nonresonant signal at 532 nm. Realistic outdoor measurements on NM in vapor phase at 13 m distance were also performed, which indicate a potential for resonance Raman spectroscopy as a standoff technique for detection of vapor phase explosives. In addition, the Raman spectra of acetone, ethanol, and methanol were measured at the same wavelengths, and their influence on the spectrum from NM was investigated.

scholarly journals Raman spectroelectrochemical study of redox dye Nile blue adsorbed or electropolymerised at a gold electrode

Chemija ◽  
2019 ◽  
Vol 30 (2) ◽  
Author(s):  
Regina Mažeikienė ◽  
Gediminas Niaura ◽  
Olegas Eicher-Lorka ◽  
Albertas Malinauskas
Keyword(s):  
Raman Spectra ◽  
Electrode Potential ◽  
Gold Electrode ◽  
Nile Blue ◽  
Visible Spectrum ◽  
Modified Electrodes ◽  
Solution Ph ◽  
Continuous Growth ◽  
Resonance Enhancement ◽  
Light Absorbance

The redox dye Nile blue has been adsorbed and electrochemically polymerised at a roughened gold electrode. The resulting modified electrodes were subjected to Raman spectroelectrochemical study with 785 nm laser line excitation. For both types of electrodes, well-expressed and rich in features Raman spectra were obtained. The spectra are closely related to those of another oxazine type redox dye Meldola blue. At solution pH 7.0, the overall intensity of the Raman spectra for both types of modified electrodes appears higher than in a pH 1.0 solution. Probably, this is caused by different light absorbance properties of this dye in two solutions. In a pH-neutral solution, the dye possess light absorbance in the red range of the visible spectrum, thus, resonance enhancement is possible. The intensity of the Raman spectra also increases by the shift of the electrode potential to higher positive values. This effect could be understood taking into account an intensifying colouration of the dye at a stepwise increase of the electrode potential due to a continuous growth of the content of oxidised forms within the electrode-bound layer.

Optical and Raman spectra of single crystals of perylene-TCNQ charge transfer complexes

1982 ◽  
Vol 60 (5) ◽  
pp. 588-595 ◽  
Author(s):  
A. D. Bandrauk ◽  
K. D. Truong ◽  
C. Carlone
Keyword(s):  
Raman Spectrum ◽  
Charge Transfer ◽  
Single Crystals ◽  
Raman Spectra ◽  
Optical Transmission ◽  
Charge Transfer Complexes ◽  
One Dimensional ◽  
Resonance Enhancement ◽  
First Time ◽  
Transmission And Reflection

Optical transmission and reflection measurements are reported for the quasi one dimensional solids perylene-TCNQ (P1T1) and (perylene)3-TCNQ (P3T1) in the region from 300 to 1200 nm. Raman spectra of single crystals of both compounds were obtained from 20 to 3000 cm−1. With 457.9 nm excitation, combinations and overtones of perylene are observed for the first time. A complete Raman spectrum of perylene and its deuterated homologue including librations is thus obtained via selective resonance enhancement of that molecule.

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