Raman Spectrum of TlCl0.6Br0.4 near Resonance

1973 ◽  
Vol 51 (15) ◽  
pp. 1657-1663 ◽  
Author(s):  
N. Krishnamurthy ◽  
B. H. Torrie
Keyword(s):  
Raman Spectrum ◽  
Raman Scattering ◽  
Single Crystals ◽  
Mixed Crystal ◽  
Resonant Scattering ◽  
Excitation Wavelength ◽  
Scattering Mechanism ◽  
Near Resonance ◽  
Exciting Wavelength ◽  
Densities Of States

Raman scattering from single crystals of TlCl0.6Br0.4 has been observed both as a function of temperature and excitation wavelength. The spectra exhibit strong one-phonon Raman scattering at 17 and 37 cm−1 and a weak two-phonon band centered at 296 cm−1, close to twice the LO frequency (q = 0) of the mixed crystal. From the temperature dependence and the calculated one- and two-phonon densities of states, it is shown that the 37 cm−1 line and the tail following it are an admixture of first- and second-order Raman scattering. The enhancement of the intensity of the 296 cm−1 band when the exciting wavelength is decreased from 5145 Å to 4545 Å is attributed to the resonant-scattering mechanism proposed by Fontana and Mulazzi.

Raman Scattering Study of Coalesced Single Walled Carbon Nanotubes

1998 ◽  
Vol 13 (9) ◽  
pp. 2405-2411 ◽  
Author(s):  
S. L. Fang ◽  
A. M. Rao ◽  
P. C. Eklund ◽  
P. Nikolaev ◽  
A. G. Rinzler ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Resonant Scattering ◽  
Radial Breathing Mode ◽  
Excitation Wavelength ◽  
Scattering Intensity ◽  
High Temperature Heat Treatment ◽  
Treated Sample ◽  
Scattering Study ◽  
Walled Carbon Nanotubes ◽  
Temperature Heat Treatment

High temperature heat treatment of single wall carbon nanotube bundles in flowing H2 was used to produce a significant fraction (∼40%) of diameter-doubled, or coalesced tubes with a mean diameter corresponding to that of ∼(20, 20) tubes. At three laser excitation wavelengths (514.5, 647, and 1064 nm), a reduction in the Raman scattering intensity of the strong radial and tangential modes was observed in the H2-treated sample, consistent with the reduced fraction of tubes in the sample after coalescence. However, using 488 nm excitation, little or no change is observed in the Raman spectrum after the H2 treatment, suggesting that this excitation wavelength couples only to chiral symmetry tubes. Using the 647 nm excitation, the effect of H2 treatment on the tangential band is quite unique, and a significant change in the shape of the tangential band was observed. Our lineshape analysis, and other results reported in this issue, suggest that this unique change of shape is due to lost scattering intensity from metallic tubes partially compensated by tangential mode scattering from the coalesced tubes. The normally prominent radial breathing mode band, which would be expected at ∼90 cm−1 for ∼(20, 20) tubes was not observed, indicating that these larger diameter tubes do not exhibit strong resonant scattering, at least at any of the wavelengths used in this study.

scholarly journals Raman scattering and luminescence in single crystals of the amino acid glycine C2H5NO2 with an admixture of croconic acid C5H2O5

2021 ◽  
Vol 2103 (1) ◽  
pp. 012070
Author(s):  
E V Balashova ◽  
A N Smirnov ◽  
Yu V Davydov ◽  
B B Krichevtsov ◽  
A N Starukhin
Keyword(s):  
Amino Acid ◽  
Raman Scattering ◽  
Single Crystals ◽  
Thin Plates ◽  
Excitation Wavelength ◽  
Scattering Spectra ◽  
Polarized Raman ◽  
Raman Scattering Spectra ◽  
532 Nm ◽  
Amino Acid Glycine

Abstract Single crystals of the amino acid glycine (Gly) C2H5NO2 doped with croconic acid (CA) C5H2O5 were synthesized by evaporation from an aqueous solution. The crystals grow in the form of hexagonal pyramids or thin plates. Analysis of polarized Raman scattering spectra (excitation wavelength of 532 nm) measured at room temperatures showed that crystals in the form of pyramids corresponded to γ-polymorph (γ-Gly), and crystals in the form of plates to α-polymorph of glycine (α - Gly). The presence of croconic acid molecules in the crystals is confirmed by the change in their color from white in pure Gly crystals to light or dark yellow, characteristic of CA crystals, as well as the presence of weak lines corresponding to CA in the Raman spectra. In single crystals of both Gly:CA polymorphs, strong green luminescence significantly exceeding the intensity of Raman scattering is observed in the range 400 - 700 nm with a maximum at 510 nm (2.44 eV) upon excitation at λ= 325 nm.

Raman scattering from impurities in nonmetals. II. Anharmonic effects

1979 ◽  
Vol 57 (1) ◽  
pp. 11-22
Author(s):  
H. C. Chow
Keyword(s):  
Raman Spectrum ◽  
Raman Scattering ◽  
Raman Line ◽  
Life Time ◽  
Resonant Scattering ◽  
Time Effect ◽  
Dipole Radiation ◽  
Anharmonic Effects ◽  
Spectrum Function

Anharmonic effects on the impurity Raman spectrum are examined on the basis of an approximately derived, nonphenomenological Raman spectrum function. It is shown that owing to the phonon life-time effect, anharmonicity broadens the zero-phonon Raman line and the accompanied satellite phonon Raman lines. The case of resonant scattering is re-examined and the result suggests that the dipole radiation formulation of Raman scattering, which is the basis of the present and some other treatments, is unsuited for demonstrating hot luminescence.

EFFECT OF EXCITATION WAVELENGTH ON THE RAMAN SPECTRUM OF HEXAGONAL DEFECTS IN 4H-SiC

2013 ◽  
Vol 27 (05) ◽  
pp. 1350035 ◽  
Author(s):  
RU HAN ◽  
XIAOYA FAN
Keyword(s):  
Raman Spectrum ◽  
Raman Scattering ◽  
Experimental Error ◽  
Wavelength Dependence ◽  
Excitation Wavelength ◽  
Structure Defects ◽  
Defect Zone ◽  
Electronic Raman Scattering ◽  
Optical Modes ◽  
Excitation Wavelength Dependence

The Raman spectra of 4H- SiC with hexagonal defect have been investigated as a function of the excitation wavelength. As the excitation wavelength increases, the excitation wavelength dependence of Raman spectrum of hexagonal defect is very different from that of the free defect zone in 4H- SiC . Four electronic Raman scattering peaks are seen to be significantly enhanced with longer wavelength excitation. In hexagonal defect, the optical modes ( E 2( TO ), E 1( TO ) and A 1( LO )) and the second-order Raman spectrum are broadened and redshifted as the excitation wavelength increased. But the positions of these bands obtained from the free defect zone do not change within our experimental error. Structure defects are regarded as the origin of those abnormal phenomena in hexagonal defect, and the structure ordering of hexagonal defect may have some similarity with SiC monofilaments.

Calcium Carbodiimide Compounds Revisited – Syntheses, Single Crystal Structure Determination and Vibrational Spectra of Ca11N6[CN2]2, Ca4N2[CN2] and Ca[CN2]

2008 ◽  
Vol 63 (5) ◽  
pp. 530-536 ◽  
Author(s):  
Olaf Reckeweg ◽  
Francis J. DiSalvo
Keyword(s):  
Crystal Structure ◽  
Raman Spectrum ◽  
Single Crystal ◽  
Single Crystals ◽  
Vibrational Spectra ◽  
Structure Determination ◽  
X Ray ◽  
Characteristic Features ◽  
Reported Data ◽  
Correct Data

Single crystals of Ca11N6[CN2]2 (dark red needles, tetragonal, P42/mnm (no. 136), a = 1456.22(5), and c = 361.86(2) pm, Z = 2), Ca4N2[CN2] (transparent yellow needles, orthorhombic, Pnma (no. 62), a = 1146.51(11), b = 358.33(4), and c = 1385.77(13) pm, Z = 4) and Ca[CN2] (transparent, colorless, triangular plates, rhombohedral, R3̅m (no. 166), a = 369.00(3), and c = 1477.5(3) pm, Z = 3) were obtained by the reaction of Na2[CN2], CaCl2 and Ca3N2 (if demanded by stoichiometry) in arc-welded Ta ampoules at temperatures between 1200 - 1400 K. Their crystal structures were re-determined by means of single crystal X-ray structure analyses. Additionally, the Raman spectra were recorded on these same single crystals, whereas the IR spectra were obtained with the KBr pellet technique. The title compounds exhibit characteristic features for carbodiimide units with D∞h symmetry (d(C-N) = 121.7 - 123.8 pm and ∡ (N-C-N) = 180°). The vibrational frequencies of these units are in the expected range (Ca11N6[CN2]2: νs = 1230, νs = 2008; δ = 673/645/624 cm−1; Ca4N2[CN2]: νs = 1230, νs = 1986; δ = 672/647 cm−1; Ca[CN2]: νs = 1274, νs = 2031, δ = 668 cm−1). The structural results are more precise than the previously reported data, and with the newly attained Raman spectrum of Ca11N6[CN2]2 we correct data reported earlier.

scholarly journals Raman scattering in YBa2Cu3O7 single crystals: Anisotropy in normal and superconductivity states

1998 ◽  
Vol 40 (3) ◽  
pp. 367-376 ◽  
Author(s):  
M. F. Limonov ◽  
A. I. Rykov ◽  
S. Tajima ◽  
A. Yamanaka
Keyword(s):  
Raman Scattering ◽  
Single Crystals

scholarly journals RESONANT RAMAN SCATTERING OF QUANTUM WIRE IN STRONG MAGNETIC FIELD

1999 ◽  
Vol 13 (17) ◽  
pp. 2275-2283 ◽  
Author(s):  
HYUN C. LEE
Keyword(s):  
Magnetic Field ◽  
Raman Scattering ◽  
Strong Magnetic Field ◽  
Coulomb Interaction ◽  
Quantum Wire ◽  
Spin Excitation ◽  
Momentum Dependence ◽  
Near Resonance ◽  
Resonant Raman ◽  
Resonant Raman Scattering

The resonant Raman scattering of a quantum wire in a strong magnetic field is studied, focused on the effect of long range Coulomb interaction and the spin–charge separation. The energy–momentum dispersions of charge and spin excitation obtained from Raman cross-section show the characteristc cross-over behaviour induced by inter-edge Coulomb interaction. The "SPE" peak near resonance in polarized spectra becomes broad due to the momentum dependence of charge velocity. The broad peak in the depolarized spectra is shown to originate from the disparity between charge and spin excitation velocity.

Solved and unsolved problems in the Raman spectrum of S 2− in KI single crystals

1978 ◽  
Vol 7 (1) ◽  
pp. 22-25 ◽  
Author(s):  
W. Holzer ◽  
S. Racine ◽  
J. Cipriani
Keyword(s):  
Raman Spectrum ◽  
Single Crystals
Sign in / Sign up

Export Citation Format

Share Document