Dependence of the Raman spectra of drug substances upon laser excitation wavelength

2006 ◽  
Vol 37 (1-3) ◽  
pp. 335-341 ◽  
Author(s):  
Fiona C. Thorley ◽  
Kurt J. Baldwin ◽  
David C. Lee ◽  
David N. Batchelder
Keyword(s):  
Raman Spectra ◽  
Laser Excitation ◽  
Excitation Wavelength ◽  
Drug Substances

Raman spectra of twisted bilayer graphene close to the magic angle

2D Materials ◽  
2022 ◽  
Author(s):  
Tiago Campolina Barbosa ◽  
Andreij C. Gadelha ◽  
Douglas A. A. Ohlberg ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Laser Excitation ◽  
Bilayer Graphene ◽  
Geometrical Model ◽  
Excitation Wavelength ◽  
Magic Angle ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Excitation Laser ◽  
Twisted Bilayer Graphene

Abstract In this work, we study the Raman spectra of twisted bilayer graphene samples as a function of their twist-angles (θ), ranging from 0.03º to 3.40º, where local θ are determined by analysis of their associated moiré superlattices, as imaged by scanning microwave impedance microscopy. Three standard excitation laser lines are used (457, 532, and 633 nm wavelengths), and the main Raman active graphene bands (G and 2D) are considered. Our results reveal that electron-phonon interaction influences the G band's linewidth close to the magic angle regardless of laser excitation wavelength. Also, the 2D band lineshape in the θ < 1º regime is dictated by crystal lattice and depends on both the Bernal (AB and BA) stacking bilayer graphene and strain soliton regions (SP) [1]. We propose a geometrical model to explain the 2D lineshape variations, and from it, we estimate the SP width when moving towards the magic angle.

Effects of laser excitation wavelength and optical mode on Raman spectra of human fresh colon, pancreas, and prostate tissues

2014 ◽  
Vol 45 (9) ◽  
pp. 773-780 ◽  
Author(s):  
Ran Li ◽  
Dominique Verreault ◽  
Andrea Payne ◽  
Charles L. Hitchcock ◽  
Stephen P. Povoski ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Laser Excitation ◽  
Excitation Wavelength ◽  
Optical Mode

Effects of Excitation Wavelength on the Raman Spectra of Vanadium(V) Oxo Compounds

1996 ◽  
Vol 100 (47) ◽  
pp. 18357-18362 ◽  
Author(s):  
Jan-Christoph Panitz ◽  
Alexander Wokaun
Keyword(s):  
Raman Spectra ◽  
Excitation Wavelength ◽  
Oxo Compounds

Intense Photoluminescence and Photoluminescence Enhancement of Silicon Nanocrystals by Ultraviolet Irradiation

2007 ◽  
Vol 31 ◽  
pp. 74-76 ◽  
Author(s):  
P.T. Huy ◽  
P.H. Duong
Keyword(s):  
Silicon Nanocrystals ◽  
Room Temperature ◽  
Laser Excitation ◽  
Uv Light ◽  
Irradiation Time ◽  
Excitation Wavelength ◽  
Nonradiative Recombination ◽  
Emission Yield ◽  
Recombination Centers ◽  
Pl Intensity

Photoluminescence (PL) from silicon nanocrystals deposited on top of silica-glass template and from silicon nanocrystals in nc_Si/SiO2 multilayer films were studied as a function of ultraviolet (UV) laser irradiation time in vacuum. Both the films exhibit intense visible PL at room temperature under laser excitation. It was found that upon prolong irradiation time using a He-Cd laser (325 nm) the PL intensity of the films was spectacularly enhanced. The process is reversible and does not happen with excitation wavelength longer than 400 nm. Upon introducing air into the measurement chamber, a rapid decrease of the PL intensity was recorded. This observation suggests that the UV light may lead to modification of nonradiative recombination centers in the films and thus improves the emission yield of silicon nanocrystals.

R-Line Luminescence from Trace Amounts of Cr3+ in Aluminum Oxide and its Dependence on Sample Hydration

2002 ◽  
Vol 56 (8) ◽  
pp. 1055-1058 ◽  
Author(s):  
Chen Zuo ◽  
Paul W. Jagodzinski
Keyword(s):  
Aluminum Oxide ◽  
Raman Spectra ◽  
Laser Excitation ◽  
Sample Surface ◽  
Optical Spectra ◽  
Water Molecules ◽  
Commercial Products ◽  
Degree Of Hydration ◽  
Setting Reaction ◽  
Octahedral Sites

The R-line luminescence is observed in the Raman spectra of α- and γ-Al2O3 with chromium concentrations of less than 1 ppm. The same signals were previously used to monitor the setting reaction of dental cements. With laser excitation <690 nm, the R-line luminescence can be observed in the optical spectra of most commercial products containing α-Al2O3. It is found that the intensities of R-line signals are related to the degree of hydration of the α-Al2O3 sample, which can be explained by the formation of additional octahedral sites for Cr3+ near the sample surface involving oxygen atoms from the Al2O3 matrix and from absorbed water molecules.

Raman Apparatus Using Laser Excitation and Polarization Measurements. Rotational Spectrum of Fluorine

1969 ◽  
Vol 23 (1) ◽  
pp. 8-12 ◽  
Author(s):  
Howard H. Claassen ◽  
Henry Selig ◽  
Jacob Shamir
Keyword(s):  
Laser Beam ◽  
Raman Spectra ◽  
Laser Excitation ◽  
Scattered Light ◽  
Rotational Constant ◽  
Emission Lines ◽  
Optical Systems ◽  
Rotational Spectrum ◽  
Polarization Measurements

Various schemes are compared for measuring depolarization factors in Raman spectra with laser excitation. Optical systems are discussed for producing a laser beam free of unwanted emission lines and for focusing scattered light on the slit and on the detector. The rotational spectrum of gaseous F2 has been used to determine a rotational constant of Bo=0.8841 ±0.0006 cm−1, corresponding to r0=1.4168±0.0005 Å.

scholarly journals Effect of annealing temperature on optical and electrical properties of metallophthalocyanine thin films deposited on silicon substrate

2016 ◽  
Vol 34 (3) ◽  
pp. 676-683 ◽  
Author(s):  
R. Skonieczny ◽  
P. Popielarski ◽  
W. Bała ◽  
K. Fabisiak ◽  
K. Paprocki ◽  
...  
Keyword(s):  
Thin Films ◽  
Raman Spectra ◽  
Silicon Substrate ◽  
Thin Layers ◽  
Excitation Wavelength ◽  
Type Silicon ◽  
Atomic Force ◽  
Before And After ◽  
Evaporation Technique ◽  
Polarized Raman

AbstractThe cobalt phthalocyanine (CoPc) thin films (300 nm thick) deposited on n-type silicon substrate have been studied using micro-Raman spectroscopy, atomic force spectroscopy (AFM) and I-V measurement. The CoPc thin layers have been deposited at room temperature by the quasi-molecular beam evaporation technique. The micro-Raman spectra of CoPc thin films have been recorded in the spectral range of 1000 cm-1 to 1900 cm-1 using 488 nm excitation wavelength. Moreover, using surface Raman mapping it was possible to obtain information about polymorphic forms distribution (before and after annealing) of metallophthalocyanine (α and β form) from polarized Raman spectra. The I-V characteristics of the Au/CoPc/n-Si/Al Schottky barrier were also investigated. The obtained results showed that influence of the annealing process plays a crucial role in the ordering and electrical conductivity of the molecular structure of CoPc thin films deposited on n-type silicon substrate.

Resonance Raman Spectra of Aqueous Pollen Suspensions with 222.5–242.4-nm Pulsed Laser Excitation

1991 ◽  
Vol 45 (2) ◽  
pp. 307-311 ◽  
Author(s):  
R. Manoharan ◽  
E. Ghiamati ◽  
K. A. Britton ◽  
W. H. Nelson ◽  
J. F. Sperry
Keyword(s):  
Raman Spectra ◽  
Laser Excitation ◽  
Resonance Raman ◽  
Pulsed Laser ◽  
Resonance Raman Spectra

Performance of a Spatial-Filter-Equipped Single Monochromator for Raman Spectroscopy

1994 ◽  
Vol 48 (6) ◽  
pp. 720-723 ◽  
Author(s):  
Mark O. Trulson ◽  
Horst B. Lueck ◽  
Donald M. Friedrich
Keyword(s):  
Raman Spectroscopy ◽  
Laser Excitation ◽  
Scattered Light ◽  
Spatial Filtering ◽  
Spatial Filter ◽  
Stray Light ◽  
Ultraviolet Region ◽  
Excitation Wavelength ◽  
Excitation Light ◽  
Diffuse Background

A technique for reducing stray-light artifacts in Raman spectroscopy is described. The performance of a spatial filter at the output of a single monochromator is reported. The filter reduces both the diffuse background and the scattered-light artifacts encountered in single monochromators while maintaining high luminous throughput. Unlike other wavelength-selective methods for rejecting laser-excitation light (such as use of holographic edge or notch filters), spatial filtering of scattering artifacts may be used with any excitation wavelength. This is an advantage for Raman spectroscopy in the quartz ultraviolet region where holographic filters are not yet available. The enhanced ability to observe low-wavenumber scattering with an optical multichannel detector on a single monochromator is a particular advantage of the method.

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