Raman scattering temperature effects

Attention should be paid to possible problems in the measurement of fluorescence quantum yields (some of which are discussed Section 6.1.5) inner filter effects, possible wavelength effects on Op, refractive index corrections, polarization effects, temperature effects, impurity effects, photochemical instability and Raman scattering. 

The work reported here shows that the transformation temperature in the LaVxNbi x04 system is significantly affected by the simple, partial substitution of one 5+ ion for another at the center of the tetrahedron. This effect is connected closely to the dynamical characteristics of the crystal lattice. A study involving inelastic neutron scattering, heat capacity and Raman scattering is under way in this Laboratory to clarify these aspects of the problem. 

Abstract Electronic correlation effects in La2.ISrINi04 lead to spontaneous phase separation into microscopic spin/charge stripes with commensurate or incommensurate order. Raman scattering experiments on such single crystalline materials show a rich phenomenology of phonon and magnon anomalies due to the new, self-organized periodicities. These effects are observable as function of temperature. 

The extremely small cross sections for conventional Raman scattering, typically 10 111 to 10-25 cm2/molecule has in the past precluded the use of this technique for single-molecule detection and identification. Until recently, optical trace detection with single molecule sensitivity has been achieved mainly using laser-induced fluorescence [14], The fluorescence method provides ultrahigh sensitivity, but the amount of molecular information, particularly at room temperature, is very limited. Therefore, about 50 years after the discovery of the Raman effect, the novel phenomenon of dramatic Raman signal enhancement from molecules assembled on metallic nanostructures, known as surface-enhanced Raman spectroscopy or SERS, has led to ultrasensitive single-molecule detection. 

Temperature from Rotational and Vibrational Raman Scattering Effects of Vibrational-Rotational Interactions and Other Corrections... 

Raman spectra have been obtained with a Jobin Yvon single monochromator equipped with a notch filter and a CCD detector cooled at liquid nitrogen temperature. Raman scattering has been excited through a He-Ne laser (632.8 nm) at low power (6 mW) to avoid heating effects. Spectra have been taken both in situ, that is during and after the deposition in an ultra high vacuum (UHV) chamber, and ex situ after the exposition of the deposited film to atmosphere. 

Carbon ion implantation has been used as a pretreatment process to control die nucleation of diamond particles on surgical alloy T1-6A1-4V substrates.l Carbon ions at 30 keV were implanted at room temperature into masked r ons on the substrates, up to doses of 10 -7 x 10 ions cm . The SEM, microfocus Raman scattering and RBS analyses of diamond nucleation in MW PACVD indicated that the carbon ion implantation was very effective in controlling diamond nucleation on Ti-6A1-4V, and diamond nucleation density depended on ion dose. The carbon ion implantation gave rise to (a) a decrease in diamond nucleation density, up to 8 times smaller than that on the substrate polished with 0.25 pm diamond paste (2-5 x 10 17C 7 7 X 106 o.m-21- rh)... 

Temperature and pressure effects on azides have been studied with the emphasis being on the alkali-metal salts of relatively simple structure. Phase transitions have been observed, but studies of the dynamics of the transitions have only recently been started via Raman scattering experiments. These aspects are reviewed below. 

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