Temperatures from rotational-vibrational raman Q-branches

An iterative, least-squares analysis scheme, based on the differential of the intensity, dI = dτ?I/?τ + d? ?I/?? has been developed for obtaining the temperature θ = 1/τ and density ? from a set of rotational-vibrational Raman, Q-branch intensities. Spectral locations that cover the maximum variation in ?I/?τ were determined from a set of computed intensities and derivatives. The results for the Stokes (anti-Stokes) bands indicate for temperatures less than 2100K (2700K) that the maximum extent of ?I/?τ can be spanned by recording intensities only in the first two vibrational bands, v(1-0) and v(2-1) and, due to the multivalued nature of ?I/?τ, equally spaced values for ?I/?τ can be obtained only by programming the spectrometer to select an appropriate set of non-uniformly spaced passbands.     

Evaluation of critical exponents from raman intensities

Theory and experiment are compared for Raman intensities near continuous structural phase transitions. Situations in which the order parameter couples linearly to light or quadratically are considered. Both cases are easily analyzed for the soft modes in ferroelastic LnP₅O₁₄ (Ln = La, Pr, Nd, Tb). The trace polarizability tensor yields β = 0.49 ± 0.02; off-diagonal terms give γ’ = 1.16 ± 0.15 and γ = 1.07 ± 0.10. Mean field results are also obtained for barium sodium niobate near T (incommensurate) = 582 K and for tris-sarcosine calcium chloride near T _c = 128 K.     

Orientation dependence of surface enhanced raman intensities: results from abinitio calculations

Time dependent Hartree—Fock methods have been used to calculate Raman intensifies for H₂ adsorbed onto a model lithium cluster as a function of the orientation of H₂ relative to the cluster surface. The intensity is found to be largest for perpendicular adsorption, dropping to a small value at an intermediate angle, and then rising to a second but smaller maximum for parallel adsorption. The results are interpreted using a model which correlates enhancement to lithium cluster orbital energy shifts induced by the static quadrupole field Of H₂.     

低起始温度的线性升温热处理对直拉硅中氧沉淀的影响

研究了直拉硅片从不同的温度线性升温(Ramping)到750℃，然后在750℃退火64 h过程中的氧沉淀行为. 结果表明，Ramping对硅片中氧沉淀的形成有明显的促进作用，且起始温度越低促进作用越强. 这是因为在Ramping处理中，低温(450—650℃)热处理阶段氧的扩散速率显著增强，促进了氧沉淀核心的形成，且较低的Ramping升温速率有利于氧沉淀核心的稳定和继续长大. 进一步的实验结果还表明，低起始温度的Ramping处理可应用于硅片的内吸杂工艺，能促进氧沉淀的生成提高硅片的内吸杂能力，减少热预     

低起始温度的线性升温热处理对直拉硅中氧沉淀的影响

研究了直拉硅片从不同的温度线性升温(Ramping)到750℃,然后在750℃退火64 h过程中的氧沉淀行为. 结果表明,Ramping对硅片中氧沉淀的形成有明显的促进作用,且起始温度越低促进作用越强. 这是因为在Ramping处理中,低温(450—650℃)热处理阶段氧的扩散速率显著增强,促进了氧沉淀核心的形成,且较低的Ramping升温速率有利于氧沉淀核心的稳定和继续长大. 进一步的实验结果还表明,低起始温度的Ramping处理可应用于硅片的内吸杂工艺,能促进氧沉淀的生成提高硅片的内吸杂能力,减少热预 关键词： 直拉硅 氧沉淀 退火     

Irreversible loss of adatoms on Ag electrodes during potential cycling determined from surface enhanced raman intensities

Surface enhanced Raman scattering of adsorbates (Ag⁰-Cl^?, H₂O and pyridine) on Ag electrodes in 1M KC1 and 1M KCl+0.05M pyridine electrolytes was monitored continuously with an optical multichannel analyzer system as the electrode potential was cycled over various ranges within nonfaradaic regions of the oxidation-reduction cycle. A systematic investigation was performed of the potential dependence of SERS of pyridine in 1M KX + 0.05M pyridine electrolytes, where X = F, Cl, Br and I. Since the surface coverage of the adsorbates is reversible with potential cycling within a potential range, it was possible to determine potential dependences of the irreversible loss in the SERS enhancement factor which occurs as the electrode potential is ramped toward the potential of zero charge (PZC). The results provide strong support for the role of adatoms on the electrode surface in the overall enhancement mechanism. There is evidence that the strongly bound adsorbates immobilize the adatoms at positive potentials but allow the adatoms to migrate and become lost at surface defects as the potential approaches the PZC where the adsorbates are less tightly bound.     

Effect of particle size on excitation of vibrational modes at low temperatures

The application of a long wavelength limit to Debye theory is examined for small particles at low temperatures. The questions of choice and validity of cut-off are examined, as well as sources of error in the general theory of small particles. An approximate expression is given for the specific heat and Mössbauer recoil-free fraction, with curves showing magnitudes of this effect for various functional relations. Several other possible applications are mentioned.     

The dipole moment derivatives and charge flux parameters from vibrational absorption intensities of ethylene oxide

The signs of dipole moment derivatives for ethylene oxide obtained from ab initio calculations using the 6-31G¹ basis set are presented. From these signs and the experimental vibrational absorption intensity data, the atomic polar tensor elements and bond charge flux parameters were evaluated. These quantities were compared with those in the literature calculations employing approximate signs and force constants.     

Analysis of band intensities in vibrational spectra of esters and deuteroesters

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 4, pp. 570–574, April, 1991.     

Cars measurement of vibrational temperatures in electric discharges

The measurement of vibrational and rotational temperatures of D₂ at the center of an electrical discharge has been demonstrated by a new diagnostic technique: Coherent Anti-Stokes Raman Spectroscopy (CARS). On the assumption of equilibration among vibrational levels, T_v was estimated to be approximately 1050 K, whereas T_r was determined to be near ambient (?400 K).     

Transient stimulated raman scattering in crystals during motion of populations of vibrational states

Transient stimulated Raman scattering (SRS) in crystals is analyzed taking into account the motion of populations of vibrational states under the action of subpicosecond (shorter than the dephasing time) pump pulses. Analytic expressions describing the dynamics of excitation of vibrations in SRS are derived. It is found that for a small wavelength of SRS interaction and high intensities of pump radiation observed for femtosecond SRS in crystals, avalanche excitation of vibrations can be responsible for SRS suppression. It is shown that when phase matching of Stokes-anti-Stokes parametric coupling in transient SRS is ensured, it is possible to elevate the efficiency of frequency conversion under conditions of motion of populations of vibrational states; this explains recent successful results in the experimental implementation of femtosecond SRS in crystals pumped by a Bessel beam.     

基于火焰发射光谱的转动温度和振动温度的测量

利用光学多通道分析仪(OMA)对酒精和煤油在大气中燃烧时的火焰发射光谱进行了分析.实验发现上述火焰发射光谱在275-600 nm波段范围内存在多支辐射强度很大的带状分子光谱,其中以OH自由基A²Σ⁺→X²Π_r(300-330 nm),CH自由基A²Δ→X²Π(410-440 nm)和C₂自由基A³Π_g→X³Π_u(500-520 nm)电子带系的发射光谱最为强烈.实验中采用高分辨率光栅对OH自由基A²Σ⁺→X²Π_r和CH自由基A²Δ→X²Π电子带系发射光谱的精细结构进行了分析.与此同时,本文基于分子光谱理论计算了不同转动温度和振动温度条件下OH自由基A²Σ⁺→X²Π_r和CH自由基A²Δ→X²Π电子带系发射光谱的强度分布,同时通过理论计算光谱和实验光谱进行比较确定了酒精燃烧火焰的转动温度和振动温度. 关键词： 火焰发射光谱 谱线强度 转动温度 振动温度     

Density effects on the spectral intensities of dielectronic satellite line in dense plasmas

Summary In this paper we present a theoretical analysis of the spectral intensity of dielectronic satellite lines in dense plasmas. The ion microfield causes an oscillator strength mixing that alters the spectral intensity of such a transition. Numerical calculations of this high-density effect have been performed for the most intense 2l2l′→1s2l He-like transitions.

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Riassunto In questo articolo si presenta un'analisi teorica dell'intensità spettrale delle linee di satellite dielettroniche in plasmi densi. Il microcampo ionico causa un mescolamento delle forze dell'oscillatore che modifica l'intensità spettrale di una tale transizione. Si sono effettuati calcoli numerici di questo effetto ad alta densità per le transizioni più intense del tipo 2l2l′→1s2l.

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Резюме В этой работе мы предлагаем теоретический анализ спектральной интенсивности диэлектронных линий сателлитов в плотной плазме. Микрополе иона вызывает смешивание сил осцилляторов, что изменяет спектральную интенсивность такого перехода. Проведены численные вычисления эффекта высокой плотности для наиболее интенсивных Не-подобных переходов 2l2l′→1s2l.