Effective dipole moment parameters of C2H2 for the 100, 7.7, 1.4, 1.3, 1.2 and 1.0 μm regions

Based on new line intensity measurements collected from the literature, the effective dipole moment parameters of acetylene have been found for the 100, 7.7, 1.4, 1.3, 1.2 and 1 μm spectral regions by least-squares fittings. On average, the experimental uncertainty was obtained in all fits. The new sets of the effective dipole moment parameters combined with those that were previously published allow for the calculation of the line intensities for the majority of the acetylene bands in the spectral range from 100 to 1 μm.     

Infrared absolute intensities of ozone in the 10 and 5 μm spectral range: New investigations

Infrared high resolution spectra of ozone ¹⁶O₃ have been recorded in the 10 and 5 μm spectral ranges in order to derive their absolute intensities with a best achievable accuracy. Spectra have been recorded with the home made stepping mode FTS of GSMA (Reims). In the two spectral regions, we use UV-IR crossed beam cell. The quantification of ozone is achieved using UV cross section at 253.65 nm. A check of this UV calibration is also performed using direct pressure measurements of quasi-pure samples of O₃. The intensities are derived from infrared spectra using multifit procedure already tested. In the 10 μm range, where 12 different spectra have been recorded, 65 well selected lines led to a good agreement (better than 0.3%) with the HITRAN 2008 (or 2004) values, confirming our previous work [De Backer-Barilly MR, Barbe A. Absolute intensities of the 10 μm bands of ¹⁶O₃. J Mol Spectrosc 305:2001;43-53]. In the 5 μm range, where 18 transitions are selected, we also note a correct agreement with HITRAN 2008, despite a slightly larger averaged value between (1.9%) experimental and theoretical (HITRAN). As conclusion, authors suggest the use of current HITRAN 2008 data for atmospheric retrievals.     

Line intensities in the 1.5-μm spectral region of acetylene

Line intensities are measured for 546 transitions belonging to 13 bands of the main isotopologue ¹²C₂H₂ of the acetylene molecule, in the 1.5-μm spectral domain. A multispectrum fitting procedure is used to retrieve line parameters from Fourier transform spectra. Prior to this work, line intensities were known for only 4 bands in this spectral region, from the work of El Hachtouki and Vander Auwera [Absolute line intensities in acetylene: the 1.5 μm region. J Mol Spectrosc 2002;216:355-62]. An excellent agreement is found with the results of these authors, showing that the accuracy of both results is likely better than 1% for the strong bands. However, the spectrum becomes very crowded when one wants to study weaker bands, so that the average accuracy of the intensities reported in the present work is 5%. From these data, vibrational transition dipole moments squared and Herman-Wallis coefficients have been determined for all the bands.     

New infrared integrated band intensities for HC3N and extensive line list for the ν5 and ν6 bending modes

The infrared spectrum of cyanoacetylene (also called propynenitrile) has been investigated from 400 to 4000 cm⁻¹ at a resolution of 0.5 cm⁻¹. Integrated intensities of the main bands and a number of weaker bands have been obtained with an uncertainty better than 5%. Inaccurate values in previous studies have been identified in particular concerning the intensity of the strong ν₅ stretching band at 663.2 cm⁻¹. Former results on the temperature dependence of integrated intensities have also been revisited.Synthetic spectra calculation has been performed for the ν₅ and ν₆ bands on the basis of the best available high resolution data. It has been shown that the GEISA line parameters for HC₃N are not sufficient to reproduce the band intensities and some hot band features observed in our experimental spectra at room temperature. As a first step, the model spectra has been improved by including a number of missing hot subbands and by calculating accurately the hot band relative intensities. Finally, a perfect agreement between calculated and observed spectra was achieved on the basis of a global analysis of HC₃N levels up to 2000 cm⁻¹ combined with the new integrated intensity measurements. A new extensive line list for the ν₅ and ν₆ bending modes of HC₃N has been compiled.     

The 1.58 μm transparency window of methane (6165-6750 cm): Empirical line list and temperature dependence between 80 and 296 K

The empirical line parameters of over 12,000 methane transitions have been obtained at 80 K in the 1.58 μm transparency window (6165-6750 cm⁻¹) which is of importance for planetary applications. This line list (WKC-80K) was constructed from high sensitivity spectra of normal abundance methane recorded by CW-Cavity Ring Down Spectroscopy at low temperature. The minimum intensity reported is on the order of 5×10⁻³⁰ cm/molecule. High resolution Fourier transform spectra have also been recorded using enriched CH₃D samples at 90-120 K in order to facilitate identification of monodeuterated methane features in the methane line list at 80 K. The CH₃D relative contribution in the considered region is observed to be much larger at 80 K than at room temperature. In particular, CH₃D is found dominant in a narrow spectral window near 6300 cm⁻¹ corresponding to the highest transparency region.Using a similar line list constructed at room temperature (Campargue A, Wang L, Liu AW, Hu SM and Kassi S. Empirical line parameters of methane in the 1.63-1.48 μm transparency window by high sensitivity Cavity Ring Down Spectroscopy. Chem Phys 2010;373:203-10.), the low energy values of the transitions observed both at 80 K and at room temperature were derived from the variation of their line intensities. Empirical lower states and J-values have been obtained for 5671 CH₄ and 1572 CH₃D transitions representing the most part of the absorbance in the region. The good quality of these derived energy values is demonstrated by the marked propensity of the corresponding CH₄ lower state J values to be close to integers. The WKC line lists at 80 K and room temperature provided as Supplementary Material allow one accounting for the temperature dependence of methane absorption between these two temperatures. The importance of the 80 K line list for the study of Titan and other methane containing planetary atmospheres is underlined and further improvements are proposed. The resulting information will advance the theoretical modeling of the methane spectrum in the 1.58 μm transparency window.     

Absorption and emission characteristics of Er3NbO7 phosphor: A comparison with ErNbO4 phosphor and Er:LiNbO3 single crystal

Er₃NbO₇ phosphor was synthesized by sintering a mixture of Er₂O₃ and Nb₂O₅ powder in a molar ratio of 3:1 at 1600 °C over 55 h. Optical absorption and emission characteristics of Er³⁺ ions in the calcined Er₃NbO₇ powder were investigated and discussed compared with ErNbO₄ phosphor and a Z-cut congruent Er (2 mol%):LiNbO₃ single crystal. The absorption and emission studies show that, due to different crystal structures, the spectroscopic properties of these niobates have some differences in spectral shape, peak position, and relative intensity, especially at 1.5 μm. The most obvious spectral feature of the Er₃NbO₇ is that the spectral structure of band instead of peak is observed in its absorption or emission spectrum due to the existence of local structural disorder and multiple Er³⁺ sites. The Er₃NbO₄ shows stronger upconversion emission than the single crystal but weaker than the ErNbO₄. Experimental results show that energy transfer upconversion and/or excited state absorption play a dominant role in the upconversion emissions, and, at higher pump level (>200 mW), the thermal effect becomes significant and results in drop of the upconversion intensity. The 1.5 μm lifetimes of Er³⁺ ion in the Er₃NbO₇, ErNbO₄ phosphor, and in the Er:LiNbO₃ crystal are measured to be ∼5.3, 2.0, and 2.4 ms, respectively. In combination with the measured Raman spectra, the quantum efficiency, multiphonon nonradiative decay rate, and theoretical radiative lifetime of the 1.5 μm emission of the two powder materials are expected. The differences in upconversion intensity and measured 1.5 μm lifetime between the three materials are explained qualitatively.     

Si-based erbium-doped light-emitting devices

We report on the fabrication and performance of Si-based light sources. The devices consist of MOS structures with erbium (Er)-doped silicon rich oxide (SRO) film as gate dielectric. The devices exhibit electroluminescence (EL) at 1.54 μm at room temperature with a 0.2% external quantum efficiency. These devices show a high stability due to the silicon excess in the film. The Er-doped SRO films have been introduced in a Si/SiO₂ Fabry-Perot Microcavity in order to increase the spontaneous emission rate, the extraction efficiency and the spectral purity at the resonant wavelength. The active medium in the cavity has been electrically pumped and the conduction mechanisms have been analyzed. The EL spectra have also been acquired and compared with photoluminescence (PL) ones for the same resonant cavity light-emitting device (RCLED). The EL and PL peak intensities of the on-axis emission at the resonant wavelength are over 20 times above that of the similar Er-doped SRO film without a cavity. The Si-based RCLEDs exhibit different quality factors, ranging from 60 to 170. The spectra shape and intensity have been correlated with the quality factor. A high directionality of the emitted light, due to the presence of the resonant cavity, has also been observed: the overall luminescence is confined within 10° cone from the sample normal.     

Optical properties of Er:SrMoO4 single crystal

Er³⁺:SrMoO₄ crystal of high optical quality was grown by the Czochralski method. The room temperature polarized absorption and emission spectra together with the lifetime decay curve were measured. Based on the Judd-Ofelt theory, three intensity parameters, radiative transition rates, radiative lifetimes and fluorescent branching ratios, were obtained. Emission cross-section and gain cross-section around 1.54 μm were also obtained.     

基于光谱分析的油料池火内部传热特性研究

油料池火焰内部分为不同燃烧区域,目前对油池火内部传热特性研究较少。针对油池火内部传热特性研究不足的现状,构建了红外火焰光谱测试系统,研究分析了92#汽油、95#汽油及润滑油池火焰红外光谱特性,对油池火焰不同燃烧区域的光谱信息进行了提取分析,结果表明：三种油料池火焰光谱特征相似,存在多个CO₂,H₂O及炭黑颗粒等燃烧产物的特征发射波段,3.4 μm处C—H伸缩振动峰明显;火焰烟气区主要光谱特征为4～4.5 μm波段范围内高温CO₂发射峰,该区域火焰与空气换热剧烈,温度变化不稳定,火焰脉动频率较高;火焰间歇区的光谱特征是4～4.5 μm波段范围内高温CO₂发射峰,与烟气区相比,火焰间歇区脉动频率相对较低;与烟气区及间歇区相比,火焰连续区燃烧较为稳定,该区域的光谱特征明显,在2.5～3 μm波段范围内炭黑粒子发射光谱强度较高,且在3.4 μm处存在C—H伸缩振动峰,表明油料池火焰光谱3.4 μm处的特征峰由高温油蒸汽产生。油池火焰不同燃烧区域光谱特征分析表明,油池火焰液态油表面的“富燃料层”吸收火焰传热,引起3.4 μm附近油蒸汽分子能级的改变。油池火焰不同燃烧区域发射光谱强度计算表明,火焰连续区的强度最大,其次为间歇区,火焰烟气区与空气对流强烈,测得的发射光谱强度最低。研究结果为火焰—油料传热模型的修正提供了参考。     

Temperature-dependent fluorescence characteristics of an ytterbium-sensitized erbium-doped tellurite glass

In this article, the 1.5 μm emission spectra corresponding to the ⁴I_13/2→⁴I_15/2 transition of Er³⁺ in tellurite glass are studied within the temperature from 8 to 300 K. The emission spectra of Er³⁺: ⁴I_13/2→⁴I_15/2 transition are also analyzed using a peak-fit routine, and an equivalent four-level system is proposed to estimate the stark splitting for the ⁴I_15/2 and ⁴I_13/2 levels of Er³⁺ in the tellurite glass. The results indicate that the ⁴I_13/2→⁴I_15/2 emission of Er³⁺ can exhibit a considerable broadening due to a significant enhance the peak a′, and b′ change, respectively, and the peaks of which are located at about 1507 and 1556 nm. A detailed study of temperature-dependent 1.5 μm emission spectra involving the change of the corresponding sub-bands shows that as the temperature decreases from 300 to 8 K, its line-shape becomes sharper and more intense (the full-width at half-maximum decreases from 59 to 38 nm). Temperature-dependent fluorescence intensities and the experimentally determined lifetimes are investigated; the results show that a decrease behavior of fluorescence intensities and lifetimes are observed for temperature from 8 to 300 K.     

Efficient field emission from coiled carbon nano/microfiber on copper substrate by dc-PECVD

Crystalline coiled carbon nano/micro fibers in thin film form have been synthesized via direct current plasma enhanced chemical vapor deposition (PECVD) on copper substrates with acetylene as a carbon precursor at 10 mbar pressure and 750 °C substrate temperature. The as-prepared samples were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). XRD pattern as well as selected area electron diffraction (SAED) pattern showed that the samples were crystalline in nature. SEM and HRTEM studies showed that as synthesized coiled carbon fibers are having average diameter ∼100 nm and are several micrometers in length. The as-prepared samples showed moderately good electron field emission properties with a turn-on field as low as 1.96 V/μm for an inter-electrode distance 220 μm. The variation of field emission properties with inter-electrode distance has been studied in detail. The field emission properties of the coiled carbon fibrous thin films are compared with that of crystalline multiwalled carbon nanotubes and other carbon nanostructures.     

Modification of erbium photoluminescence excitation spectra for the emission wavelength 1.54 μm in mesoscopic structures

Photoluminescence excitation (PLE) spectra for the emission wavelength 1.54 μm were studied for erbium-doped xerogels embedded in artificial opals and porous anodic alumina films. Opals were chosen with photonic stop-band in green spectral range, where excitation of 1.54 μm occurs most efficiently. In comparison to the structure erbium-doped titania xerogel/porous anodic alumina/silicon the photoluminescence excitation spectra for 1.54 μm emission wavelength significantly changes for the same xerogels embedded in artificial opals. Enhancement of erbium-related 1.54 μm emission was observed from the structure Fe₂O₃ xerogel/porous anodic alumina fabricated on silicon, having some incompletely anodized aluminium, under excitation with either the lasing source at 532 nm or xenon lamp. Evident difference in PLE spectra for erbium doped TiO₂ and Fe₂O₃ xerogels in porous anodic alumina is observed.     

傅里叶变换红外光谱测量热气体温度新方法初步研究

详细地讨论了分子转振光谱理论,总结了影响分子转振光谱结构和强度分布的因素,得知各谱线相对光谱强度(即归一化光谱)只与温度有关,其分布结构与温度一一对应。根据这种特性,文章提出了一种利用傅里叶变换红外光谱测量热气体温度的新方法。从HITRAN标准数据库中提取数据建立了一个测温数据库,并用4个不同温度的实测光谱数据对建立的测温数据库进行定标和检验。用定标后的测温数据库所得的测量温度与实测温度吻合得非常好。与目前常用的两种遥感测温方法(分子发射基带最大强度光谱测温法,分子转振光谱测温法)相比,该方法的优点是：物理过程简单,容易计算,精度高,是一种简单实用的方法。     

Temperature and concentration measurements in acetylene-nitrogen mixtures in the range 300–600 K using dual-broadband rotational CARS

Pure rotational coherent anti-Stokes Raman scattering (CARS) experiments have been performed in acetylene for temperatures ranging from 294 to 582 K, and in mixtures of acetylene and nitrogen in the mole fraction range of 0.06–0.32 for acetylene at room temperature. The experimental spectra are evaluated by a least-square fitting to libraries of theoretically calculated spectra using two different Raman linewidth models, one with and one without dependence on the rotational quantum number J. It is found that a J-dependent model is favourable, both regarding temperature measurements in pure acetylene, and simultaneous acetylene concentration and temperature measurements in different mixtures of acetylene and nitrogen. For the temperature measurements performed in pure acetylene the temperature inaccuracy is generally less than 2% when the J-dependent model for the Raman linewidths is used. It is found that fitting the value of the non-resonant susceptibility significantly improves the quality of the spectral fits and is a requirement for high temperature accuracy with the present model. The evaluated concentrations show a maximum error of 13% on a relative scale. Potential sources of systematical errors both regarding measured temperatures and acetylene concentrations are discussed. Received: 8 June 1999 / Revised version: 3 Spetember 1999 / Published online: 3 November 1999     

激光诱导钛产生等离子体的光谱分析及电子温度的测量

用Nd∶YAG激光器产生的1.06μm、10ns的脉冲激光激发钛靶,用光学多通道分析仪(OMAII)测量了钛等离子体的时间分辨发射光谱,记录并分析了在40ns~200ns延迟范围内438~448nm波段的钛等离子光谱,用一组钛原子谱线的相对强度计算了不同延迟时间下等离子体电子温度。     

Effects of thermal treatment on femtosecond laser fabricated diffraction gratings in polystyrene

We report the fabrication of efficient, buried diffraction gratings and micro-craters in bulk polystyrene using femtosecond laser direct writing technique. We recorded a maximum diffraction efficiency of 10% for a buried grating fabricated at 1 μJ energy, 1 mm/s speed, and a period of 30 μm. Buried micro-craters, with typical dimensions of ∼2 μm, were achieved at low energies and high scanning speeds. From the field emission scanning electron microscope studies, the observed emission is attributed as due to the inner surface modifications and the debris settled around the voids. The fabricated gratings subjected to heat treatment were tested for the diffraction efficiency and emission at different excitation wavelengths and the observed results are presented. Raman spectra collected from the femtosecond laser modified regions revealed the disappearance of few Raman modes at high peak intensities associated with incident Gaussian laser pulse. Potential applications of these luminescent micro-craters are highlighted.     

Validation of HNO3 spectroscopic parameters using atmospheric absorption and emission measurements

The improved database of HNO₃ spectroscopic parameters in the 600–950 cm^?1 spectral region presented in [Gomez L, Tran H, Perrin A, Gamache RR, Laraia A, Orphal J, et al. Some improvements of the HNO₃ spectroscopic parameters in the spectral region from 600 to 950 cm^?1. JQSRT 2008, in press] is tested by comparisons between calculations and atmospheric remotely sensed absorption and emission spectra. The line parameters in the 11.3 μm region are validated using ground-based Fourier transform solar absorption measurements, whereas those in the 13.1 μm region are successfully tested using balloon-borne atmospheric emission spectra. In both regions, the quality of the line parameters and the consistency between band intensities is confirmed through comparisons with emission spectra collected by the satellite-borne MIPAS instrument.     

Influence of Li dopants on thermoluminescence spectra of CaSO4 doped with Dy or Tm

Thermoluminescence emission spectra are presented for lithium doped variants of CaSO₄:Dy or CaSO₄:Tm dosimetry material. All three dopants (Li, Dy and Tm) variously introduce different changes in both the glow peak temperatures and the luminescence efficiency. In every case the emission signals display the line emission characteristic of the rare earth ions. At temperatures below ∼50 K the relative peak intensities differ for Dy and Tm doped samples, and there are small temperature shifts between the Dy:Li and Tm:Li co-doped materials. Above room temperature the rare earth ions do not show peak temperature movements when co-doped with lithium. However they do influence the peak temperature by ∼5 °C when they are the sole dopant. Inclusion of lithium dramatically moves the high temperature glow peak from ∼200 °C down to 120 °C. All these changes are consistent with a single defect model in which the trapping sites and luminescence occur within the complexes formed of the rare earth ion, an intrinsic sulphate defect and lithium. The evidence and rationale for such a model are presented. There is discussion which suggests that such defect complexes are the norm in thermoluminescence.     

CL study of yellow emission in ZnO nanostructures annealed in Ar and O2 atmospheres

The yellow emission of thermally treated undoped and In doped ZnO nanostructures was studied by the cathodoluminescence (CL) technique. CL spectra acquired at room temperature of the as-grown samples revealed two emissions at about 3.2 eV and 2.13 eV, corresponding to the near band edge and defect related emissions, respectively. On annealing the samples at 600  ^°C in Ar and O₂ atmospheres, the defect emission suffers a red shift, irrespective of the annealing atmosphere. This red shift is explained in terms of variations in the relative intensities of the two component bands centered at about 2.24 eV and 1.77 eV, which were clearly resolved in the CL spectra acquired at low temperature of the annealed samples. A decrease of the relative intensity of the yellow emission (2.24 eV) was observed for all thermally annealed samples. The annealing of zinc interstitial point defects is proposed as a possible mechanism to explain this intensity decrease.