Er3+/Yb3+共掺碲钨酸盐玻璃的光谱性质和热稳定性的研究

制备了Er³⁺和Yb³⁺共掺的碲钨酸盐玻璃样品65TeO₂-25 WO₃-10R_mO_n(R_mO_n=PbO,BaO),(65+x)TeO₂-(25-x)WO ₃-10La₂O₃ (x=0,5,10), (60+x)TeO₂-(30 -x)WO₃-10Bi₂O₃ (x=0,5,10).测试了玻璃样品的吸收光谱、荧光光谱、能级寿命及热稳定性能.结果表明除含Bi ₂O₃的碲钨酸盐玻璃外，其余玻璃样品均没出现析晶开始温度(T_x)，说明碲钨酸盐 是一种适合于光纤拉制的玻璃基质材料.应用Judd-Ofelt理论计算了强度参数Ω_t(t=2, 4,6)，研究表明Ω₂在碲钨酸盐玻璃中主要受到Er-O键的共价性的影响，而Er^{3 +} 离子周围配位场的非对称性影响可以忽略.测得了Er³⁺在15 μm发射谱的荧光 半高宽 (FWHM=71—77nm)和Er³⁺的⁴I_13/2能级寿命 (τ^m=3—34 ms).应用McCumber理论计算了Er³⁺在15 μm处的受激发射截面(σ^peak=068—103×10^-20 cm²).比较了Er³⁺在不同玻璃基质里 的15 μm荧光带宽和发射截面，研究结果表明碲钨酸盐玻璃是一种制备宽带光纤放大器的理想基质材料.     

Inhomogeneity-free heteronuclear iMQC

Intermolecular dipolar interactions between proton and carbon spins can be used to indirectly detect carbon spectra with high sensitivity. In this communication, we present a modified sequence that, in addition to the high sensitivity of heteronuclear intermolecular multiple quantum coherence (iMQC) experiments, retains the line narrowing capability characteristic of homonuclear zero-quantum coherences. We demonstrate that this sequence can be used to obtain high resolution (13)C spectra in the presence of magnetic field inhomogeneities, both for thermal and hyperpolarized samples, and discuss applications to water-hyperpolarized carbon imaging.     

High sensitivity cw-cavity ringdown and Fourier transform absorption spectroscopies of CO2

The absorption spectrum of ¹³CO₂ has been recorded by cw-cavity ringdown spectroscopy with a new set up based on fibered DFB lasers. By using a series of 31 DFB lasers, the spectrum of carbon dioxide could be recorded in the 6130-6750 cm⁻¹ region with a typical sensitivity of 5 × 10⁻¹⁰ cm⁻¹. The spectrum has also been recorded between 4400 and 8500 cm⁻¹ with a Fourier transform spectrometer associated with a multi-pass cell (maximum path length of 105 m). The new observations obtained both by FTS and CRDS represent a significant extension of the available data. For instance, more than 4000 line positions were measured and assigned in the CRDS spectrum while only 232 line positions are listed in the HITRAN database. Altogether, the band by band analysis has led to the determination of the rovibrational parameters of 65, 7, and 24 bands for the ¹³C¹⁶O₂, ¹⁶O¹³C¹⁷O, and ¹⁶O¹³C¹⁸O isotopomers, respectively. As some observed line positions show significant deviations from the predictions of the effective Hamiltonian model, the new observed line positions were gathered with the data available in the literature to refine the set of effective Hamiltonian parameters of the ¹³C¹⁶O₂ isotopic species. The refined set of 96 effective Hamiltonian parameters reproduces more than 14 650 line positions of ¹³C¹⁶O₂ with an RMS=0.002 cm⁻¹. A detailed comparison with the line positions retrieved from Venus spectra and the line list provided by HITRAN is also presented and discussed.     

Fourier transform spectroscopy of the CO-stretching band of O-18 methanol

The high-resolution Fourier transform spectrum of the ν₈ CO-stretching band of CH₃¹⁸OH between 900 and 1100 cm⁻¹ has been recorded at the Canadian Light Source (CLS) synchrotron facility in Saskatoon, and the majority of the torsion-rotation structure has been analyzed. For the ν_t = 0 torsional ground state, subbands have been identified for K values from 0 to 11 for A and E torsional symmetries up to J values typically well over 30. For ν_t = 1, A and E subbands have been assigned up to K = 7, and several ν_t = 2 subbands have also been identified. Upper-state term values determined from the assigned transitions using the Ritz program have been fitted to J(J + 1) power-series expansions to obtain substate origins and sets of state-specific parameters giving a compact representation of the substate J-dependence. The ν_t = 0 subband origins have been fitted to effective molecular constants for the excited CO-stretching state and a torsional barrier of 377.49(32) cm⁻¹ is found, representing a 0.89% increase over the ground-state value. The vibrational energy for the CO-stretch state was found to be 1007.49(7) cm⁻¹. A number of subband-wide and J-localized perturbations have been seen in the spectrum, arising both from anharmonic and Coriolis interactions, and several of the interacting states have been identified.     

复宗量厄米-高斯光束的相干模表示

基于激光的相干模分解理论，讨论了复宗量厄米_高斯(EHG)光束的模相关和相干模表示，推导出EHG光束的模相关系数的解析表达式，并给出了一种只包含有限个模式的相干模表示. 在此基础上，根据EHG光束的模结构，分析了EHG光束和常规厄米_高斯(SHG)光束M²因子的差异. 关键词： 复宗量厄米_高斯(EHG)光束 相干模分解 2因子')" href="#">M²因子 模相关系数(MCCs)     

可紫外激光刻写的掺铒铋硅酸盐玻璃光谱性质研究

报道了可紫外激光刻写的掺铒Na₂O-Bi₂O₃-SiO₂和Na₂O-B₂O₃-Bi₂O₃-SiO₂玻璃的光谱特性. 测量和计算了玻璃的光谱参数，分析、讨论了Bi₂O₃和B₂O₃含量变化对光谱参数的影响.实验表明基质玻璃中Bi₂O₃和B₂O₃含量改变可有效调节掺铒铋硅酸盐玻璃光谱参数.Bi₂O₃和B₂O₃含量增加，玻璃的光吸收和荧光性质改善，但Er³⁺离子的⁴I_13/2能级寿命降低.在B₂O₃含量为40%(Bi₂O₃/SiO₂＝0.67)时，Er³⁺离子峰值发射截面、⁴I_13/2能级的荧光寿命和荧光半高宽分别为8.49×10^－21cm²，0.52ms和78nm.结果表明掺铒铋硅酸盐玻璃是有前途的紫外光敏有源玻璃材料之一.     

O(3P)+1，2-丁二烯反应的交叉分子束和理论研究：丙烯+CO和亚乙基+乙烯酮反应的主要分子通道

详细了解O(~3P)与不饱和烃的多通道燃烧反应机理需要鉴定所有主要反应产物、确定分支比、评估三重态与单重态势能面之间的系间窜跃.将交叉分子束实验、软电离、质谱、飞行时间分析,以及高级从头算计算三重态/单线态势能面,RRKM/Master方程计算支化比包括系间窜跃,均可以获得最佳效果.最近已经证明这些方法对于含有两个或三个碳原子的最简单的不饱和烃(炔烃,烯烃,二烯)和O(~3P)反应是成功的.本文通过交叉分子束与理论相结合的方法研究O(~3P)和含有四个C原子的二烯类化合物,1,2-丁二烯(甲基芳烃)的反应,探索产物分布、分支比和系间窜跃如何随着分子复杂性的增加而变化,即从O(~3P)和丙二烯反应到O(~3P)1,2-丁二烯的反应变化.尤其关注了最重要的导致链终止的主导分子通道(即形成丙烯+CO(分支≥0.5)和亚乙基+乙烯酮(分支比≥0.15))与导致链传递的自由基形成通道进行对比(分支比≥0.35).     

共掺Na+的Yb3+∶CaF2晶体的荧光分析与低阈值激光运转

基于975nm激发的室温下荧光光谱测量，系统地研究了在新型钠、镱共掺的氟化钙晶体中钠离子的作用机理，分析了掺钠离子浓度与激光阈值的关系，获得了具有最低激光阈值的掺杂浓度优化配比. 激光实验表明对于2%Yb³⁺离子浓度的氟化钙，掺入3%的钠离子能够获得最低阈值的激光运转，这与理论和荧光分析完全一致. 关键词： 镱、钠共掺氟化钙 荧光光谱 激光阈值     

Water vapor absorption line intensities in the 1900-6600 cm region

Water vapor infrared spectra have been measured using the Bruker IFS 120 HR Fourier transform spectrometer at the Physikalisch-Chemisches Institut of the Justus-Liebig-Universität Giessen. Spectra were recorded at pressure-broadening-limited resolution and at room temperature in the range of 1900-6600 cm⁻¹. The use of fully evacuated transfer optics and a White-type multireflection cell made it possible to obtain pressure×pathlength products up to 31.27 mbar×288.5 m. These spectra have previously been used to determine experimental values of rovibrational line positions and upper energy levels of the 2ν₂, ν₁, and ν₃ bands [Mikhailenko SN, Tyuterev VlG, Keppler KA, Winnewisser BP, Winnewisser M, Mellau G, et. al. The 2ν₂ band of water: analysis of new FTS measurements and high-K_a transitions and energy levels. J Mol Spectrosc 1997;184: 330-49] and of the 3ν₂, ν₁+ν₂, and ν₂+ν₃ bands [Mikhailenko SN, Tyuterev VlG, Starikov VI, Albert KK, Winnewisser BP, Winnewisser M, et al. Water spectra in the region 4200-6250 cm⁻¹, extended analysis of ν₁+ν₂, ν₂+ν₃, and 3ν₂ bands and confirmation of highly excited states from flame spectra and from atmospheric long-path observations. J. Mol. Spectrosc. 2002; 213: 91-121].This work presents the intensities of 3769 lines for the weak and medium transitions in the spectral range indicated. These data provide an independent source of experimental information which is complementary to intensity data available in the literature and can thus help to evaluate experimental errors and the reliability of these spectral line parameters.     

Dynamical structure of peptide molecules: Fourier transform microwave spectroscopy of N-methylpropionamide

In order to clarify the dynamical aspects of the peptide structure, N-methylpropionamide (NMPA) was investigated as an example of peptide molecules: XCONHY (X=CH₃CH₂ and Y=CH₃ for NMPA), paying special attention to the internal rotation of the two methyl groups. NMPA was found to have an almost planar skeleton with an extended syn/trans conformation, as indicated by the observed value of I_aa+I_bb−I_cc, and its rotational spectra were interpreted in terms of group G₁₈ consisting of six symmetry species: A₁, A₂, E₁, E₂, E₃, and E₄. The A₁ and E₂ spectra were observed split in most of b-type transitions, yielding the internal-rotation potential barrier V₃ of 796 (21) cm⁻¹ for CH₃ in the ethyl group referred to as C-CH₃. The spectra of the three E species: E₁, E₃, and E₄ appeared several tens to thousands MHz apart from the corresponding A₁ spectra, suggesting the internal-rotation potential barrier of CH₃ bonded to the nitrogen, called N-CH₃, to be quite low. In sharp contrast with the A₁ spectra, which were well fitted to the ordinary asymmetric-rotor spectral pattern, a few higher-order terms were required to reproduce the E₁ spectra, presumably because of the low N-CH₃ barrier. The spectral analysis thus performed, in fact, led to the V₃ of 80.06487 (14) cm⁻¹, an order of magnitude lower than that of C-CH₃. The E₃ and E₄ spectra were found to form triplets with the corresponding E₁ lines at the center, and the E₃-E₁ and E₄-E₁ splittings were explained essentially by the contributions of the C-CH₃ internal rotation combined with the kinetic-energy coupling between the two methyl groups. The torsion around the C-C bond between the ethyl and carbonyl groups was suggested by an ab initio calculation to be of double minimum nature, but the observed A₁ spectra did not show any indication of such a double-minimum potential for the C-C torsion, although the possibility of a small hump being present at a planar conformation could not be entirely eliminated. The present results on NMPA along with those obtained on other peptide molecules will be of some significance in clarifying important problems of structural biology such as protein folding and signal transfer through biological systems.     

掺铒高硅氧玻璃光谱性质的研究

应用Judd-Oflet理论计算了新型掺铒高硅氧玻璃中铒离子的强度参量Ω_t(t=2,4,6)，Ω₂=8.15×10^-20，Ω₄=1.43×10^-20，Ω₆=1.22×10^-20，相比于其他氧化物玻璃，表现出较大的Ω_2,6值，反映了铒离子周围的近邻结构不对称性和Er-O键的离子键成分较高.利用McCumber理论计算得到了能级^{关键词： 掺铒高硅氧玻璃 Judd-Ofelt理论 量子效率}     

The pure rotational spectrum of TiS (XΔr) at submillimeter wavelengths

The pure rotational spectrum of TiS in its X³Δ_r ground state has been measured using millimeter-wave direct-absorption techniques in the frequency range of 313-425 GHz. This free radical was created by the reaction of titanium vapor, produced in a high-temperature Broida-type oven, with H₂S. Eight to ten rotational transitions were recorded for the main titanium isotopologue, ⁴⁸TiS, in the v = 0 and v = 1 levels, as well as for the v = 0 state of ⁴⁶TiS, observed in natural abundance (⁴⁸Ti:⁴⁶Ti = 74:8). All three Ω components were observed in almost every recorded transition, with no evidence for lambda-doubling. The data were fit with a Hund’s case(a) Hamiltonian, and rotational, spin-orbit, and spin-spin constants were determined, as well as equilibrium parameters for ⁴⁸TiS. Relatively few fine structure parameters were needed for the analysis of TiS (A, A_D, and λ), unlike other 3d metal species. The rotational pattern of the three fine structure components suggests the presence of a nearby excited ¹Δ state, lying ∼3000 cm⁻¹ higher in energy. From the equilibrium parameters, the dissociation energy for TiS was estimated to be ∼5.1 eV, in reasonable agreement with past thermochemical data.     

Spectral and Computational Studies on Benzil Mono-(2-Pyridyl)Hydrazone

In the present study, structural properties of Mono-(2-Pyridyl) Hydrazone were studied extensively utilizing density functional theory (DFT) employing B3LYP exchange correlation. The Fourier transform infrared (solid phase) was recorded. The vibrational frequencies in the ground state were calculated by using density functional method (B3LYP) with 6-31G* and 6-311G** as basis sets. The spectral studies revealed that the title compound exists in Keto form. Spectral techniques that we employed include ¹H and ¹³C NMR, electronic, thermal techniques. Correlation between experimental chemical shifts and GIAO/B3LYP/6-311G**-calculated isotropic shielding constants, δ_exp = a + bσ_calc, are reported. Good linear regressions between experimental and theoretical results for ¹H and ¹³C were obtained.     

The He scattering and reactions on C and cluster states of C

The ⁶He+¹²C elastic and inelastic scattering and the ⁶He+¹²C→α+¹⁴C reaction have been measured using a 18.0 MeV ⁶He beam. Experimental results for the elastic scattering are in fair agreement with optical model predictions, using the potentials found in the analysis of ⁶Li scattering on ¹²C at similar energies. In triple coincidences, the ⁶He+¹²C→¹⁰Be+2α reactions were clearly seen, with the ¹⁰Be nucleus left in ground and several excited states. The dominant mechanism of this reaction is sequential decay through cluster states of ¹⁴C.     

Pr3+离子单掺LiLuF4单晶的坩埚下降法生长及光谱性能研究

本文应用坩埚下降法技术在全密封铂金坩埚条件下生长了不同Pr³⁺离子掺杂浓度的高质量LiLuF₄单晶. 测定了单晶体从420 nm至500 nm的激发光谱. 在446 nm光激发下,观察到单晶体480 nm(³P₀→³H₄)蓝色发射带、522 nm(³P₁→³H₅)绿色发射及605 nm(¹D₂→³H₄)的红色发射,其对应的平均寿命分别为38.5、37.3和36.8 μs. 其荧光寿命明显大于Pr³⁺掺杂的氧化物单晶. 同时研究了激发波长和掺杂浓度对发射强度以及色度坐标的影响. 获得最佳的Pr³⁺浓度为∽0.5 mol%,并分析了环境温度从298 K 到443 K变化对荧光强度的影响. 结果表明随着温度的增加,荧光强度逐步变弱,其中³P₀→³H₄(480 nm)能级跃迁受温度影响最大,其次是³P₁→³H₅和¹D₂→³H₄.     

High-resolution infrared spectroscopy of H12C13CD and H13C12CD in the 470–5200 cm−1 spectral region

The fundamental ro-vibrational bands and the 2ν₄?←?GS, 2ν₅?←?GS, 2ν₃?←?GS, ν₄?+?ν₅?←?GS, ν₃?+?ν₄?←?GS, ν₃?+?ν₄?←?ν?₄, ν₃?+?ν₅?←?ν₅, overtone, combination and hot bands of the two rare isotopologues of acetylene H¹²C¹³CD and H¹³C¹²CD have been detected by Fourier transform infrared spectroscopy (FTIR). The analysis of the data has provided very accurate rotational and vibrational parameters for the ground and for the vibrationally excited states.     

转动诱发原子核量子相变的一种可能途径

基于微观IBM理论,提出转动诱导出玻色子量子相变的一种可能途径:一旦原子核在受到高能激发或作快速旋转时,假如外界提供的能量足以使玻色子完成拆对顺排,则核处于集体相与单粒子态的共存相,其特征是出现较密集的能谱;假如能量不足以完成拆对或顺排,可能发生两种情况之一,当核旋转达到某个临界转动频率ω_c时,或者一个高角动量的玻色子脱离“集体”而“游离”出来,或者发生一个高角动量的玻色子转变为一个低角动量的玻色子,核仍旧处于集体相;均会伴随出现光辐射,产生基态带的一条能级——相变信号.正是这类玻色子相变导致了原子核的量子相变.本物理图像统一了玻色子拆对顺排相变和退耦释放光子相变的描述.以¹⁰⁰Pd核的14⁺₁,14⁺₂和14⁺₃态的产生机理为例,对模型作了仔细说明.     

The ν1 + 3ν2 + 3ν3 and 4ν1 + ν2 + ν3 bands of ozone by CW-cavity ring down spectroscopy between 5900 and 5960 cm

The absorption spectrum of ozone, ¹⁶O₃, has been recorded in the 5903-5960 cm⁻¹ region by high sensitivity CW-cavity ring down spectroscopy (α_min ∼ 5 × 10⁻¹⁰ cm⁻¹). The ν₁ + 3ν₂ + 3ν₃ and 4ν₁ + ν₂ + ν₃ A-type bands centred at 5919.15 and 5947.07 cm⁻¹ were newly observed. A set of 173 and 168 energy levels could be experimentally determined for the (1 3 3) and (4 1 1) states, respectively. Except for a few K_a = 5 levels of the (4 1 1) state, the rotational structure of the two states was found mostly unperturbed. The spectroscopic parameters were determined from a fit of the corresponding line positions by considering the (1 3 3) and (4 1 1) states as isolated. The determined effective Hamiltonian and transition moment operators were used to generate a list of 785 transitions given as Supplementary Material.     

Luminescent properties of (Y,Gd)BO3:Bi,RE (RE=Eu, Tb) phosphor under VUV/UV excitation

Bi³⁺- and RE³⁺-co-doped (Y,Gd)BO₃ phosphors were prepared and their luminescent properties under vacuum ultraviolet (VUV)/UV excitation were investigated. Strong red emission for (Y,Gd)BO₃:Bi³⁺,Eu³⁺ and strong green emission for (Y,Gd)BO₃:Bi³⁺,Tb³⁺ are observed under VUV excitation from 147 to 200 nm with a much broader excitation region than that of single Eu³⁺-doped or Tb³⁺-doped (Y,Gd)BO₃ phosphor. Strong emissions are also observed under UV excitation around 265 nm where as nearly no luminescence is observed for single Eu³⁺-doped or Tb³⁺-doped (Y,Gd)BO₃. The luminescence enhancement of Bi³⁺- and RE³⁺-co-doped (Y,Gd)BO₃ phosphors is due to energy transfer from Bi³⁺ ion to Eu³⁺ or Tb³⁺ ion not only in the VUV region but also in the UV region. Besides, host sensitization competition between Bi³⁺ and Eu³⁺ or Tb³⁺ is also observed. The investigated phosphors may be preferable for devices with a VUV light 147-200 nm as an excitation source such as PDP or mercury-free fluorescent lamp.     

Manifestations of hyperfine interaction in optical spectra of KY3F10:Ho

We report on the first observation of the well-resolved hyperfine structure in optical spectra of the KY₃F₁₀:Ho³⁺ single crystals. Some interesting peculiarities of this structure and the origin of the observed forbidden transitions are discussed.