基于1.6μm甲烷气体吸收线的半导体激光器频率稳定性分析

利用波长调制技术以及数字PI控制器将外腔二极管激光器（ECDL）稳定到1.6 μm处的甲烷气体吸收线上.稳定后的激光频率波动小于5.6 MHz,相对于自由运转时的160 MHz有了很大提高, 而误差信号的Allan方差均方根（即稳定度）在平均积分时间为64 s时达到最小值1.66×10－11.从理论上定性分析了频率稳定度受到的各种限制因素,最后得出本实验中频率稳定度主要受频率调制和探测器噪声限制的结论,同时给出了提高频率稳定度的方法.被稳定的激光器主要用于为甲烷气体浓度监测提供频率参考.     

高效液相色谱法测定玉米面馒头中着色剂柠檬黄

建立了用高效液相色谱仪测定玉米馒头中柠檬黄的方法.分析柱为Symmetry Shield RP18(3.9 mm ×150mm,5μm),流动相为甲醇-乙酸铵(体积比18:72),流速为0.6 mL/min,检测波长为254 nm,流动相直接提取样品待测组分上机检测.该条件下柠檬黄测定结果的相对标准偏差为2.2%(n=...     

n维简并理想费米气体的化学势和热容量

对能谱为ε＝ａｐ＾３的ｎ维简并理想费米气作了统一讨论，给出它的费米能、有限温度下的化学势、内能以及热容量的表达式。     

甲烷气体2ν_3带R9支吸收线强度的精确测量

通过外腔二极管激光器测量了甲烷位于 16 37.6 4～ 16 37.85nm(真空中 )的 2ν3 带R9支的直接吸收谱 ,通过Voigt拟合计算出了每条线的吸收线强度 ,并与Margolis用傅里叶变换红外光谱仪测得的实验结果进行了比较 ,同时分析了偏差及产生的原因。实验和计算得出 ,在测得的八条吸收线中 ,最大偏差为 3.9% ,最小偏差为 0 .0 2 % ,除了线 3和线 4有较大偏差外 ,其他结果都在实验误差范围之内。所获得的数据可应用于光学遥测甲烷气体浓度。提供的方法也可应用到CO ,CO2 ,NH3 等其他气体的吸收线强度的测量中。     

Formation of ordered arrays of oriented polyaniline nanoparticle nanorods

We report the preparation of ordered polyaniline (PANI) nanorod arrays in an aqueous medium. The oriented PANI nanorods (80-400 nm in diameter and 8-15 mum in length) were synthesized in the presence of hydrophilic Allura Red AC (ARAC) as the structure-directing agent and ammonium persulfate as an oxidant in HCl solution. The morphologies of the oriented PANI nanoparticle nanorods were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy images, and the effect of reaction conditions on the morphology of PANI nanostructures was also studied. On the basis of the result obtained from small-angle X-ray scattering, we propose that rodlike micelle arrays of ARAC-aniline are responsible for directing the formation of oriented PANI nanoparticle nanorods. SEM images and the data analysis of static and dynamic light scattering give supportive evidence to the formation of the PANI nanoparticle nanorods by an elongation process. The chemical and electronic structures of the PANI nanorods were also studied by Fourier transform IR and UV-vis spectrometries, respectively.     

Mass-analyzed threshold ionization spectroscopy of the rotamers of p-n-propylphenol cations and configuration effect

Two-color resonant two-photon mass-analyzed threshold ionization (MATI) spectroscopy was used to record the vibrationally resolved cation spectra of the selected rotamers of p-n-propylphenol. The adiabatic ionization energies of the trans, gauche-A, and gauche-B rotamers are determined to be 65 283+/-5, 65 385+/-5, and 65 369+/-5 cm(-1), which are less than that of phenol by 3342, 3240, and 3256 cm(-1), respectively. This suggests that the n-propyl substitution causes a greater degree in lowering the energy level in the cationic than the neutral ground state. Analysis on the MATI spectra of the selected rotamers of p-n-propylphenol cation shows that the relative orientation of the p-n-alkyl group has little effect on the in-plane ring vibrations. However, the low-frequency C(3)H(7) bending vibrations appear to be active only for the two gauche forms of the cation.     

Mass-analyzed threshold ionization spectroscopy of p-methylphenol and p-ethylphenol cations and the alkyl substitution effect

The mass-analyzed threshold ionization (MATI) spectra of p-methylphenol and p-ethylphenol have been recorded by ionizing via various vibronic levels. The adiabatic ionization energies (IEs) of p-methylphenol and p-ethylphenol are determined to be 65918+/-5 and 65628+/-5 cm(-1), which are less than that of phenol by 2707 and 2997 cm(-1), respectively. This redshift indicates that the interaction between the alkyl group and the ring of alkylphenols in the cationic D(0) state is greater than that in the neutral S(0) state. Moreover, a longer alkyl group gives rise to a greater redshift in the IE. Analysis of the MATI spectra shows that most of the active modes are related to the in-plane ring vibrations of these two cations. However, the length of the alkyl group has an insignificant effect on the frequency of the observed ring vibrations. No band with frequency less than 350 cm(-1) is observed for the p-methylphenol cation. In contrast, many low-frequency bands resulting from the characteristic motions (e.g., the C-C(2)H(5) torsion and C-C(2)H(5) and C-OH bending vibrations) appear in the MATI spectra of p-ethylphenol. The present results show that the ethyl group enhances the substituent-sensitive and many large-amplitude vibrations of the cation.     

双模SU(1,1)相干态光场与V-型三能级原子玻色-爱因斯坦凝聚体相互作用系统中光场的压缩特性

在双模SU(1,1)相干态光场和V-型三能级原子玻色-爱因斯坦凝聚体相互作用系统中,应用全量子理论,在旋波近似下,研究了双模光场的压缩特性,分别讨论了光场与原子之间的耦合常数、原子之间的相互作用和光场参数对光场压缩特性的影响.研究表明,光场的两个正交分量均被周期性压缩,光场与原子的耦合系数和原子间的相互作用强度增大时均使得光场正交分量涨落的周期缩短;光场参数的变化不影响光场压缩的周期,对压缩深度有一定的影响.     

Probing outer-sphere adsorption of aqueous metal complexes at the oxide-water interface with resonant anomalous x-ray reflectivity

Resonant anomalous x-ray reflectivity near the Pt L(III) edge simultaneously revealed the geometric and spectroscopic structures of Pt(NH(3))(4)(2+) ions adsorbed at the quartz(100)-water interface. The derived Pt geometric subprofile shows two discrete "outer-sphere" adsorbed layers, and the interface-specific x-ray absorption edge profile exhibits a significant white-line enhancement compared to the bulk-solution species.     

Quantitative image reconstruction of GaN quantum dots from oversampled diffraction intensities alone

The missing data problem, i.e., the intensities at the center of diffraction patterns cannot be experimentally measured, is currently a major limitation for wider applications of coherent diffraction microscopy. We report here that, when the missing data are confined within the centrospeckle, the missing data problem can be reliably solved. With an improved instrument, we recorded 27 oversampled diffraction patterns at various orientations from a GaN quantum dot nanoparticle and performed quantitative image reconstruction from the diffraction intensities alone. This work in principle clears the way for single-shot imaging experiments using x-ray free electron lasers.