Fourier transform spectroscopy of CH3OH: rotation-torsion-vibration structure for the CH3-rocking and OH-bending modes

High-resolution Fourier transform spectra of CH₃OH have been investigated in the infrared region from 930 to 1450 cm⁻¹ in order to map the torsion-rotation energy manifolds associated with the ν₇ in-plane CH₃ rock, the ν₁₁ out-of-plane CH₃ rock, and the ν₆ OH bend. Upper-state term values have been determined from the assigned spectral subbands, and have been fitted to power-series expansions to obtain substate origins and effective B-values for the three modes. The substate origins have been grouped into related families according to systematic trends observed in the torsion-vibration energy map, but there are substantial differences from the traditional torsional patterns. There appears to be significant torsion-mediated spectral mixing, and a variety of “forbidden” torsional combination subbands with |Δυ_t|>1 have been observed, where υ_t denotes the torsional quantum number (equivalent to υ₁₂). For example, coupling of the (υ₆,υ_t)=(1,0) OH bend to nearby torsionally excited (υ₇,υ_t)=(1,1) CH₃-rock and (υ₈,υ_t)=(1,1) CO-stretch states introduces (υ₆,υ_t)=(1,0)←(0,1) subbands into the spectrum and makes the ν₇+ν₁₂−ν₁₂ torsional hot band stronger than the ν₇ fundamental. The results suggest a picture of strong coupling among the OH-bending, CH₃-rocking, and CO-stretching modes that significantly modifies the traditional energy structure and raises interesting and provocative questions about the torsion-vibration identity of a number of the observed states.     

Photoluminescence characteristics of ZnTiO3: Bi nanocrystals

The photoluminescence properties of the Bi³⁺ in sol-gel derived ZnTiO₃ nanocrystals have been investigated. An ultra-violet emission at 360 nm and a visible emission band at 506 nm have been observed, originating from two kinds of emission centers. The former is ascribed to the ³P₁-¹S₀ transition of Bi³⁺ and the latter to the recombination of the electrons with the photo-generated holes trapped in the zinc vacancies. In all cases the latter contribution is predominant.     

非线性守恒方程的两种稳定化谱元方法

考虑非线性守恒方程的高阶数值解法,介绍了基于谱元法的两种稳定性方法,一种是谱粘性消去法(SVV),另一种是过滤法.在SVV方法中,我们推广并分析了传统的基于单区域的SVV算子的定义.在过滤法中,我们分析了SVV-H elm holtz过滤算子的性质.文中从分析和计算两方面对两种方法进行了比较,建立了两者之间的关系.最后通过一系列数值试验说明方法的有效性.     

正交变换在重积分中某些应用

正交变换是代数学的基本内容 ,其用途十分广泛 .重积分的计算往往存在技术性的困难 ,若利用“正交变换”的有关理论去解决某些重积分的计算问题是颇有功效的 .本文将以“正交变换”为工具 ,简洁的处理重积分的某些问题     

Li(AlxCo1-x)O2晶体中Co3+电子态的变化及对结构演化的影响

研究了应用于锂二次电池正极的新型高能量密度存贮材料Li(AlxCo1-x)O2 (x=01—05)的磁性.发现Al3+的掺杂可导致Co3+中d电子自旋态发生变化，即有部分d电子进入高自旋态.伴随Co3+中电子状态的改变，材料结构演化也发生了相应变化，表现为c/a比增大明显减缓，较好地解释了材料结构对Vegard定律的正偏离.这对材料的微观结构与性能设计具有重要意义. 关键词： 锂电池材料 Li（AlxCo1-x）O2 磁性 自旋态 结构演化     

利用模式的对称性研究光子晶体光纤的色散

由光子晶体光纤的对称性可以得到模式分布的对称性，根据模式的对称性选择适当的展开函数，可以使计算量大大减少。计算了六角结构光子晶体光纤的色散特性，得到了波长在1．55pm处色散为零时，光子晶体光纤的结构参量所满足的方程。     

Approximate confidence limits of the reliability performances for a cold standby series system

This paper is to investigate the approximate confidence limits of the reliability performances (such as failure rate, reliability function and average life) for a cold standby series system. The Bayesian approximate upper confidence limit of failure rate is obtained firstly, and next Bayesian approximate lower confidence limits for reliability function and average life are presented. The expressions for calculating Bayesian lower confidence limits of the reliability function and average life are also obtained, and an illustrative example is examined numerically by means of the Monte-Carlo simulation. Finally, the accuracy of confidence limits is discussed.     

Rotational spectra, conformational structures, and dipole moments of thiodiglycol by jet-cooled FTMW and ab initio calculations

The rotational spectra of three low-energy conformers of thiodiglycol (TDG) (HOCH₂CH₂SCH₂CH₂OH) have been measured in a molecular beam using a pulsed-nozzle Fourier-transform microwave spectrometer. To determine the likely conformational structures with ab initio approach, conformational structures of 2-(ethylthio)ethanol (HOEES) (CH₃CH₂SCH₂CH₂OH) were used as starting points together with the consideration of possible intramolecular hydrogen bonding in TDG. Three lower-energy conformers have been found for TDG at the MP2=Full/6311G** level and ab initio results agree nicely with experimentally determined rotational constants. In addition, Stark measurements were performed for two of the three conformers for dipole moment determinations, adding to our confidence of the conformational structure matches between experimental observations and ab initio calculations. Of the three lower-energy conformers, one displays a compact folded-like structure with strong hydrogen bonding between the two hydroxyl groups and the central sulfide atom. Two other conformers have relatively open chain-like structures with hydrogen bonding between each of the hydroxyl groups to the central sulfur atom, of which one has pure b-type dipole moment according to the ab initio results.     

Monte Carlo ray-tracing simulation for radiative heat transfer in turbulent fluctuating media under the optically thin fluctuation approximation

The Monte Carlo ray-tracing method (MCRT) based on the concept of radiation distribution factor is extended to solve radiative heat transfer problem in turbulent fluctuating media under the optically thin fluctuation approximation. A one-dimensional non-scattering turbulent fluctuating media is considered, in which the mean temperature and absorption coefficient distribution are assumed and the shape of probability density function is given. The distribution of the time-averaged volume radiation heat source is solved by MCRT and direct integration method. It is shown that the results of MCRT based on the concept of radiation distribution factor agree with these of integration solution very well, but results of MCRT based on the concept of radiative transfer coefficient do not agree with these of integration solution. The solution of time-averaged radiative transfer equation by the concept of radiative transfer coefficient should be treated with caution.     

A diode-pumped passively Q-switched Nd:GdVO4 laser with a GaAs saturable absorption

We have demonstrated a passively Q-switched operation of Nd:GdVO₄ laser in which a GaAs crystal is used as the saturable absorber for the first time as far as we know. A maximum average output power of 1.64 W was obtained at an incident pump power of 12 W, the corresponding optical conversion efficiency and peak power were 13.7% and 116.8 W, respectively. The maximum peak energy obtained in the experiment by 50% transmission couple was 19 μJ.