Measurement of the Rb D2 transition linewidth at ultralow temperature

The Rb D2 linewidth was studied using atoms cooled to a temperature of 50 μK that were contained in a magneto-optical trap. The transmission of a probe laser through the atom cloud was monitored using a CCD detector. The frequency of the probe laser was scanned across the resonance using an acousto-optic modulator. The observed lineshape was very well fitted by a Lorentzian function. The full width half maximum linewidth was examined as a function of the optical depth and the probe laser intensity. The extrapolated value at zero optical depth 6.062 ± 0.017 MHz corresponds to a 5P_3/2 lifetime of 26.25 ± 0.07 ns. This result agrees with lifetimes found in experiments that measured the temporal decay of fluorescence or photoassociation spectroscopy and is somewhat below the result of a relativistic many body perturbation calculation.     

Rotational analysis and line intensities of the HCO B^2A＇-X^2A＇31^1 band at 296 K

This paper computes the rotational energy levels of the HCO B^2A＇-X^2A＇31^1 transition, especially, the higher values of the rotational quantum numbers NKa Kc and Ka, with the rotational constants which are obtained via B3LYP method with 6-311G basis set, and the results show that the calculated frequencies using the computed vibration-rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO.     

Integrated 25 GHz and 50 GHz spectral line width dense wavelength division demultiplexer on single photonic crystal chip

We propose a new integrated demultiplexer model using the two-dimensional photonic crystal (2D PC) through the hexagonal resonant cavity (HRC) for the International Telecommunication Union (ITU) standard. The integrated model of demultiplexer for both 25 GHz and 50 GHz has been designed for the first time. The demultiplexer consists of bus input waveguide, drop waveguide, Hexagonal Resonant Cavity (HRC), 6 Air Hole Filter (6-AHF), 7 Air Hole Filter (7-AHF). The 7-AHF is used to filter 25GHz wavelength, and the 6-AHF filter is used to filter 50 GHz wavelength. The Q-factor on the designed demultiplexer is flexible based on the idea of increasing the number of air holes between drop waveguide and resonant cavity. The demultiplexer is designed to drop maximum 8 resonant wavelengths. One side of demultiplexer is able to drop 50 GHz ITU standard wavelengths, which are of 1556.3 nm, 1556.7 nm, 1557.1 nm and 1557.5 nm, and further the other facet is able to drop 25 GHz wavelengths, which are of 1551.4 nm, 1551.6 nm, 1551.8 nm, and 1552.0 nm. The proposed demultiplexer may be carried out within the integrated dual system. This system is able to lessen the architecture cost and the size is miniaturized substantially.     

二维矩形腔体中混合流体行进波对流

Rayleigh-Benard模型是研究对流稳定性,时空结构和非线性特性的典型模型之一。本文的兴趣集中在二维矩形腔体中混合流体对流场的结构方面。利用SIMPLE算法数值求解流体力学方程组,模拟了充分发展的二维矩形腔体中混合流体对流。结果说明偏离传导失去稳定的系统经过亚临界分叉产生了振动对流。进一步,我们给出了分叉曲线及其沿分叉曲线的上部分支三个Rayleigh数对应的对流图案的垂直速度场,流线,温度场,浓度场和Shadowgraph强度的等值线图。所有场的结构分析表明浓度场及Shadowgraph强度的等值线图可以很好的特征行进波的运动特性。     

苹果品质检测的可见-近红外激光漫反射光谱图像法的方法研究

利用可见-近红外激光漫反射光谱图像法及化学计量学方法检测了苹果的可溶性固形物含量和硬度。为了消除苹果形状对品质检测的影响,分析了5个不同波长的激光(680,780,880,940和980 nm)照射在富士苹果果面形成的光斑图像,并通过一系列图像处理方法得出了的苹果形状修正算法。分别利用修正前后的光谱图像参数建立苹果可溶性固形物含量和硬度的偏最小二乘回归(PLSR)模型,模型预测值和真实值之间的相关系数从0.78和0.80分别提高到0.87和0.89。为了消除果面镜面反射对苹果内部品质检测的影响,文章提出了象素强度频率检测法,并比较了利用果面光斑图像中光强均值和不同强度对应的象素强度频率建立的苹果硬度和可溶性固形物含量的PLSR模型效果,得出象素强度频率的模型效果更好。苹果可溶性固形物含量和硬度PLSR模型中预测均方根误差(RMSEP)分别从1.28°Brix和8.23 N.cm-2降低到0.84°Brix和6.17 N.cm-2。     

对称陀螺分子PH30010-0000跃迁带的高温线强度计算

通过直接计算分子配分函数并将常温下的无转动跃迁偶极矩平方近似为一常数应用到高温，计算了对称陀螺分子PH3 0010-0000跃迁的高温线强度。在296K，计算的分子总配分函数与HITRAN数据库的结果符合很好，只有-0.075%的百分误差。计算的跃迁线强度在2000 K和3000 K的高温与HITRAN数据库的结果也吻合较好，表明分子配分函数和线强度的高温计算是可靠的。在此基础上，进一步计算了更高温度4000和5000 K的跃迁线强度，报道了对称陀螺分子PH3 0010-0000跃迁在极端高温4000和5000 K的模拟光谱。计算结果对大气分子高温光谱的实验测量和理论研究均有一定的参考价值。