基于混合漫射近似的空间分辨漫反射光学参量灵敏度的研究

根据空间分辨漫反射的双点源混合漫射近似模型, 推导了空间分辨漫反射率对生物组织吸收系数μ_a和有效散射系数μ'_s灵敏度的解析表示, 系统研究了在强吸收条件近光源区域吸收系数μ_a和有效散射系数μ'_s对漫反射光子分布的影响. 研究表明: 吸收系数的灵敏度随光源与探测器间距ρ的增加呈线性增长, 其斜率正比于(μ'_s/μ_a)^1/4, 比例系数约为1.4, 同时获得一个优化的探测距离ρ_opt, 距离光源约3.4个输运平均自由程, 在这个距离处有效散射系数的变化对测量吸收的影响最小. 这项研究对于生物组织的光学性质测量以及漫反射光谱技术的应用具有重要意义.     

Studies in molecular structure,symmetry and conformation—Part XIV. Crystal and molecular structure of L-isoleucine hydrochloride monohydrate form II

The crystal structure of a new form of L-isoleucine hydrochloride monohydrate C₆H₁₃O₂NHClH₂O (termed form II) has been determined using three-dimensional photographic data. This differs conformationally from the hydrochloride derivative (termed form I, Trommel and Bijvoet 1954) reported earlier. The crystal belongs to the orthorhombic space group P2₁2₁2₁ with cell dimensions,a=5.87±0.01,b=24.77±0.02 andc=6.85±0.01 ? and four molecules per cell,ρ _obs=1.240 g/cm³,ρ _cal=1.238 g/cm³,μ for CuKa=32.6 cm⁻¹. Contribution No. 420 from the Department of Crystallography and Biophysics, University of Madras, Madras 600025.     

SiO2分子的基态(X1A1)结构与分析势能函数

应用群论及原子分子反应静力学方法推导了SiO₂分子的电子态及其离解极限，采用B3P86方法，在6-311G^**水平上,优化出SiO₂基态分子稳定构型为单重态的C_2V构型，其平衡核间距R_e=R_Si—O=0.1587 nm,∠OSiO＝111.2°,能量为-440.4392 a.u..同时计算出基态的简正振动频率:对称伸缩振动频率ν(B₂)=945.4cm^-1，弯曲振动频率ν(A₁)=273.5 cm^-1和反对称伸缩振动频率ν(A₁)=1362.9cm^-1.在此基础上，使用多体项展式理论方法，导出了基态SiO₂分子的全空间解析势能函数，该势能函数准确再现了SiO₂(C_2V)平衡结构.     

Nd掺杂对Bi4Ti3O12铁电薄膜的微结构和铁电性能的影响

利用溶胶-凝胶法在Pt/Ti/SiO₂/Si(100)衬底上制备了Nd掺杂Bi₄Ti₃O₁₂(Bi_4-xNd_xTi₃O₁₂, x=0.00,0.30,0.45,0.75,0.85,1.00,1.50)铁电薄膜样品.研究了Nd掺杂对Bi₄Ti₃O₁₂薄膜的微结构和铁电性能的影响.研究结果表明:Nd掺杂未改变Bi₄Ti₃O₁₂薄膜的基本晶体结构.在掺杂量x<0.45时,Nd³⁺只取代类钙钛矿层中的A位Bi³⁺.当x=0.45时,样品剩余极化强度达最大值,在270kV·cm^-1的电场下为32.7μC·cm^-2.掺杂量进一步增加时,结构无序度开始明显增大,Nd³⁺开始进入(Bi₂O₂)²⁺层,削弱其绝缘层和空间电荷库的作用,导致材料剩余极化逐渐下降.当掺杂量x达到1.50时,掺杂离子最终破坏(Bi₂O₂)²⁺层的结构,材料发生铁电-顺电相变.     

LiNbO3和LiTaO3晶体Er3+/Yb3+掺杂水热外延层室温吸收光谱分析

本文引入与浓度和厚度有关的k_NL待定参数, 在J-O理论基础上, 对Er³⁺/Yb³⁺掺杂的LiNbO₃和LiTaO₃单晶衬底上 的多晶水热外延样品进行了基于吸收光谱的拟合计算. LiNbO₃:Ω₂=2.34× 10^-20 cm², Ω₄=0.77× 10^-20 cm², Ω₆=0.31×10^-20 cm², k_NL=4.32× 10^-2 mol·m^-2. LiTaO₃:Ω₂=1.68×10^-20 cm², Ω₄=0.84×10^-20 cm², Ω₆=0.45×10^-20 cm², k_NL=9.17×10^-3 mol· m^-2. 该方法可尝试推广到粉体或胶体等难以直接获得浓度和厚度数据的体系. 经上转换发光测试及光谱参数计分析认为Er³⁺/Yb³⁺离子的掺杂浓度比为1:1的情况下, 样品呈现绿色上转换发光光谱; 可尝试以降低基质声子能量的方法提高⁴I_13/2能级 对²H_11/2和⁴S_3/2能级的量子剪裁效率.     

掺铒铋酸盐玻璃的光谱性质研究

研究了掺铒铋酸盐玻璃的吸收和荧光光谱性质,应用Judd-Ofelt理论计算了玻璃的三个强度参量Ω_t=(t=2,4,6),分别为Ω₂=3.71×10^-20cm²,Ω₄=1.86×10^-20cm²,Ω₆=1.28×10^-20cm²,计算了Er³⁺离子的自发跃迁几率、荧光分支比等光谱参量.经荧光谱测试发现掺Er³⁺铋酸盐玻璃的荧光半高宽可达70nm.应用McCumber理论计算1.53μm处的受激发射截面可达9×10^-21cm².对Er³⁺离子在不同基质玻璃中光谱特性的比较发现,Er³⁺在铋酸盐玻璃中具有相对较高的受激发射截面和宽的荧光半高宽.     

氮化钒的选态双色可见紫外共振增强光电离和脉冲场光电子研究 (cited: 4)

对气态氮化钒(VN)分子在光子总能量为56900～59020 cm^-13∏0, v'=0)的单转动态, 然后再被紫外激光电离．这样的双色激光模式可以测量电子态、振动态和转动态都被选择和解析的氮化钒阳离子VN⁺(X²△; v⁺=0, 1, 2)光谱． 通过对转动解析的PFI-PE光谱模拟分析, 确定J⁺=3/2为基态离子态的最低转动能级, 从而确认VN⁺的基态电子态为²△_3/2．通过对VN+(PFI-PE)光谱的分析得到如下物理量的精确数值：VN⁺(X²△_3/2)的绝热电离能为IE(VN)=56909.5±0.8 cm^-1(7.05588±0.00010 eV),振动常数ω_e⁺=1068.0±0.8 cm^-1,反常振动常数ω_e⁺χ_e⁺=5.8±0.8 cm^-1;VN⁺(X²△_3/2)的转动常数B_e⁺=0.6563±0.0005 cm^-1,α_e⁺=0.0069±0.0004 cm^-1,平衡键长为1.529 ?;VN⁺(X²△_5/2)的转动常数B_e⁺=0.6578±0.0028 cm^-1,α_e⁺=0.0085±0.0028 cm^-1,平衡键长为1.527 ?;X²△_5/2,3/2自旋轨道耦合常数A=153.3±0.8 cm^-1     

BeCl分子电子激发态的多参考组态相互作用计算

运用含Davidson修正的多参考组态相互作用方法,在aug-cc-pVTZ基组水平上,对BeCl分子基态和相同多重度的几个低电子激发态进行了势能扫描计算.通过群论原理确定各电子态对称性及离解极限.将其中基态(X²Σ⁺)和第一激发态(A²Π})对应的势能曲线拟合到Murrell-Sorbie解析势能函数形式,得到基态(X²Σ⁺)的离解能及主要光谱常数(括号中为文献[6]提供的实验值)为D_e=3.74eV,R_e=0.18173nm(0.17970),w_e=857.4cm¹(847.2),w_ex_e=5.03cm^-1(5.14),B_e=0.7103cm^-1(0.7285),α_e=0.0059cm^-1(0.0069),第一激发态(A²Π)的D_e=3.02eV,R_e=0.18369nm(0.18211),w_e=832.7cm^-1(822.1),w_ex_e=5.93cm^-1(5.24),B_e=0.6953cm^-1(0.7094),α_e=0.0065cm^-1(0.0068),计算结果与实验值符合得较好.另外,通过Level程序求解双原子径向核运动的Schrödinger方程得到J=0时BeCl分子这两个电子态的全部振动能级.     

宽带腔增强吸收光谱技术应用于痕量气体探测及气溶胶消光系数测量

基于氙灯的非相干宽带腔增强吸收光谱系统, 并将其应用于痕量气体及气溶胶消光系数的测量. 该系统的探测灵敏度通过测量NO₂在520—560 nm波长范围内的吸收得到验证, 最小可探测灵敏度为1.8× 10^-7cm^-1 (1σ, 0.12 s积分时间, 50次平均), 对应的NO₂探测极限～33 nmol/mol. 结合标准气溶胶粒子发生系统, 测量了不同浓度的单分散硫酸铵气溶胶粒子在532 nm波长处的消光系数, 得到粒径为600 nm的硫酸铵气溶胶的消光截面为1.12× 10^-8cm², 与文献报道值1.167× 10^-8cm²相一致, 验证了气溶胶测量的可行性和准确性.     

碘分子两个新的“E”带离子对态

使用脉冲光学双共振方法研究了碘分子“E”带离子对态,激发光总能量范围为43180—43600cm^-1。实验获得了“E”带两个尚未见报道的离子对态E₁(13≤V′_(E1)≤17)和E₂(15≤V′_(E2)≤19),其中T_(e1)=41909.13±1.786cm^-1,T_{(e相似文献}   

基于delta-P1近似模型的空间分辨漫反射一阶散射参量灵敏度研究

以delta-P1近似光学模型为基础, 推导了双点源近似下空间分辨漫反射一阶散射参量μ_s'灵敏度的解析式, 并进行了数值分析和比较. 研究表明, 与混合漫射近似模型和漫射近似模型相比, delta-P1 近似模型能更好地描述强散射较强吸收情况下近光源区域生物组织漫反射光子的分布, 且在有效反照率a'>0.83时, 获得最佳优化距离ρ_opt, ρ_opt 随μ_s' 的增大而减小, 且在距光源约2.7—4个输运平均自由程处μ_s'的变化对测量吸收的影响最小. 这项研究对于优化传感器几何结构以及生物组织光学参量的测量具有重要意义.     

Investigation of structural and optical properties of 100 MeV F7+ ion irradiated Ga10Se90-xAlx thin films

Present work focuses on the effect of swift heavy ion (SHI) irradiation of 100 MeV F⁷⁺ ions by varying the fluencies in the range of 1 × 10¹² to 1 × 10¹³ ions/cm² on the morphological, structural and optical properties of polycrystalline thin films of Ga₁₀Se_90-xAl_x (x = 0, 5). Thin films of ~300 nm thickness were deposited on cleaned Al₂O₃ substrates by thermal evaporation technique. X-ray diffraction pattern of investigated thin films shows the crystallite growth occurs in hexagonal phase structure for Ga₁₀Se₉₀ and tetragonal phase structure for Ga₁₀Se₈₅Al₅. The further structural analysis carried out by Raman spectroscopy and scanning electron microscopy verifies the defects or disorder of the investigated material increases after SHI irradiation. The optical parameters absorption coefficient (α), extinction coefficient (K), optical band gap (E_g) and Urbach’s energy (E_U) are determined from optical absorption spectra data measured from spectrophotometry in the wavelength range 200–1100 nm. It was found that the values of absorption coefficient and extinction coefficient increase while the value of optical band gap decreases with the increase in ion fluence. This post irradiation change in the optical parameters was interpreted in terms of bond distribution model.     

Measurements of optical parameters of phantom solution and bulk animal tissues in vitro at 650 nm

Optical parameters of bulk animal tissue in vitro, including absorption coefficient (μ_a), reduced scattering coefficient (μ′_s) or scattering coefficient (μ_s), total attenuation coefficient (μ_t), anisotropy factor (g) and refractive index (n) are measured at wavelength of 650 nm. Clinical Intralipid-10% is diluted in distilled water into different concentrations to use as tissue phantoms. Four types of animal tissues in vitro are studied. The relationships among the optical parameters are analyzed systemically. For animal tissues, μ_a, μ′_s or μ_s and n rely on muscle fiber orientations. μ_s and μ_t range from 10 to 20 mm⁻¹, μ_a from 10⁻² to 10⁻³ mm⁻¹ and g from 0.95 to 0.99.     

Optical phonons in CuAlS2

The optical phonons at k=0 of CuAlS₂ have been investigated by Raman scattering, infrared reflectivity and absorption measurements from 50 to 1000 cm^-1 at T=300 K. Eleven of the thirteen expected optically active phonons have been observed and identified with respect to their symmetry types. The phonon frequencies appear in a range from 498 to 76 cm^-1 with predominant polar modes at 445 and 266 cm^-1. The dielectric dispersion for E ⊥ c and E ∥ c has been determined by Kramers-Kronig integrations.     

MgF2单晶的THz光谱研究

利用THz时域光谱技术对MgF₂晶体(样品1)和MgF₂：Co晶体(样品2)在0.5—2.5 THz的吸收特性进行了研究.在0.5—2.5 THz波段，样品1吸收系数α(ν)随频率ν增加而增大，最大值为24 cm^-1.样品2的吸收系数比样品1大得多，Co掺杂使晶格吸收带边向低频移动，而且样品2在1.9 THz有吸收峰，吸收系数达到70 cm^-1，由此求出F^--Co²⁺离子键伸缩振动的键力常数K为3.40×10^-2　N/cm.这一结果表明，THz光谱分析有可能成为研究晶体化学键的一种重要手段.利用光学常数之间的关系计算了两个样品在0.5—2.5 THz的介电函数的实部ε₁(ν)，得到样品1的ε₁(ν)值在4.67至4.73之间，样品2的ε₁(ν)值在4.62至5.01之间. 关键词： THz辐射 光谱 2晶体')" href="#">MgF₂晶体     

Characterization of evaporated selenide semiconductor alloy on p-type substrates

The properties of chalcogenides that are most important for applications as infrared transmitting materials are reported and their mutual relationships are given. Si₅Se₈₀In₁₅ films were produced by means of thermal evaporation. The refractive index and the optical energy gap were determined by transmission measurements. Parameters considered in this study are density, molar volume, transition temperatures, electrical properties, infrared transmission, extinction coefficient and refractive index. This composition has no extrinsic and intrinsic absorption between 14 and 20 μm and the value of absorption coefficient is estimated lower than 10⁻³ cm⁻¹ at 10.6 μm. This glass is also suitable for infrared optical elements. A p-n junction is observed due to evaporated thin film of alloy on p-type Ge substrate.     

MgB2各向异性光学性质的第一性原理研究

使用密度泛函第一性原理研究了超导体MgB₂单晶各向异性的光学性质.在描述光学性质的基本理论和计算方法的基础上,计算了MgB₂的光电导谱、反射谱以及电子能量损失谱,并通过MgB₂的各个原子分解态密度图对所得到的反射谱和损失谱的各个谱峰做了详尽地分析.从光电导谱上来看,x方向与z方向有着很大差别,而在反射谱与电子能量损失谱中,x方向与z方向的特征峰位置都是相互符合的.从光导谱来看,沿 关键词： 超导体 电子结构 光学性质     

Optical parameters measurement for diagnostic and photodynamic therapy of human cervical adenocarcinoma (HeLa) cell line

The purpose of this study was to investigate the optical properties, absorption coefficient (μ _a ) scattering coefficient (μ _s ) and refractive indices, (n) of HeLa cell line in a suspension of 2% minimum essential medium (MEM) at two different (632.8 and 532.0 nm) wave lengths of laser light. Optical properties were determined with Kubelka Munk Model (KMM) and refractive index measurement was made through minimum angle of deviation method (MAD). We reported μ _a = 8.643 ± 0.187 and 2.348 ± 0.249 cm⁻¹ and μ _s = 5.609 ± 0.287 and 88.166 ± 2.833 cm⁻¹ at 632.8 and 532.0 nm, respectively. Refractive index was found to be 1.332 and 1.312 at 632.8 nm and 532.0 nm, respectively. The discussed results provide a route of information for clinical diagnosis, therapeutic application and dosimetry studies in HeLa and other cell lines.     

Absolute absorber quantification in turbid media at small source–detector separations

The aim of our studies was to develop a method to determine the absorption coefficient of a turbid medium in a reflection geometry with small source–detector separations. Therefore, the time-integrated microscopic Beer–Lambert law (MBL) was modified in order to obtain the absolute absorption coefficient from mean time of flight and dc-intensity measurements. The new technique was evaluated using turbid phantoms having varying scattering (μ_s ^′ between 0.2 and 2.2 mm^-1) and absorbing properties (μ_a between 0.04 and 0.14 mm^-1), comparable to many biological tissues at various source–detector separations between 3 and 11 mm. The measurements were performed at a wavelength of 1064 nm. We found that this new method was able to determine the absolute absorption coefficient of the selected phantoms with a standard error of less than 0.005 mm^-1 over the range of optical properties investigated. Received: 23 November 2001 / Revised version: 28 February 2002 / Published online: 14 May 2002     

Visible,near-infrared and infrared optical properties of silica aerogels

Silica aerogel is an excellent thermal insulation material with a low thermal conductivity and a high porosity and has attracted great concern in applications. This paper was to experimentally investigate the optical properties of optically thick silica aerogel in the visible, near-infrared and infrared spectrum region. The fiber-loaded silica aerogel sample was prepared through sol–gel technique and supercritical drying process. Silica fibers were added into the aerogel during the preparation procedure to strength the skeleton of aerogel. As a comparison with the fiber-load silica aerogel, a silica fiber composite sample with the same chemical component and different physical structure was also prepared. A simplified two-flux model neglecting the boundary effect was used to describe the radiation propagation characteristics inside the samples. The spectral normal-hemispherical reflectances, transmittances, and normal emittances of silica aerogel and silica fiber samples were measured and compared in the wavelengths of 0.38–15 μm. Then the spectral optical constants of samples were determined using the experimental data. The spectral absorption and scattering coefficients of silica aerogel were within (0.01 cm⁻¹, 31.0 cm⁻¹) and (1.4 cm⁻¹, 25.8 cm⁻¹). The results showed that the spectrum region where the scattering coefficient is low usually corresponds to a high absorption coefficient. In addition, the total radiation properties of samples were predicted at high temperatures. The analysis of optical properties of silica aerogel is necessary to provide valuable data in applications.