The theory and experiment of solute migration caused by excited state absorptions

Nonsymmetrical transition from reverse-saturable absorption （RSA） to saturable absorption （SA） caused by excited state absorption induced mass transport of the CuPcTs dissolved in dimethyl sulfoxide is observed in an open aperture Z-scan experiment with a 21-ps laser pulse. The nonsymmetrical transition from RSA to SA is ascribed neither to saturation of excited state absorption nor to thermal induced mass transport, the so-called Sorer effect. In our consideration, strong nonlinear absorption causes the rapid accumulation of the non-uniform kinetic energy of the solute molecules. The non-uniform kinetic field in turn causes the migration of the solute molecules. Additionally, an energy-gradient-induced mass transport theory is presented to interpret the experimental results, and the theoretical calculations are also taken to fit our experimental results.

Full-Dimensional Potential Energy Surfaces of Ground(X^(2)A′)and Excited(A^(2)A″)Electronic States of HCO and Absorption Spectrum

In this work,high-fidelity full-dimensional potential energy surfaces(PESs)of the ground(X^(2)A′)and first doublet excited(A^(2)A″)electronic states of HCO were constructed using neural network method.In total,4624 high-level ab initio points have been used which were calculated at Davidson corrected internally contracted MRCI-F12 level of theory with a quite large basis set(ACV5Z)without any scaling scheme.Compared with the results obtained from the scaled PESs of Ndenguéet al.,the absorption spectrum based on our PESs has slightly larger intensity,and the peak positions are shifted to smaller energy for dozens of wavenumbers.It is indicated that the scaling of potential energy may make some unpredictable difference on the dynamical results.However,the resonance energies based on those scaled PESs are slightly closer to the current available experimental values than ours.Nevertheless,the unscaled high-level PESs developed in this work might provide a platform for further experimental and theoretical photodissociation and collisional dynamic studies for HCO system.

Ultrafast Excited State Dynamics of Biliverdin Dimethyl Ester Coordinate with Zinc Ions

As one of the biological endogenous pigments,biliverdin(BV)and its dimethyl ester(BVE)have extremely weak uorescence in solution with quantum yield less than 0.01%.However,the situation reverses with the addition of zinc ions.The strength for uorescence of BVE-Zn^2+ complex is greatly enhanced and uorescence quantum yield can increase to5%.Herein,we studied ultrafast excited state dynamics of BVE-Zn^2+ complex in ethanol,npropanol,and DMSO solutions in order to reveal the mechanism of uorescence quantum yield enhancement.The results show that BVE can form a stable coordination complex with zinc with 1:1 stoichiometry in solution.BVE is structurally and energetically more stable in the complex.Using picosecond time-resolve uorescence and femtosecond transient absorption spectroscopy,we show that smaller non-radiative rate constant of BVE-Zn^2+ complex in DMSO is the key to increasing its uorescence quantum yield and the excited state decay mechanism is also revealed.These results provide valuable information about the uorescence property change after BVE binding to metal ions and may provide a guidance for the study of phytochromes or other uorescence proteins in which BV/BVE acts as chromophores.

Long Chain Fatty Acid Affects Excited State Branching in Bilirubin-Human Serum Protein Complex

After binding to human serum albumin,bilirubin could undergo photoisomerization and photoinduced cyclization process.The latter process would result the formation of a product,named as lumirubin.These photo induced behaviors are the fundamental ofclinical therapy for neonatal jaundice.Previous studies have reported that the addition of long chain fatty acids is beneficial to the generation of lumirubin,yet no kinetic study has revealed the mechanism behind.In this study,how palmitic acid affects the photochemical reaction process of bilirubin in Human serum albumin(HSA)is studied by using femtosecond transient absorption and fluorescence up-conversion techniques.With the addition of palmitic acid,the excited population of bilirubin prefers to return to its hot ground state(S_(0))through a 4 ps decay channel rather than the intrinsic ultrafast decay pathways(<1 ps).This effect prompts the Z-Z to E-Z isomerization at the S_(0) state and then further increases the production yield of lumirubin.This is the first time to characterize the promoting effect of long chain fatty acid in the process of phototherapy with femtosecond time resolution spectroscopy and the results can provide useful information to benefit the relevant clinical study.

A TD-DFT Study for the Excited State Calculations of Microhydration of N-Acetyl-Phenylalaninylamide (NAPA)

Investigating the impact of microhydration on the excited-states and electronic excitation properties of biomolecules has remained one of the important yet challenging aspects of science because of the complexity of developing models. However, with the advent of computational chemistry methods such as TD-DFT, many useful insights about the electronic excitation energy and excited-state nature of biomolecules can be explored. Accordingly, in our study, we have incorporated the TD-DFT/wB97XD/cc-pVTZ method to study the excited state properties of N-acetyl phenylalanine amide (NAPA-A(H2O) n) (n = 1 to 4) clusters from ground to the tenth lowest gaseous singlet excited state. We found that the C=O bond length gradually increases both in N-terminal amide and C-terminal amide after the sequential addition of water molecules because of intermolecular H-bonding and this intermolecular H-bonding becomes weaker after the sequential addition of H2O molecules. The UV absorption maxima of NAPA-A (H2O)n (n = 1 - 4) clusters consisted of two peaks that are S5←S0 (1st absorption) and S6←S0 (2nd absorption) excitations. The first absorption maxima were blue-shifted with the increase in oscillator strength. This means that strong H-bonds reduce the charge transfer and make clusters more rigid. On the other hand, the second absorption maxima were red-shifted with the decrease in oscillator strength. In the ECD spectra, the negative bands indicate the presence of an amide bond and L-configuration of micro hydrated NAPA-A clusters. Finally, our calculated absorption and fluorescence energy confirm that all the NAPA-A (H2O) n (n = 0 - 4) clusters revert to the ground state from the fluorescent state by emitting around 5.490 eV of light.

Excited-State Nonlinear Photonic Devices Using Organic Materials

A Series of all-optical devices are proposed based on nonlinear excited-stateabsorption and working at non-resonant frequency. Experimental and theoretical results obtainedwith C_(60) and metal-organic materials using ns and ps laser at 532nm are presented.

Ultrafast Laser Energy Density and Retinal Absorption Cross-Section Determination by Saturable Absorption Measurements

Laser pulse nonlinear transmission measurements through saturable absorbers of known absorption parameters allow the measurement of their energy density. On the other hand, nonlinear transmission measurements of laser pulses of known energy density through absorbing media allow their absorption parameter determination. The peak energy density w0P of second harmonic pulses of a mode-locked titanium sapphire laser at wavelength λP = 400 nm is determined by nonlinear energy transmission measurement TE through the dye ADS084BE (1,4-bis(9-ethyl-3-car-bazovinylene)-2-methoxy-5-(2’-ethyl-hexyloxy)-benzene) in tetrahydrofuran. TE(w0P) calibration curves are calculated for laser pulse peak energy density reading w0P from measured pulse energy transmissions TE. The ground-state absorption cross-section σP and the excited-state absorption cross-section σex at λP, and the number density N0 of the retinal Schiff base isoform RetA in pH 7.4 buffer of the blue-light adapted recombinant rhodopsin fragment of the histidine kinase rhodopsin HKR1 from Chlamydomonas reinhardtii were determined by picosecond titanium sapphire second harmonic laser pulse energy transmission measurement TE through RetA as a function of laser input peak energy density w0P. The complete absorption cross-section spectrum

Excited-state nonlinear absorption and its description using density matrix theory

A density matrix theory with a ten-energy-level model in the molecular system irradiated bya pulsed laser at non-resonant wavelength is proposed. The reverse saturable absorption under ns and pspulses and the transformation from reverse saturable absorption to saturable absorption under strong ps pulses are described by this model. The correctness of the theoretical model is proved by experiments.

含无辐射过程四能级GSA/ESA上转换发光的理论分析(英文)

不同于通常的三能级GSA/ESA上转换系统,给出了一个包含无辐射弛豫过程的四能级上转换系统,利用速率方程模型,从理论上分析了其上转换动力学过程和发光特性.结果表明,体系上转换的上升过程由所包含能级的无辐射弛豫速率决定,而衰减过程主要由终态能级的弛豫速率决定.

激发态吸收(ESA)对掺铒光纤放大器的影响

本文分析了掺铒光纤放大器(EDFA)的激发态吸收(ESA)现象,得到了存在ESA时的EDFA增益与阈值的表达式。分析结果表明,ESA严重时将使EDFA不能正常工作。

Investigation of the Spin Crossover Complex [Fe(bapbpy)(NCS)_2 ] in Its Low-spin and Highspin State by DFT/TD-DFT/BS-DFT Calculations

The spin crossover（SCO） compound [Fe（bapbpy）（NCS）2],where bapbpy contains two fused N,N-bis（2-pyridyl）amines,has been studied by DFT/TD-DFT/BS-DFT methods.Several density functionals and basis sets were used in the calculation to obtain optimized geometries of the compound in the low-（LS） and high-spin（HS） states.The vibrational modes and IR spectra,spin splitting energies,excited states and UV/Vis absorption spectra were obtained.The structural parameters of the calculated isolated complex are in good agreement with the X-ray data.We investigate three dimers of [Fe（bapbpy）（NCS）2] complex for their magnetic properties.It has been found that the complex（1,3） has ferromagnetic character while the others are antiferromagnetic in nature by using a broken symmetry approach in the DFT framework（BS-DFT） with support from the coupling constant values（J） and spin density plots.

Green, orange, and red upconversion luminescence in Nd^(3+)/Yb^(3+): Cs_2NaGdCl_6 powders under 785 nm laser excitation

Nd^3＋：Cs2NaGdCl6 and Nd^3＋, Yb^3＋：Cs2NaGdCl6 polycrystalline powder samples were prepared by Morss method E. Under 785 nm semiconductor laser pumping, the upconversion luminescence of Nd^3＋ ions in Cs2NaGdCl6 was investigated at room temperature, and three upconversion emissions near 538 nm （Green）, 603 nm （Orange）, and 675 nm （Red） were observed and assigned to ^4G7/2→^4I9/2, （^4G7/2→^4I11/2; ^4G5/2→^4I9/2）, and （^4G7/2→^4I13/2; ^4G5/2→^4I11/2 ）, respectively. The dependences of these upconverted emissions on laser power and Nd^3＋ ion concentration were investigated, to explore the upconversion mechanism. The effect of doping Yb^3＋ ions on the upconversion luminescence of Nd^3＋ in Cs2NaGdCl6 was also studied under 785 nm laser excitation. The energy transfer processes were discussed as the possible mechanism for the above upconversion emissions.

H_(2)S第一吸收带振动激发态光解动力学的理论研究

本文利用切比雪夫实波包法研究了不同初始振动态下H_(2)S第一吸收带的光解量子动力学。由于初始振动态的波函数不同,计算得到的吸收光谱以及产物的振动态分布表现出不同的动力学特性,由于角坐标波函数的变化,初始伸缩振动激发态(1,0,0)和(0,0,1)的吸收光谱宽度和峰值与振动基态不同,而(0,1,0)振动态的吸收光谱中有两个几乎同样高的峰值.(0,1,0)态的产物振动态分布对激发能量的依赖不强,并由V=0的产物主导,但在(1,0,0)和(0,0,1)振动态的较低能量处占主导的产物是SH(X,V=1)碎片,产物的转动态分布对总能量的依讨赖性较弱,且分布非常冷并在j=1处达到峰值,但(0,1,0)振动态的转动态分布表现出明显的振荡,其各向异性参数随转动量子数的振荡行为不同于其他三种振动态的各向异性参数.

N,N-二甲基-6-丙酰-2-萘胺氢键复合物激发态超快动力学研究

抑制扭转分子内电荷转移(TICT)的形成能够显著增强发光材料的荧光强度和光稳定性,然而,目前缺乏准确预测TICT存在的方法。本文基于Kamlet-Taft理论,通过稳态/瞬态吸收光谱结合量化计算,对N,N-二甲基-6-丙酰-2-萘胺(PRODAN)在不同溶剂中的激发态动力学进行了研究。稳态光谱表明,PRODAN氢键复合物的斯托克斯红移主要依赖溶剂极性和供氢能力。瞬态吸收光谱表明,快时间τ_(1)和τ_(2)归属为分子内电荷转移和TICT形成过程,而慢时间τ_(3)和τ_(4)归属为溶剂化和荧光辐射过程。此外,结果表明极性和供氢能力的增大会加快PRODAN氢键复合物的动力学过程。计算表明,在较高极性且强供氢能力的甲醇溶剂中能形成稳定的TICT态。研究结果为荧光探针分子结构设计和溶剂选择提供了一定的指导意义。

Dual excited state deactivation pathways in TPZ2:A centrosymmetric dye with both high fluorescence and triplet state quantum yield

In this letter, excited state dynamics of TPZ2, a centrosymmetric PRODAN dye, has been studied by using several time-resolved spectroscopy techniques. Fluorescence quantum yield of TPZ2 is found to be 0.50 in both acetonitrile and ethanol solution. The radiative decay rate of the excited state of TPZ2 is determined to be 2.0×10^8 s^-1. Meanwhile, highly efficient triplet state and singlet oxygen generation have been observed in TPZ2 and the intersystem crossing（ISC） rate is determined to be 2.0×10^8s^-1. The almost identical ISC and non-radiative decay rates indicate that ISC is the only non-radiative decay pathway in TPZ2. Thus, dual excited state（S1） deactivation mechanism（50/50, fluorescence/ISC） of TPZ2 is proposed.Because of this unique property, TPZ2 has the potential to be used as biocompatible imaging and photodynamic therapy agent in the same time.

Excited State Properties of Fucoxanthin Aggregates

The structure and excited state properties of the H- and J-aggregates of the marine carbonyl carotenoid, fucoxanthin(Fx), were studied by various spectroscopic methods, and compared with those of Fx monomers in polar organic solvents. The fluorescent analysis indicated tliat the higher vibronic states of S2 contribute more to populating the S1 state, from which fluorescent emission mainly originates. Resonance Raman and density functional theory calculations confirmed the ‘card-packed' and chead-to-taiF structures of the H- and J-aggregates of Fx, respectively. An fs time-resolved absorption study proved the coexistence of Si and intramolecular charge transfer relaxation pathways upon excitation to the S2 state for both tlie monomers and aggregates.

980 nm LD激发下Yb^(3+),Er^(3+)∶Y_2O_3纳米晶粉体的上转换发光

用共沉淀法合成出Yb3+,Er3+离子双掺杂的Y2O3粉体,X射线衍射结果表明所制备粉体为立方Y2O3结构。场发射扫描电镜照片显示其颗粒形状为球形,粒径为60~80 nm;该粉体在波长为980 nm的半导体激光器激发下发射出中心波长为562 nm的绿色和660 nm的红色上转换荧光,分别对应于Er3+离子的4S3/2/2H11/2→4I15/2跃迁和4F9/2→4I15/2跃迁。发光强度和激发功率关系的研究揭示其均为双光子过程,能量传递和激发态吸收是上转换发光的主要机制。由于其高效的上转换发光性能,这种材料有可能应用于荧光标记和红外探测方面。

掺Er^(3+)硅酸盐玻璃上转换发光特性研究

研究了掺Er3+硅酸盐玻璃的吸收光谱和上转换光谱,应用Judd-Ofelt理论计算了Er3+强度参数Ωλ(λ=2、4、6)、跃迁振子强度、自发辐射几率、荧光分支比．上转换光谱分析表明:在522、545、658nm处有较强的绿光和红光,分别对应于3H11／2→4I15／2、4S3／2→4I15／2、4F9／2→4I15／2的跃迁,发光曲线拟合斜率分别为1．67,1．94,1．76;上转换发光机制主要是激发态吸收和能量转换,且均为双光子吸收过程．

Er^(3+),Yb^(3+)共掺杂SrTiO_3超细粉末的可见上转换发光

钛酸锶(SrTiO3)具有高介电常数、良好的绝缘性质、优良的物理化学稳定性和在可见光范围内的优异的透明度等优点,是一种重要的无机功能材料。近年来,Al3+,Ga3+等离子共掺杂的SrTiO3∶Pr3+做为一种优异的红色场发射显示(FED)荧光粉引起了人们的兴趣。另外,SrTiO3具有相对较小的声子频率,因而它可以作为一种有利于上转换发光的基质材料。以NaCl为助熔剂制备了Er3+,Yb3+共掺杂的SrTiO3超细粉末。在980nm激发下,样品发出很强的来自于Er3+离子的2H11/2→4I15/2,4S3/2→4I15/2(绿光)和4F9/2→4I15/2(红光)跃迁的上转换发光。Yb3+离子的共掺杂对Er3+离子的上转换发光起明显的增强作用。研究了上转换发光强度与稀土离子浓度以及激发光强度之间的依赖关系,表明在Er3+单掺杂和Er3+,Yb3+共掺杂的样品中,绿光和红光都是被双光子激发过程激发的。还对上转换发光的机理做了初步分析。