Frequency-resolving spatiotemporal wave-front sensor

We report on a high-resolution wave-front sensor that measures the complete spatial profile of any frequency component of a laser field containing multiple frequencies. This probe technique was developed to address the necessity of measuring the spatial overlap of the carrier field with each sideband component of the field exiting the output port of a gravitational-wave interferometer. We present the results of an experimental test of the probe, where we were able to construct the spatial profile of a single radio-frequency sideband at the level of -50 dBc.     

Amino Acid Chirality and Ferrocene Conformation Guided Self‐Assembly and Gelation of Ferrocene–Peptide Conjugates

The self‐assembly and gelation behavior of a series of mono‐ and disubstituted ferrocene (Fc)–peptide conjugates as a function of ferrocene conformation and amino acid chirality are described. The results reveal that ferrocene–peptide conjugates self‐assemble into organogels by controlling the conformation of the central ferrocene core, through inter‐ versus intramolecular hydrogen bonding in the attached peptide chain(s). The chirality controlled assembling studies showed that two monosubstituted Fc conjugates FcCO–L FL FL A‐OMe and FcCO–L FL FD A‐OMe form gels with nanofibrillar network structures, whereas the other two diastereomers FcCO–D FL FL A‐OMe and FcCO–L FD FL A‐OMe exclusively produced straight nanorods and non‐interconnected small fibers, respectively. This suggests the potential tuning of gelation behavior and nanoscale morphology by altering the chirality of constituted amino acids. The current study confirms the profound effect of diastereomerism and no influence of enantiomers on gelation. Correspondingly, the diastereomeric and enantiomeric Fc[CO‐FFA‐OMe]₂ were constructed for the study of chirality‐organized structures.     

Finite-well potential in the 3D nonlinear Schrödinger equation: application to Bose-Einstein condensation

Using variational and numerical solutions we show that stationary negative-energy localized (normalizable) bound states can appear in the three-dimensional nonlinear Schr?dinger equation with a finite square-well potential for a range of nonlinearity parameters. Below a critical attractive nonlinearity, the system becomes unstable and experiences collapse. Above a limiting repulsive nonlinearity, the system becomes highly repulsive and cannot be bound. The system also allows nonnormalizable states of infinite norm at positive energies in the continuum. The normalizable negative-energy bound states could be created in BECs and studied in the laboratory with present knowhow.     

Space-time contours to treat intense field-dressed molecular states. I. Theory

A molecular system exposed to an intense external field is considered. The strength of the field is measured by the number L of electronic states that become populated during this process. In the present article the authors discuss a rigorous way, based on the recently introduced space-time contours [R. Baer, et al., J. Chem. Phys. 119, 6998 (2003)], to form N coupled Schrodinger equations where N相似文献   

Selective photodissociation of O-H and O-D bonds from ground vibrational state of HOD using simple UV pulses

Selective cleaving of both O-H and O-D bonds in HOD is achieved using reasonably simple UV pulses to excite the HOD molecule in its ground vibrational state to the repulsive first excited A ((1)B(1)) surface. Detailed theoretical analysis of population transfer and flux in the H+O-DH-O+D channels reveals an important preparatory role for the cross-talk between the participating levels and a possible role for the beat structure of the population transfer oscillations in facilitating selective dissociation. Excitation using a 50 fs single color 67,169 cm(-1) laser pulse achieves a branching ratio H+O-DH-O+D=5.64 with 82% flux in the H+O-D channel and 15% in the H-O+D channel. A two color 50 fs laser pulse with frequencies of 54 920 and 52 303 cm(-1) provides a branching ratio of H-O+DH+O-D=2.83 and 52% flux in the H-O+D channel and 18% in the H+O-D channel.     

Femtosecond solvation dynamics in a neat ionic liquid and ionic liquid microemulsion: excitation wavelength dependence

Solvation dynamics in a neat ionic liquid, 1-pentyl-3-methyl-imidazolium tetra-flouroborate ([pmim][BF4]) and its microemulsion in Triton X-100 (TX-100)/benzene is studied using femtosecond up-conversion. In both the neat ionic liquid and the microemulsion, the solvation dynamics is found to depend on excitation wavelength (lambda(ex)). The lambda(ex) dependence is attributed to structural heterogeneity in neat ionic liquid (IL) and in IL microemulsion. In neat IL, the heterogeneity arises from clustering of the pentyl groups which are surrounded by a network of cation and anions. Such a nanostructural organization is predicted in many recent simulations and observed recently in an X-ray diffraction study. In an IL microemulsion, the surfactant (TX-100) molecules aggregate in form of a nonpolar peripheral shell around the polar pool of IL. The micro-environment in such an assembly varies drastically over a short distance. The dynamic solvent shift (and average solvation time) in neat IL as well as in IL microemulsions decreases markedly as lambda(ex) increases from 375 to 435 nm. In a [pmim][BF4]/water/TX-100/benzene quaternary microemulsion, the solvation dynamics is slower than that in a microemulsion without water. This is ascribed to the smaller size of the water containing microemulsion. The anisotropy decay in an IL microemulsion is found to be faster than that in neat IL.     

Applications of a local grid method for modeling chemical dynamics at a mean-field level

A local grid method proposed earlier is used to model chemical dynamical events in more than one dimension. Two different mean-field routes are applied to model problems representing dynamics of isomerization, H⁺-ion transfer, energy transfer, etc. The methods are seen to work with equal facility for both time-dependent and time-independent potentials. © 1996 John Wiley & Sons, Inc.     

Interactions of multiple spark-generated bubbles with phase differences

This paper aims to study the complex interaction between multiple bubbles, and to provide a summary and physical explanation of the phenomena observed during the interaction of two bubbles. High-speed photography is utilized to observe the experiments involving multiple spark-generated bubbles. Numerical simulations corresponding to the experiments are performed using the Boundary Element Method (BEM). The bubbles are typically between 3 and 5 mm in radius and are generated either in-phase (at the same time) or with phase differences. Complex phenomena are observed such as bubble splitting, and high-speed jetting inside a bubble caused by another collapsing bubble nearby (termed the ‘catapult’ effect). The two-bubble interactions are broadly classified in a graph according to two parameters: the relative inter-bubble distance and the phase difference (a new parameter introduced). The BEM simulations provide insight into the physics, such as bubble shape changes in detail, and jet velocities. Also presented in this paper are the experimental results of three bubble interactions. The interesting and complex observations of multiple bubble interaction are important for a better understanding of real life applications in medical ultrasonic treatment and ultrasonic cleaning. Many of the three bubble interactions can be explained by isolating bubble pairs and classifying their interaction according to the graph for the two bubble case. This graph can be a useful tool to predict the behavior of multiple bubble interactions.     

基于2,5-噻吩二甲酸的钙(Ⅱ)和钡(Ⅱ)配位聚合物的合成、晶体结构及性质

在溶剂热条件下,合成了2个碱土金属配位聚合物[Ca（tdc）（DMF）₂]_n（1）和[Ba（tdc）]_n（2）（H₂tdc=2,5-噻吩二甲酸）,分别用元素分析、红外光谱、X射线单晶衍射、粉末衍射、热重分析和荧光光谱对它们进行了表征。结构分析表明,配合物1具有4,4连接的二维层状结构,拓扑符号为（4⁴·6²）,而配合物2呈现三维网络结构。固体荧光测试表明配合物1比配合物2具有更显著的荧光性能。     

Nonlinear filters for chaotic oscillatory systems

This paper examines and contrasts the feasibility of joint state and parameter estimation of noise-driven chaotic systems using the extended Kalman filter (EKF), ensemble Kalman filter (EnKF), and particle filter (PF). In particular, we consider the chaotic vibration of a noisy Duffing oscillator perturbed by combined harmonic and random inputs ensuing a transition probability density function (pdf) of motion which displays strongly non-Gaussian features. This system offers computational simplicity while exhibiting a kaleidoscope of dynamical behavior with a slight change of input and system parameters. An extensive numerical study is undertaken to contrast the performance of various nonlinear filtering algorithms with respect to sparsity of observational data and strength of model and measurement noise. In general, the performance of EnKF is better than PF for smaller ensemble size, while for larger ensembles PF outperforms EnKF. For moderate measurement noise and frequent measurement data, EKF is able to correctly track the dynamics of the system. However, EKF performance is unsatisfactory in the presence of sparse observational data or strong measurement noise.