Field correlation effects on the resonant light scattering

Effects of incident photon field coherence on resonant light scattering have been investigated. In order to obtain the scattering intensity and the photon counting rate, an expression for the reduced density matrix for the scattered field has been derived. The expression involves the first-order correlation function of the incident field. The relation between the line shape of the scattered light and the bandwidth of the incident field has been clarified. Model calculations of the photon counting rate have been performed in the case of an incident field without first-order coherence. In our treatment, the transverse and longitudinal relaxation constants have been taken into account by using the impact approximation.     

Theory of correlation measurements of resonance light scattering

The boson nature of radiation is shown to give rise to a purely quantum mechanical exchange contribution to the intensity-intensity correlation function for resonant light scattering by an atomic or molecular system. The exchange contribution can be decomposed into three components, one involving the intensity correlation for a pair of coherently scattered photons (“resonant Raman” processes), another for a pair of incoherently scattered ones (“resonance fluorescence”), and the last involving the exchange correlation one of each. The intensity correlation measurements of Kimble et al., on optically pumped atomic beams of sodium atoms are interpreted with the theory, producing values of the decay rate of the excited sodium atoms and of the coherence time of the exciting radiation in good agreement with expectations.     

The absolute intensity of depolarised light scattering from liquid argon

The depolarised light scattering intensity from liquid argon has been measured relative to the 991 cm^?1 Raman line of benzene, whose absolute intensity is known. The mean-square induced polarisability anisotropy is (10.6±1.0) × 10^?51 cm⁶, approximately five times larger than previously reported, but in agreement with simulations based on the dipole-induced-dipole model and with another recent measurement.     

One-particle correlation function in evanescent wave dynamic light scattering

In order to interpret measured intensity autocorrelation functions obtained in evanescent wave scattering, their initial decay rates have been analyzed recently [P. Holmqvist, J. K. G. Dhont, and P. R. Lang, Phys. Rev. E 74, 021402 (2006); B. Cichocki, E. Wajnryb, J. Blawzdziewicz, J. K. G. Dhont, and P. R. Lang, J. Chem. Phys. 132, 074704 (2010); J. W. Swan and J. F. Brady, ibid. 135, 014701 (2011)]. A theoretical analysis of the longer time dependence of evanescent wave autocorrelation functions, beyond the initial decay, is still lacking. In this paper we present such an analysis for very dilute suspensions of spherical colloids. We present simulation results, a comparison to cumulant expansions, and experiments. An efficient simulation method is developed which takes advantage of the particular mathematical structure of the time-evolution equation of the probability density function of the position coordinate of the colloidal sphere. The computer simulation results are compared with analytic, first and second order cumulant expansions. The only available analytical result for the full time dependence of evanescent wave autocorrelation functions [K. H. Lan, N. Ostrowsky, and D. Sornette, Phys. Rev. Lett. 57, 17 (1986)], that neglects hydrodynamic interactions between the colloidal spheres and the wall, is shown to be quite inaccurate. Experimental results are presented and compared to the simulations and cumulant expansions.     

A lattice theory of light scattering from disordered spherulites

A lattice theory of orientational disorder in two-dimensional spherulites is developed in which the orientation direction of the optic axis in lattice cells is allowed statistically to deviate from its mean value in a manner correlated with the orientation in neighboring cells. The H_v light scattering patterns arising from such disordered spherulites deviate from the patterns for perfect spherulites in that there is excess intensity at both small and large scattering angles and the intensity at the maximum is lower. A comparison of the calculated scattering angular dependence with that which is experimentally measured permits assignment of values of correlation parameters. A consequence of this disorder is that the spherulite birefringence is reduced below that calculated on the basis of perfect crystalline orientation in agreement with experiment.     

Non-perturbative theory of four-wave light scattering in strong fields

Nonlinear four-wave light scattering (FWLS) on a three-level system is analyzed, adopting the density operator approach. A strong field Ω₁ is mixed by the material system with two fields Ω₂ and Ω₃ to yield an output field peaked at the frequency Ω₄ = Ω₁ + Ω₃ - Ω₂. The theory is developed within the dipole and Markov approximations. The strong resonant field is treated “exactly”, while the other fields are regarded as perturbations. The generated intensity is obtained as the expectation value of the photon number operator, estimated at the sixth order in the weak-field expansion. The generation of a coherent field at the frequency Ω₄ is due to processes where either a single molecule or a couple of molecules are involved. The total intensity is interpreted as the superposition of four contributions: a four-photon scattering process (FPS), a three-photon process (TPS), and two more processes related to resonance Raman scattering (RRS) and resonance fluorescence (RF). The method allows the deduction of nonlinearities in the generated intensity which are not included in fully perturbative treatment, and which, in the strong-field limit, originate the Rabi intensity dip of the lines.     

Characterization of gold nanoparticle bioconjugation by resonance light scattering correlation spectroscopy

<正>Gold nanoparticles(GNPs) have been widely used as probes and nanomaterials in certain biological and biomedical fields thanks to its special physical and chemical properties.However,it is still difficult to characterize GNPs-bioconjugates in solution,which has greatly limited further bioapplications of GNPs.In this study,we reported a single particle method for characterizing GNPsbiomolecules in solution using resonance light scattering correlation spectroscopy(RLSCS).The interaction of GNPs with bovine serum albumin(BSA) and thiol-modified oligonucletides were investigated.     

Measurement of the correlation radius in oil-in-water microemulsions by dynamic light scattering

The diffusion coefficient and correlation radius associated with the droplet particles in oil-in-water microemulsions (CTAB, octane, butanol, NaBr and water) were determined by dynamic light scattering- Unlike the case of CTAB micelles, there is a maximum in the correlation radius versus temperature plot.     

Influence of the potential on the intensity of depolarized light scattering ; in dense liquid argon

The depolarized light scattering intensity of argon at the triple point is calculated by molecular dynamics using the two-body Bobetic-Barker potential. The result differs from that obtained with a Lennard-Jones potential by no more than 15%.     

Effect of interference between anisotropic scattering entities on light scattering from polymer films. II. The correlation function approach

A theory is developed by use of the correlation function approach for calculating both the H_v and V_v intensity of scattered light for a concentrated assembly of spherulities. The scattering becomes a function of the radial and tangential polarizabilities of the spherulite α_r and α_t, the polarizability α_m of the medium, surrounding the spherulites, and the volume fraction ?_s of spherulites. The “effective polarizability of the surroundings” α_s, which appeared in previous theories, becomes function of these variables. The theory can explain, for example, why the V_v scattered intensity passes through a maximum during the course of crystallization.     

Low angle laser light scattering and photon correlation spectroscopy in surfactant vesicles

Using low angle laser light scattering, weight averaged molecular weights, M?_w, diffusion coefficients, and hydrodynamic radii, R_H, have been determined for completely synthetic surfactant vesicles, prepared by ultrasonic irradiation of dioctadecyldimethylammonium chloride. DODAC, and dihexadecylphosphate. DHP dispersion. Both the M?_w and R_H values were found to decrease exponentially as a function of sonication time. At the limit, M?_w and R_H for DODAC vesicles are 12.6 × 10⁶ dalton and 396 Å, and those for DHP vesicles are 23 × 10⁶ dalton and 595 Å. Calculations indicate both vesicles to be prolates.     

General theory of vibrational mode mixing and frequency shifts in resonance raman scattering

A general formalism is given for treating vibrational mode mixing, frequency shifts, and atomic equilibrium position shifts under electronic excitation in resonance Raman scattering. The theory is exact for first-order scattering at T = 0 K for all linear and quadratic electron-phonon coupling strengths. Numerical results illustrating mode mixing are presented.     

Effect of birefringence on the scattering of light

The effect of birefringence on light scattering is considered, using classical theory. It is shown that in conjunction with polarized light scattering, the use of birefringence can aid in the reduction of experimental errors; also how new checks on theory can be made. The treatment is applied to scattering from simple gaseous molecules and thin polymeric films.     

The three-body correlation spectral moments in depolarized interaction-induced light scattering of H2 at 297 K

The three-body correlation spectral moments of depolarized interaction-induced light scattering have been measured in normal H₂ at 297 K by means of an analysis of the density behaviour of the spectra between 10 and 300 cm⁻¹. Comparison with classical calculation shows a major discrepancy for the second moment which is attributed to the anisotropic properties of the interacting molecules.     

钍试剂Ⅱ与蛋白质作用的共振光散射特征及微量蛋白质的光散射测定

研究了钍试剂Ⅱ与蛋白质在pH 4 3条件下作用的共振光散射特征 ,并以此建立了测定微量蛋白质的新方法。用普通荧光分光光度计测量了这一体系的共振光散射光谱 ,考察了影响因素。在最佳实验条件下 ,牛血清白蛋白 (BSA)浓度在 0mg/L～ 1 0 0mg/L范围内成线性关系。方法已用于尿中微量蛋白质的测定     

On the time evolution of light scattering intensity from binary liquids quenched near and above the critical point

A method is presented for calculating the time evolution and the angular distribution or the intensity intensity scattered by a system which is quenched rapidly above and near its critical point. If the system is quenched exactly to the critical temperature, the two-point, equal-time correlation function has a universal scaling form, as a function of time and wave- number