Intensity Correlation Spectroscopy Research Articles

Intensity–intensity correlations and low-frequency quantum beats in three-level systems

We theoretically investigate two-time intensity–intensity correlation spectroscopy in three-level atoms, a spectroscopic method that allows for direct detection of energy level structures and resonances in complex molecules. We show that in three-level Λ or V-systems, a richer spectroscopic signature is obtained when the applied fields are detuned from the transitions to values other than the typical zero-detuning or two-photon detuning settings. This allows us to identify, in the limit in which the overall decoherence rate from an excited state is much smaller than the Rabi frequency of the driving field, areas of parameter space for a three-level V-system in which low-frequency quantum beats can be generated while still maintaining significant signal amplitude. This may prove advantageous in improving the quality and ease of measurements in quantum beat spectroscopy as this type of experimental technique requires a high degree of time resolution.

Intensity correlation measurement system by picosecond single shot soft x-ray laser

We developed a new soft x-ray speckle intensity correlation spectroscopy system by use of a single shot high brilliant plasma soft x-ray laser. The plasma soft x-ray laser is characterized by several picoseconds in pulse width, more than 90% special coherence, and 10(11) soft x-ray photons within a single pulse. We developed a Michelson type delay pulse generator using a soft x-ray beam splitter to measure the intensity correlation of x-ray speckles from materials and succeeded in generating double coherent x-ray pulses with picosecond delay times. Moreover, we employed a high-speed soft x-ray streak camera for the picosecond time-resolved measurement of x-ray speckles caused by double coherent x-ray pulse illumination. We performed the x-ray speckle intensity correlation measurements for probing the relaxation phenomena of polarizations in polarization clusters in the paraelectric phase of the ferroelectric material BaTiO(3) near its Curie temperature and verified its performance.

Expansion of intensity correlation spectroscopy for lifetime measurements—application to intracellular oxygen dynamics measurements

We report on a simple correlation method for lifetime measurements using a random modulated excitation light source. We use an intensity correlation function of emission for lifetime analyses. In this method, no reference timing of the excitation is required. We apply the correlation method to measure phosphorescence decays and successfully demonstrate in the analysis of the phosphorescence decay from Pd(II) porphine in HeLa cells under aerobic and anaerobic conditions to understand the oxygen dynamics in individual cells. The method is applicable to faster decay time measurements down to a nanosecond range when the detection system is improved. Current fluorescence correlation setups can easily be modified for lifetime measurements, expanding the applicability in biological problems.

Coherence in X-ray physics.

Highly brilliant synchrotron radiation sources have opened up the possibility of using coherent X-rays in spectroscopy and imaging. Coherent X-rays are characterized by a large lateral coherence length. Speckle spectroscopy is extended to hard X-rays, improving the resolution to the nm range. It has become possible to image opaque objects in phase contrast with a sensitivity far superior to imaging in absorption contrast. All the currently available X-ray sources are chaotic sources. Their characterization in terms of coherence functions of the first and second order is introduced. The concept of coherence volume, defined in quantum optics terms, is generalized for scattering experiments. When the illuminated sample volume is smaller than the coherence volume, the individuality of the defect arrangement in a sample shows up as speckle in the scattered intensity. Otherwise, a configurational average washes out the speckle and only diffuse scattering and possibly Bragg reflections will survive. The loss of interference due to the finite detection time, to the finite detector pixel size and to uncontrolled degrees of freedom in the sample is discussed at length. A comparison between X-ray scattering, neutron scattering and mesoscopic electron transport is given. A few examples illustrate the possibilities of coherent X-rays for imaging and intensity correlation spectroscopy.

Correlation spectroscopy with excitation by noise light: excited-state signals in Rb atoms

An intensity correlation spectroscopy of the excited state with excitation by noise light is studied in Rb atoms. The shapes of Zeeman and hyperfine signals on the Fourier spectra, which are obtained from the cross-correlation between the excitation and emission intensities, are well explained by linear response theory.

Correlation spectroscopy with noise light excitation

Abstract Intensity correlation spectroscopy with noise light excitation is studied experimentally and theoretically. Zeeman signals of the ground state of the D 1 transition in Rb atoms were observed. The signals appear in the power and cross spectra obtained from the auto- and cross-correlations of the pump and probe intensities. The frequency resolution is determined by the inverse of the measuring time and is not limited by the spectral width of the light source. A high sensitivity was obtained in the experiment, and a high frequency resolution close to the theoretical limit was achieved. The signal shapes in the Fourier spectra are analyzed by using linear response theory, and the observed signal shapes can well be explained.

Atomic Transport in an Optical Lattice: An Investigation through Polarization-Selective Intensity Correlations.

We present an experimental investigation of the local dynamics and spatial diffusion of atoms in a rubidium optical lattice using polarization-selective intensity correlation spectroscopy in both the time and frequency domains. Autocorrelations of the circularly polarized components of the fluorescence light are shown to give access to the atomic dynamics in a single optical potential well. By contrast, cross correlations between opposite circular components of the scattered light provide information about atomic transport in the lattice through escape and recapture between neighbor potential wells.

Theoretical and experimental study on the profile of pump—probe time-resolved intensity correlation spectroscopy with incoherent light beams

An expression for the time profile of pump—probe two-photon intensity correlation spectroscopy with incoherent light beams is derived by using the perturbative density matrix method. Profiles of pump—probe time-resolved stimulated emission from a rhodamine 6G dye solution excited by incoherent light beams are measured. Origins of rising as well as decaying components of the profile are discussed by using the derived expression. Effects of the intensity correlation time on the time profile of vibronic states coherently excited by incoherent light beams are theoretically investigated.

Preparation of a diblock copoly (oxybutylene/ oxyethylene) and study of its micellisation and surface properties in dilute aqueous solution

A diblock copoly(oxybutylene/oxyethylene), B 33E 135, was prepared by sequential anionic copolymerisation and its micellar and surface properties in dilute aqueous solution were determined. The methods used were surface tension, gel-permeation chromatography (GPC), light scattering intensity and photon correlation spectroscopy (PCS). The quantities reported include the critical micelle concentration, the area per molecule at the air-water interface and the micellar diffusion coefficient and size. Good agreement was found between hydrodynamic radii determined by GPC and PCS.

Decorrelation of multiple scattering for an arbitrary scattering angle

Multiple scattering currently presents a major limitation for intensity correlation spectroscopy of quasi-elastically scattered light from concentrated colloidal systems. Theoretical treatments have been restricted to low orders of multiple scattering. Experimentally, suppression of multiple scattering by dual-beam cross-correlation setups has been restricted to a 90-deg fixed scattering angle. We propose a variable scattering angle cross-correlation scheme and present the results of a successful experiment on a highly concentrated aqueous suspension of polystyrene spheres.

Latex Article Size Analysis by the Coulter® Nano-sizer(suTM):Responce to Synthesis Mixtures of Sizes, Outzise Particle and Corporation with Other Methods

Many techniques have been developed to monitor the particle size distribution of latex and slurries, where the primary objective is to assure the uniformity and quality of the product. Unfortunately, most of the techniques which are adaptable to routine quality control, such as Beckman DU or Higher Order Tyndall Spectrum, do not have the ability to detect other important quality features such as outsize or flocculated particles in the system. Other methods such as disc centrifugation, are sensitive to outsize particles, but have other limitations. The newest method, intensity (or frequency) correlation spectroscopy, has been made commercially available in an instrument called the Coulter ® Nano-sizer. This instrument, at a cost of about $25,000.00, will give rapid (under 5 min) automatic and accurate values of the average size and polydispersity of a latex or slurry in the range from 40 to 3000 nm. It is the objective of this report to document the response of the method to various chemical types of latex, but also to latices containing outsize particles and two or more families of particles. The results of this study show that the Coulter ® Nano-sizer gives excellent particle size data correlations with other accepted methods, on lattices of narrow or broad distribution. Moreover, the method does display a sensitivity to outsize particle content, although this sensitivity varies with chemical type of latex.

Intensity Correlation Metrology: A Comparative Study

The statistical theory of fully developed, coherent speckle patterns is compared to classical coherence theory. It is shown that speckle correlations are directly analogous to the Hanbury Brown and Twiss effect. On that background a unified description is given for a number of measurement techniques based on intensity correlation measurements in scattered laser light: holographic interferometry, speckle pattern interferometry, speckle photography, stellar speckle interferometry, laser Doppler velocimetry and intensity correlation spectroscopy.

Poly(oxyethylene) chain scission following γ-irradiation of triton X-100 and other commercial non-ionic surfactants

γ-Irradiation of micellar solutions of non-ionic surfactants (e.g. Triton X-100, Triton X-405 and Cetomacrogol 1000) has been found to lead to poly(oxyethylene) chain scission rather than to poly(oxyethylene) chain cross-linking as has been found for poly(oxyethylene) of high molecular weight. Viscosity, surface tension, cloud point, solubilisation and nuclear magnetic resonance measurements, together with light scattering techniques (both total intensity and photon correlation spectroscopy) support the conclusion that poly(oxyethylene) chain scission occurs with the non-ionic surfactants investigated leading to the formation of mixed micelles.

Intensity correlation spectroscopy of the resonance fluorescence light of two-atomic molecules

The spectroscopic application of intensity correlation measurements of the resonance fluorescence light from two-atomic molecules is proposed. It is shown that from the intensity correlation function not only the natural line width of the electronic transition and the electron-vibration coupling strength but also very narrow homogeneous vibrational line widths can be determined without any use of a spectral apparatus.

Size determination of Streptococcus mutans 10499 by laser light scattering

We have performed three different optical experiments to determine the mean size of the bacterial strain Streptococcus mutans 10449, a microorganism with dimensions comparable to the wavelength of the light used in our experiments. The three optical measurements give size values which are consistent with one another and favorably comparable to the consistency we found in identical measurements on a test system of polystyrene spheres of dimensions similar to the bacteria. Homodyne time correlation and power spectrum spectroscopy both depend on the coherence and monochromaticity of laser light for the determination of the mean diffusion coefficient of the scatterers. The Stokes-Einstein equation then relates the diffusion constant to the cell size. Differential light scattering relies for the interpretation of experimental data on the classical theoretical analysis of the angular distribution of scattered light from a scattering object. The three methods yield mean values for the radius of S. mutans 10499 of 0.324 +/- 0.006 mum, 0.0325 +/- 0.007 mum, and 0.315 +/- 0.009 mum, respectively. However, since intensity correlation spectroscopy provides a direct measure of polydispersity, it would appear to be the preferred single measurement technique for size determination.

Application of intensity correlation spectroscopy to the measurement of continuous distributions of spherical particles

This paper extends the formalism whereby one can obtain the parameters describing specific size distributions of spherical particles from the cumulants, which are commonly measured in intensity correlation spectroscopy, to include the Pearson III, Pearson V, Schulz, and Schulz (molecular weight) number fractions of particle radii. We demonstrate explicitly that the reduced second cumulant K2/K21 has distinct upper bounds for each of the distributions. The range of scattering angles and distributional parameters for which the Rayleigh–Gans corrections (to second order in the scattering vector q) are negligible is specifically calculated. The method is applied to data from human serum very low density lipoproteins and from narrowly distributed polystyrene latex spheres.

Intensity-correlation study of the effect of dodecanol on sodium dodecyl sulfare aqueous solutions near the critical micelle concentration

Aqueous solutions of an ionic surfactant with the addition of a long-chain alcohol insoluble by itself in water are investigated by intensity-correlation spectroscopy. The anomalous enhancement of the turbidity of the solution in a narrow range of concentration close to the critical micelle concentration is found to be due to the formation of emulsion droplets having a radius of about 500 A. The sensitivity of the intensity-correlation technique to the presence of small amounts of water-insoluble material in the surfactant is shown to be very high.

Photon statistics of laser light scattered by motile spermatozoa

The intensity of laser light scattered by swimming spermatozoa is experimentally determined to obey a gaussian distribution. This is due to the fact that the fluctuations of the electric susceptabilities of the sperm system accord with gaussian statistics. The result is obtained from the light intensity correlation data and the photoelectron counting distribution with a photoelectron counting technique. It also gives us the justification of the usual process in light intensity correlation spectroscopy of swimming spermatozoa when we get the susceptibility correlation function from the experimentally obtainable intensity correlation function.

Measurement of a continuous distribution of spherical particles by intensity correlation spectroscopy: Analysis by cumulants

This paper presents the measurement and analysis of a continuous distribution of spherical particles by intensity correlation spectroscopy. The method of cumulants is used for the analysis. The first three cumulants are calculated and compared for Gaussian and rectangular distributions of particle sizes. The method is used to characterize a continuous distribution of polystyrene latex spheres (PSL). The results of these light scattering measurements are compared to electron microscope data for the same sample of PSL. The results agree with each other to within the experimental error.

Analysis of Macromolecular Polydispersity in Intensity Correlation Spectroscopy: The Method of Cumulants

The first order electric field correlation function of laser light scattered by polydisperse solutions of macromolecules can be written as a sum or distribution of exponentials, with decay rates proportional to the diffusion coefficients of the solute molecules. It is shown that the logarithm of this correlation function is formally equivalent to a cumulant generating function. A method is described by which the distribution function of the decay rates (and thus the extent of polydispersity) can be characterized, in a light scattering experiment, by calculation of the moments or cumulants. The systematic and random statistical errors in the calculated cumulants are discussed.