Derivation of absorption coefficients from reflection spectra for dyed wool cloth

The Girin-Stephanov theory is used. The reflection coefficient for an elementary layer is derived from Fresnel's formula for normal incidence, as modified by a factor for the proportion of the area taken up by fibers.     

Acoustic scattering in dispersions: improvements in the calculation of single particle scattering coefficients

Measurements of ultrasound speed and attenuation can be related to the properties of dispersed systems by applying a scattering model. Rayleigh's method for scattering of sound by a spherical object, and its subsequent developments to include viscous, thermal, and other effects (known as the ECAH model) has been widely adopted. The ECAH method has difficulties, including numerical ill-conditioning, calculation of Bessel functions at large arguments, and inclusion of thermal effects in all cases. The present work develops techniques for improving the ECAH calculations to allow its use in instrumentation. It is shown that thermal terms can be neglected in some boundary equations up to approximately 100 GHz in water, and several simplified solutions result. An analytical solution for the zero-order coefficient is presented, with separate nonthermal and thermal parts, allowing estimation of the thermal contribution. Higher orders have been simplified by estimating the small shear contribution as the inertial limit is approached. The condition of the matrix solutions have been greatly improved by these techniques and by including appropriate scaling factors. A method is presented for calculating the required Bessel functions when the argument is large (high frequency or large particle size). The required number of partial wave orders is also considered.     

Optical absorption and scattering spectra of pathological stomach tissues

Diffuse reflection spectra of biotissues in vivo and transmission and reflection coefficients for biotissues in vitro are measured over 300–800 nm. These data are used to determine the spectral absorption and scattering indices and the scattering anisotropy factor for stomach mucous membranes under normal and various pathological conditions (chronic atrophic and ulcerous defects, malignant neoplasms). The most importan tphysiological (hemodynamic and oxygenation levels) and structural-morphological (scatterer size and density) parameters are also determined. The results of a morphofunctional study correlate well with the optical properties and are consistent with data from a histomorphological analysis of the corresponding tissues.     

Optical constants of single crystal of thiourea in the paraelectric and ferroelectric phases from infrared reflectance spectra

Infrared reflectance spectra at nearly normal incidence, parallel to the three crystallographic axes, were obtained at room temperature (Phase V) and at T = 85°K (Phase I). The dispersion parameters and the optical constants were calculated from the Kramers-Kronig relation. The results are in good agreement with previous studies of infrared absorption and Raman scattering.The optical data are interpretible in terms of C_2v molecular symmetry, but that a slight distortion to C_s, resulting in spectral modifications too small to be observed, is also possible.     

Determination of the kinetic coefficients of a gas in a supersonic jet from Brillouin spontaneous scattering spectra

The mean free path and the shear viscosity of molecular nitrogen are determined in a rarefied supersonic jet using the Brillouin spontaneous scattering technique. By examples of sub-and supersonic jets, the measured kinetic coefficients are shown to agree with the tabulated values of these parameters. These results are obtained using laser radiation, whose output power, which restricts the signal-to-noise ratio, is as low as 50 mW.     

Recording of absorption spectra for single cells in leaves

Models are used to obtain the spectra. The refractive index and absorption coefficient are presented for a single cell ofMorus nigra, as well as some parameters of the scattering indicatrix.     

Comparison of the sensitivities of IR absorption and raman scattering spectra to hydrogen bonding in methanol

The sensitivity of infrared (IR) absorption and Raman scattering (RS) spectra to hydrogen bonding in methanol is quantified by a comparative sensitivity factor, which can be expressed as the K = (I _b /I _ub )_IR/(I _b /I _ub )_RS, where the indices b and ub refer to H-bonded and unbound (free) OH groups, respectively. The resulting value for methanol, K ～ 20, is identical to that found previously for n-butanol, although the methods of measuring the degree of hydrogen bonding for these two alcohols were quite different. It is shown that, in some cases, Raman spectra can be converted to IR absorption spectra and vice versa. It is important for understanding differences in the shapes of OH stretching vibration bands in IR absorption and Raman spectra.     

An approximate analytic solution of the steady state Brillouin scattering in single mode optical fiber without neglecting the attenuation coefficient

The analysis of steady state Brillouin scattering in a long single mode optical fiber is presented. Meanwhile, an approximate analytical functions of distributed Brillouin scattering and pump wave along the fiber with the fiber attenuation coefficient are obtained for the first time. A comparison is made among the analytical solutions with the attenuation coefficient, the analytical solutions without the attenuation coefficient and the exact numerical solutions. The results show that the analytical solutions with fiber attenuation coefficient are more close to the numerical solutions, which can be used to describe the power distribution of the pump wave and the Stokes wave along the long distance single mode optical fiber accurately.     

A polarization method for measuring absorption spectra of single molecules

A new method for measuring low-temperature absorption spectra of single impurity molecules using a laser confocal polarized-light transmission microscope is proposed. The sensitivity of this method is of the same order of magnitude as that of fluorescence excitation spectroscopy. Combined use of both methods makes it possible to study distributions of impurity molecules by the magnitude of fluorescence quantum yield and their correlations with the linewidth distributions, as well as to determine if spectral jumps lead to changes in the fluorescence quantum yield.     

Structural properties of aqueous electrolyte solutions from i.r. absorption spectra

Summary Results are reported on near-i.r. absorption spectra of H₂O in the presence of a variety of electrolytes, in the temperature range of liquid state. Spectra are analysed by using a deconvolution method, presented and discussed in previous works, thus obtaining a new level of detail and completeness of information. This allows for the first time the separation of solute perturbation on the solvent structure in terms of electric-field effects (common to all solutes), steric effects (mainly determined by the ionic radius) and more subtle effects due to the electronic structure of the specific ion. The quantitative set of spectroscopical parameters obtained for the different solutions in the whole explored temperature range offers a potentially useful ground for comparison with results of computer simulation.

---

Riassunto In questo lavoro sono riportati risultati sugli spettri di assorbimento di H₂O nel vicino infrarosso in presenza di una varietà di elettroliti, nell'intervallo di temperatura dello stato liquido. Gli spettri sono analizzati usando un metodo di deconvoluzione, presentato e discusso in precedenti lavori, ottenendone un nuovo grado di risoluzione e completezza d'informazione. Questo ha permesso per la prima volta la separazione della perturbazione indotta dai soluti sulla struttura del solvente in termini di effetti di campo elettrico (comune a tutti gli ioni), effetti sterici (in media dipendenti dai raggi ionici) ed effetti piú fini dovuti alla struttura elettronica dei singoli ioni. Il quadro quantitativo dei parametri spettroscopici ottenuti per le differenti soluzioni nell'intervallo di temperature esplorato offre una base potenzialmente utile per un confronto con i risultati di simulazione al computer.

---

Резюме Приводятся результаты для слектров инфракрасного поглошения H₂O в присутствии различных электролитов в области температуп жидкого состояния. Полученные спектры анализируются, используя метод ?развертывания?, предложенный в предыдуших работах с целью получения нового уровня полноты информации. Этот подход впервые позволил разделить возмушение, обусловленное растворенным вешеством на структуру растворителя, на эффекты электрического поля (обшие для всех растворенных вешеств), на сферические эффекты (зависяшие от радиуса иона) и на более тонкие эффекты, обусловленные электронной структурой отдельного иона. Количественная система спектроскопических параметров, полученных для различных растворов во всей исследованной области температур, представляет потенциально полезную основу для сравнения с результатами машинного моделирования.

     

Frequency locking to the center of a 532 nm iodine absorption line by using stimulated brillouin scattering from a single-mode fiber

A simple method for frequency locking a frequency-doubled Nd:YAG laser to the center of line 1109 of the iodine absorption spectrum is described. The 31.6 GHz frequency shift provided by stimulated-Brillouin scattering from a single-mode silica fiber provides a probe signal that lies on the edge of line 1105 of the iodine spectrum. We adjust the frequency of the laser to maintain the transmission of a 5 cm iodine absorption cell at a value that places the unshifted laser line in the center of line 1109.     

Diffuse contribution to specular spectra and the specular contribution to diffuse spectra in X-ray scattering from rough interfaces

The angular dependences of the intensity of X-ray radiation scattered from multilayer systems with nonideal interfaces are investigated with due regard for the real geometry of a receiver. The influence of the interface roughness and the longitudinal and transverse correlations of the interface roughnesses on the specular- and diffuse-scattering spectra is analyzed. It is demonstrated that the inclusion of the diffuse contribution to the specular-scattering spectra provides information on the correlation lengths in the plane and in the direction perpendicular to the plane of the interface. The roughness parameters determine the ratio between the heights of the central Bragg peak and the diffuse plateau in the diffuse-scattering spectra. The spectra measured for several widths of the detector slit make it possible to separate the true specular and diffuse contributions. This allows one to interpret experimental data more accurately. The results of the calculations are illustrated by analyzing experimental scattering spectra for multilayer systems.     

The influence of absorption factors on the sensitivity of a virtual room’s sound field to scattering coefficients

Currently there is limited information on what scattering coefficients (SCs) to assign materials in geometrical room acoustic computer models. As a result, room modelers rely on general guidelines and intuition when assigning SCs. How sensitive is the predicted sound field to the user’s choice of scattering coefficients? The sound field’s sensitivity depends on its diffusivity (without SCs); the more diffuse the room’s sound field is, the less sensitive the virtual room is to the selection of SCs. In rooms with no fittings to diffuse sound energy, the sound field diffusivity is influenced by (1) room shape, (2) volume, (3) amount and (4) location of absorption, and (5) the choice of SCs. This investigation focuses only on the latter three factors. A rectangular room is modeled in ODEON v6.5 with 10 absorption schemes. These schemes vary in terms of the area of mirrored reflective surfaces, average absorption coefficient, and standard deviation of absorption. The amount of diffuse reflections at each room boundary as dictated by the SC is increased uniformly in each room. Changes in the room sound field, in particular in the reverberation time (T30), are examined at each step. Sound field diffusivity, and consequently a virtual room model’s sensitivity to SCs, is found to depend most on the area of mirrored reflective surfaces. Also, a proposed quantity called the Scattering Sensitivity Index appears to predict sound field diffusivity.