Longitudinal coherence length of an optical field

Longitudinal coherence of an optical field depending on the parameters of its frequency and angular spectra is considered. Expressions for the function and length of longitudinal coherence depending on the width of the frequency and angular spectra are obtained. The competitive influence of the angular and frequency spectra of the field on its longitudinal coherence is discussed. Experimental studies using a longitudinal shearing Michelson interferometer that proves theoretical results are performed.     

Autocorrelation low coherence interferometry

This paper describes the development of a new modality of optical low coherence interferometry (LCI) that is called autocorrelation LCI (ALCI). The ALCI system employs a Michelson interferometer to measure longitudinal autocorrelation properties of the sample optical field and does not require a reference beam. As the result, there is no restrictions applied on the distance between the sample and the ALCI system, moreover, this distance can even change during the measurements. We report experiments using a proof-of-principle ALCI system on a multilayer phantom consisting of three surfaces defining two regions of different refractive indices. The experimental data are in excellent agreement with the predictions of the theoretical model.     

EPR, 1H and 2H NMR, and reactivity studies of the iron-oxygen intermediates in bioinspired catalyst systems

Complexes [(BPMEN)Fe(II)(CH(3)CN)(2)](ClO(4))(2) (1, BPMEN = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-diaminoethane) and [(TPA)Fe(II)(CH(3)CN)(2)](ClO(4))(2) (2, TPA = tris(2-pyridylmethyl)amine) are among the best nonheme iron-based catalysts for bioinspired oxidation of hydrocarbons. Using EPR and (1)H and (2)H NMR spectroscopy, the iron-oxygen intermediates formed in the catalyst systems 1,2/H(2)O(2); 1,2/H(2)O(2)/CH(3)COOH; 1,2/CH(3)CO(3)H; 1,2/m-CPBA; 1,2/PhIO; 1,2/(t)BuOOH; and 1,2/(t)BuOOH/CH(3)COOH have been studied (m-CPBA is m-chloroperbenzoic acid). The following intermediates have been observed: [(L)Fe(III)(OOR)(S)](2+), [(L)Fe(IV)═O(S)](2+) (L = BPMEN or TPA, R = H or (t)Bu, S = CH(3)CN or H(2)O), and the iron-oxygen species 1c (L = BPMEN) and 2c (L = TPA). It has been shown that 1c and 2c directly react with cyclohexene to yield cyclohexene oxide, whereas [(L)Fe(IV)═O(S)](2+) react with cyclohexene to yield mainly products of allylic oxidation. [(L)Fe(III)(OOR)(S)](2+) are inert in this reaction. The analysis of EPR and reactivity data shows that only those catalyst systems which display EPR spectra of 1c and 2c are able to selectively epoxidize cyclohexene, thus bearing strong evidence in favor of the key role of 1c and 2c in selective epoxidation. 1c and 2c were tentatively assigned to the oxoiron(V) intermediates.     

Ozone resistance of crosslinked blends of butadiene-acrylonitrile and ethylene-propylene-diene elastomers and interphase interaction in these blends

The relation of ozone resistance to the volume and structure of the interphase layer and the amounts of crosslinks in the interlayer was studied for covulcanizates of butadiene-acrylonitrile rubbers of various polarities with ethylene-propylene-diene (EPDM) elastomers that differed in the comonomer composition and stereoregularity of propylene units. It was shown that the ozone resistance is determined by the compatibility of the components, the interlayer volume and density, the amount of crosslinks in the interlayer, and the strength of the EPDM network.     

Influence of the frequency spectrum width on the transverse coherence of optical field

Transverse spatial coherence of the optical field depending on parameters of angular and frequency spectra is considered. Expressions for the function and length of the transverse coherence in relation to the widths of the angular and frequency spectra are obtained. Experimental studies with a modified high-power Young interferometer that prove theoretical results are performed.     

Oxo complexes of high-valence iron in oxidation catalysis

This review deals with oxo complexes of high-valence iron (oxoferryl, or simply ferryl complexes), which play an important role in the selective oxidation of hydrocarbons and other organic compounds. The efficiency and high selectivity of natural oxygenases stimulates researchers to design chemical analogues of these systems. Since the advantages of biological and biomimetic oxidation are due to the participation of ferryl intermediates, we will consider the ways of obtaining relatively stable oxo complexes of high-valence iron and their geometric and electronic structure and reactivity.     

Effect of decoherence of optical field with broad angular spectrum upon propagation through transparent media interfaces

The effects of the decoherence of a narrow-band optical field with a broad angular spectrum upon propagation through a plate of a transparent medium placed in one of the arms of the Michelson interferometer are established.     

The influence of the numerical aperture of a beam probing an object on the determination of the thickness of a layered object in confocal microscopy

The influence of the numerical aperture of a light beam probing an object on the value measured with a confocal interference microscope when determining the thickness of layered object has been theoretically and experimentally investigated. The dependence of the measured value on the numerical aperture in the form of an analytical formula is obtained. It is established that the measured value is determined by the average longitudinal spatial frequency of the field probing the object. The results of experimental verification of the dependence obtained allow us to conclude that it is possible to increase the measurement accuracy of geometrical thickness and refractive index of layered micro-objects by the methods of confocal microscopy.

     

Manifestation of longitudinal correlations in scattered coherent fields in an interference experiment

The processes of formation of interference signals in the scattered coherent field with a wide angular spectrum in a scanning Michelson interferometer are considered. The effect of longitudinal correlation properties of the light-field complex amplitude on parameters of the interference oscillation envelope, upon detection of the signal in the image space and in the near-field region of diffraction, is studied.     

Erratum to: The Influence of the Numerical Aperture of a Beam Probing an Object on the Determination of the Thickness of a Layered Object in Confocal Microscopy

Optics and Spectroscopy - erratum