Measurement of the (14)N nuclear quadrupole resonance frequencies by the solid effect

(1)H-(14)N nuclear quadrupole double resonance using magnetic field cycling between high and low magnetic field and solid effect in the low magnetic field is analyzed in details. The transition probabilities per unit time for the solid-effect transitions are calculated. The double resonance spectra are calculated in the limiting cases of fast and slow nitrogen spin-lattice relaxation. The double resonance spectra are measured in histamine and quinolinic acid. The experimental spectra are analyzed and the (14)N NQR frequencies are determined.     

Sensitivity of nuclear-quadrupole double-resonance detection of half-integer spin nuclei

The sensitivity of the Slusher and Hahn’s nuclear quadrupole double resonance technique is calculated in general for an arbitrary nuclear spin S of the quadrupole nuclei and for an arbitrary asymmetry parameter η of the electric field gradient tensor. The nuclear spin S = 5/2 (¹⁷O, ²⁵Mg, …) is treated in details. The influence of the cross-relaxation rate between the quadrupole nuclei and the abundant spin system on the sensitivity of double resonance is discussed. The results of the theoretical analysis are applied in the analysis of the ¹H–¹⁷O nuclear quadrupole double resonance spectra in p-toluenesulfonamide and 2-nitrobenzoic acid. The 17O nuclear quadrupole resonance frequencies from a sulfonamide group are determined for the first time. The proton–oxygen cross-relaxation rates and the proton local frequency in zero external magnetic field are experimentally determined from the nuclear quadrupole double resonance spectra.     

FMR study of superparamagnetic Ni particles with weak and strong magnetic anisotropy

The method of ferromagnetic resonance (FMR) was used to study the process of thermal decomposition of the layered double hydroxides of lithium-aluminum and nickel-aluminum with intercalated EDTA complexes of nickel. The magnetic resonance spectra of nickel superparamagnetic nanoparticles were recorded at two temperatures (300 and 77 K). A computer simulation of FMR spectra was based on a modified statistic model which assumes the resonance of single-domain particles randomly oriented in an amorphous matrix. It is suggested that the line of the magnetic resonance of superparamagnetic particles narrows due to effects similar to those of dynamic narrowing in electron spin resonance and nuclear magnetic resonance spectra. In the framework of the model used, a fairly good agreement was achieved between calculated and experimental data. The formation of the two types of particles with strong (about 2·10⁶ erg/cm³) and weak (about 2·10⁵ erg/cm³) effective magnetic anisotropy was established.     

Resonance fluorescence spectrum of a three-level atom. II. Numerical results

Numerical computations are presented for the excitation spectra arising from the interaction between a three-level atom in the cascade configuration and a strong electromagnetic field whose frequency mode is initially populated. The excitation spectra are considered when the laser field is at resonance with the equally spaced levels of the atom as well as a function of the detunings. The physical process of optical amplification occurs without population inversion and it is more pronounced when the laser field is detuned than when it is at resonance. The shapes of the spectral lines for a number of side-bands are of the absorption-amplification type rather than that of the absorption one. In the presence of detunings as well as in the cooperative two-photon cascade process, the resulting spectra are far more complicated than those occuring at resonance. Results of numerical calculations for a wide range of Rabi frequencies and detunings are presented graphically.     

Proton spin relaxation in 2-chloroacrylontirile by double resonance

Nuclear magnetic double resonance experiments were performed on the strongly coupled two-proton system (AB) in 2-chloroacrylontirile to study the spin relaxation processes. The single resonance parameters of the AB spectrum are (operating frequency 100 MHz): |vA - vB|=9.85±0.1 Hz and J _AB=2.8±0.1 Hz. Frequency-sweep double resonance spectra were obtained by irradiating each of the four transitions at different strengths of irradiation in the range 0.015 Hz to 2.35 Hz. These spectra were analysed by using the ‘Bloch approximation’ in the rotating frame for the ‘high’ irradiation strengths and the ‘simple line’ approximation for the ‘low’ irradiation strengths. The analysis showed that the proton relaxation in this molecule can be described by interaction with isotropic random fields of nearly equal strengths at the two nuclei with no appreciable correlation between them. Internal dipole-dipole interaction is not a significant mechanism (at room temperature). It is shown that for analysing ‘low’ irradiation spectra the choice of certain functions of intensity changes would lead to a marked distinction between the different relaxation mechanisms.     

High-field pulsed EPR and ENDOR of Gd3+ complexes in glassy solutions

In this work D-band pulsed electron paramagnetic resonance was used to record the field-sweep spectra of several Gd³⁺ complexes in glassy water-methanol solutions. These spectra were analyzed by a specially developed stochastic superposition model that predicted the essential features of the distribution of the crystal field interaction (CFI) parameters in glassy systems. As a result of this analysis, the CFI distributions for the studied complexes were evaluated. The D-band Mims¹H electron-nuclear double resonance spectra were free from CFI-related distortions, which allowed us to accurately determine the hyperfine interaction (HFI) parameters for water ligand protons and to unequivocally establish that the HFI distribution is solely related to the distribution of the Gd?H distances.     

淡水养殖珍珠中有机物的激光共振拉曼光谱分析

采用3个不同的激发波长λ=514,633和785 nm对淡水养殖珍珠进行了较为系统的原位拉曼光谱研究,且与相同条件下测定的苹果蜗牛卵壳拉曼光谱进行对比,结果表明:(1)珍珠中所探测到的有机物拉曼峰频率色散明显,推测为聚乙炔类物质,而非前人所认为的类胡萝卜素;(2)苹果蜗牛卵壳中有机物为典型的类胡萝卜素,当λ变化时其拉曼峰基本无频率色散现象;(3)根据拉曼峰位置推测珍珠中聚乙炔类物质共轭C=C双键的数目约为10和16,蜗牛卵壳中类胡萝卜素的共轭C=C双键的数目约为13.     

Relaxation effects in weakly-coupled three spin systems by double resonance

Nuclear magnetic double-resonance spectra of weakly-coupled spin systems exhibit several interesting features. The effect of relaxation on the symmetry properties of double resonance spectra of weakly-coupled spin systems is investigated using spin inversion operators. The double-resonance spectra of the AX₂ type systems formed by the protons in (I) 1,1,2-trichloroethane and in (II) 2,2-dichloroethanol (excluding the hydroxyl proton) exhibit these symmetry effects. In both these molecules relaxation is contributed by several mechanisms. In sample II the effect of the exchanging proton in the hydroxyl group is also considered and the exchange time is estimated.     

Research on double resonance peaks and abnormal frequency shift in permeability spectra of annealed FeCoB films

A FeCoB magnetic film was prepared by a magnetron sputtering method and then was divided into several small pieces for vacuum annealing at different temperatures. The dependence of the coercivity along the hard axis on the annealing temperature reveals a degeneration of softness with the growth of grain size when the annealing temperature is above 350 °C. In permeability spectra measurements, double resonance peaks and an abnormal positive shift in the resonance peak at higher frequency with the increase in annealing temperature are observed. The existence of two peaks is attributed to the double magnetic phases (Fe and FeCo) in the films. The positive shift in the resonance peak at higher frequency has been analyzed and ascribed to the enhanced internal stray fields with the annealing temperature. This phenomenon of positive frequency-shift is very fascinating and novel, which makes the ferromagnetic films more efficient for the applications in the noise absorbing area.     

Optical double resonance spectra under finite bandwidth excitations

A formalism based on the theory of multiplicative stochastic processes is presented to treat the effects of finite band- with excitations on the optical double resonance spectra. Numerical results for the fluorescent spectra and the second-order intensity correlation functions are presented and discussed.     

Transmission spectra through photonic double quantum well system

By means of the modal expansion method with an R-matrix propagation algorithm, effects of the coupling between resonance photonic states on the resonance tunneling through a double quantum well structure are investigated. We examine the effects on the transmission spectra due to variation of the second well width and middle barrier thickness. Drastic change of the tunneling spectra is found and analyzed when the wells are filled with left-hand media.     

Infrared-microwave double resonance of propynal by using the 3.51 μm HeXe laser

The 3.51 μm HeXe laser is magnetically tuned over a wavenumber of 0.2 cm^?1 and used for infrared absorption and double resonance spectroscopy. Eight rotation-vibration lines of propynal in the ν₂ band are assigned by the Stark effect. Eleven microwave transitions in the v₂ = 1 vibrational state are observed by the method of infrared-microwave double resonance. The rotational constants of the excited state and the band origin of the vibration ν₂ are determined from the observed spectra.     

共振拉曼效应和电子-声子耦合对线性多烯分子共振拉曼光谱的影响

线性多烯分子具有高强度且信息丰富的共振拉曼光谱,在生物学、光电材料和医学等方面都有一定应用.而含有共轭双键的短链β胡萝卜素分子是多烯分子中极具有代表性的分子.在激发光作用下π电子与CC键振动相互作用影响着吸收光谱和拉曼光谱,而共振拉曼效应和电子-声子耦合影响着共振拉曼光谱的强度、频率和线型.测量了β胡罗卜素分子在二氯乙...     

The Mo−OH proton of the low-pH form of sulfite oxidase: Comparison of the hyperfine interactions obtained from pulsed ENDOR, CW-EPR and ESEEM measurements

Pulsed electron nuclear double resonance (ENDOR) spectra have been obtained for the exchangeable Mo-OH proton of the low-pH form of native chicken liver sulfite oxidase (SO) and recombinant human SO for the first time. The spectra of the two enzymes are very similar, indicating a similar binding geometry of the hydroxyl ligand to the Mo center. The isotropic hyperfine interaction (hfi) constant for the proton of the OH ligand in both enzymes is about 26 MHz. The anisotropic components of the hfi obtained from the pulsed ENDOR spectra are about 1.6–1.8 times larger than those obtained by continuous-wave electron paramagnetic resonance and electron spin echo envelope modulation. These hfi differences are explained by a rotational disorder of the Mo-OH group. A similar rotational disorder of the coordinated exchangeable ligand has been found previously for the high-pH and phosphate-inhibited forms of SO.     

Direct extraction of large quality factors and resonant frequencies from Padé interpolated resonance spectra

Extracting the quality factor and resonant frequency of photonic crystal resonators simulated using the finite-difference time-domain algorithm is investigated. The Padé interpolation method is applied to the resonance spectra, and closed form expressions for the quality factor and center frequency in terms of the coefficients in the Padé function are presented. The method is applied to simulations of the photonic crystal double heterostructure cavity.     

Formation of two pions on nuclei in A(γ, ππN)B reactions

A model is proposed for double pion photoproduction on nuclei that is accompanied by nucleon emission. Simple models that faithfully reproduce single-particle differential cross sections are used to describe photon interactions with intranuclear nucleons. The calculated cross sections for pion photoproduction on ¹²C nuclei are compared with inclusive pion spectra measured in the second resonance region of photon energies.     

Determination of bromine and iodine in powder samples by spectra in the vacuum region

Methods for the introduction of nonconducting powder samples containing halogens into the corona of a low-voltage pulsed discharge in a vacuum are considered. It is shown that the spectra of the halogens can be obtained by using double layer pellets. Using the resonance lines in the spark spectra of bromine and iodine in the analysis enabled one to determine contents of down to 0.5 microgram which in combination with a preliminary enrichment corresponds to a relative sensitivity of 5 · 10^–5%.     

Symmetrie und Mikrowellenspektren mehratomiger paramagnetischer Zentren

The relation between the symmetry of an arbitrary polyatomic paramagnetic center and the spin-Hamiltonian ofAbragam andPryce is examined. A new method permitting the construction of the spin-Hamiltonian from symmetry considerations without knowledge of the accurate wavefunctions is described. The procedure is very similar to the method of symmetry coordinates as used in the theory of molecular vibrations and brings to light results hitherto unknown. By this procedure we prove the existence of asymmetricg-tensors for paramagnetic centers of triclinic or monoclinic symmetry. The asymmetry of certain hyperfine-structure tensors found byMcConnell is confirmed. The method is applied to electron paramagnetic resonance (epr) spectra and the electron nuclear double resonance (ENDOR) spectra of colour centers, metallo-organic complexes and paramagnetic centers subjected to strong electric fields.     

联苯甲酸类化合物的高分辨核磁共振氢谱

本文报道十一种联苯甲酸类化合物的核磁共振氢谱,其中八种是由超导核磁共振仪作的。超导核磁共振氢谱使环上质子间的多重偶合所形成的复杂裂分简并,图谱简化。有利于联苯环系质子化学位移的解析。结合使用"双照射"记谱,对环上每一质子的归属都能作出合理的解释。但80兆核磁共振氢谱无法作到。本文所报道的十一种联苯甲酸的核磁共振氢谱均未见文献报道。