Quantum-mechanical calculation of the intensity distribution in resonance Raman spectra of guanine-cytosine pair

The method of quantum-mechanical calculation of the relative line intensities in the resonance Raman (RR) spectra of polyatomic molecules, which was previously applied to the analysis of the spectra of individual cyclic molecules and makes it possible to take into account the Herzberg-Teller and Duschinsky effects, as well as the frequency effect, is applied for the first time to the calculation of the spectra of a pair guanine-cytosine. Satisfactory agreement between the calculated results and the available experimental data is obtained. The particular features of the intensity distribution in the RR spectra of the guanine-cytosine pair excited by laser radiation at 266, 240, 218, and 200 nm are analyzed. The RR spectra of the guanine-cytosine pair are compared with the spectra of the individual guanine and cytosine molecules excited by the laser radiation at the same wavelengths.     

Quantum-mechanical calculation of the intensity distribution in resonance Raman spectra of thiosubstituted derivatives of uracil

A quantum-mechanical calculation of the intensity distribution in the resonance Raman (RR) spectra of 2-thiouracil and 4-thiouracil is carried out for exciting laser radiation at 300, 257, and 248 nm. It is shown that, for satisfactory agreement between the calculated results and the experimental data, it is necessary to take into account in the calculations of the relative intensities of lines the Herzberg-Teller effect and the contribution from excited electronic states adjacent to the resonance state. The general and specific features of the intensity distribution in the RR spectra of uracil and its thiosubstituted derivatives are compared and discussed.     

Quantum mechanical analysis of resonance Raman spectra of thymine

A direct quantum mechanical calculation of the relative intensities of lines in resonance Raman (RR) spectra of thymine was performed. The method of calculation is based on the adiabatic model in the Herzberg-Teller approximation. It is shown that the basic features of the intensity distribution in the spectra can be explained only by taking into account the vibronic mixing of electronic states and the contribution to the components of the scattering tensor from excited electronic states located close to the resonance state. The calculated results agree satisfactorily with experimental RR spectra of thymine excited by laser radiation at 266, 240, 218, and 200 nm. A comparative analysis of the intensity distribution in the RR spectra of thymine and uracil is carried out.     

Modulation of optical pulses under electromagnetically induced transparency conditions: transfer of the Rabi oscillations manifestation from the radiofrequency to the optical range

The relative intensities of lines in resonance Raman scattering spectra of isolated skatole and skatole-water complex have been calculated quantum mechanically. The influence of the intermolecular interaction on these spectra has been considered. Particular features of the intensity distribution in the resonance Raman scattering spectra of indole and skatole have been compared.     

Quantum-mechanical analysis of resonance Raman scattering spectra of the uracil molecule

A direct quantum-mechanical calculation of the relative intensities of lines in the resonance Raman scattering (RRS) spectra of uracil is performed by a method developed earlier by the authors on the basis of the adiabatic model in the Herzberg-Teller approximation [1]. It is shown that the main regularities in the intensity distribution of spectra can be explained only by taking into account the vibronic mixing of electronic states and the contribution to the scattering tensor components from the excited electronic states adjacent to the resonance state. The calculated results are in satisfactory agreement with the results of experimental studies of the RRS spectra of uracil excited by laser radiation at 266, 240, 218, and 200 nm.     

X-ray spectra simulation of Li-like nickel L-shell Ions

The X-ray emission spectra of nickel plasma were simulated under the collisional radiative model (CRM) by using the flexible atomic code (FAC). The dynamical processes including collisional excitation (CE), radiative recombination (RR), dielectronic recombination (DR), collisional ionization (CI) and resonance excitation were considered in the model, and the rate coefficients of DR, RR as well as CI were consistent with previous results within 15%. It was found that the contributions to spectra from cascades and indirect processes could not be ignored. The intensities of spectral lines for lithium-like nickel L-shell ions are sensitive to the electron temperature. The good agreement between present spectral peaks and earlier observed results can be taken as a measure of the accuracy of the present work.     

Resonance modes of layered ferromagnets in a transverse magnetic field

Intensities and positions of resonance lines are calculated for the ferromagnetic resonance spectra of multilayer ferromagnetic films in a magnetic field oriented normally to the film surface. It is shown that the positions of spectral lines depend on the number of ferromagnetic layers, while the line intensities are determined by the phase shift between the oscillations of the magnetic moments of neighboring layers. A qualitative comparison is carried out between the results of calculations and the spectra observed in experiments.     

Quantum-mechanical calculation of the intensity distributions in spectra of resonance hyper-Raman scattering and two-photon absorption of indole and skatole

We have performed a quantum-mechanical calculation of the relative intensities of lines in the spectra of resonance hyper-Raman scattering and two-photon absorption of isolated indole, indole in an aqueous solution, isolated skatole, and skatole-water complex. The effects of hydrogen bonds and intermolecular interaction on the spectra have been considered. Particular features of the intensity distributions in the spectra of indole and skatole have been compared.     

Optical spectrum of a closed cycle MHD generator plasma

The spectra of argon-cesium plasmas, used as working fluids of closed-cycle MHD generators, were investigated in the visible and near-i.r. regions by using a Hilger-Watts medium quartz spectrograph. A number of argon and cesium lines was observed, as well as some lines originating from the impurities present in the cesium capsule. The molecular bands of aluminum monoxide have also been detected. The population temperatures estimated from relative intensities of cesium lines lie below those obtained by using either the line-reversal method or recombination-radiation measurements. The intensities of some neutral cesium lines follow the Boltzmann population relation at the population temperature. The Zeeman effect and reversed profiles of cesium resonance lines were not observed because of low resolution of the spectrograph used and because of light scattering on the film.     

Zum Konzept der charakteristischen Intensitäten der Resonanz-Ramanlinien von Azofarbstoffen

The resonance Raman spectra of the solutions of some azobenzene and hydroxyazonaphthalene compounds were investigated. The relative corrected scattering coefficientsS of the lines have been measured. Assuming the existence of a characteristic intensity, the frequency dependence and the influence of data of the long-wavelength electronic absorption band has been discussed. Testing formulas for intensity dependence in this way it has been shown, that they cannot exactly describe resonance Raman intensities, because there is the problem of the “effective” electronic absorption band. This was studied by comparison of the intensities of several azonaphthalene lines, excited by the mercury lines 4358 and 5461 Å.     

On the role of prepulses during solid target heating by picosecond laser pulses

X-ray emission spectra of the plasma created at the surface of magnesium, aluminum, copper, and zinc targets heated by 1-ps laser pulses with a peak power density of up to 10¹⁶ W/cm² were measured. The effect of a picosecond prepulse on the spectra was studied for various power densities and intensity contrasts of the main laser pulse. It is established that the emission spectra of laser plasmas are weakly affected by a change from 10⁵ to 10⁷ in the main pulse contrast relative to the first prepulse. Variations in the parameters of emission from aluminum and magnesium plasmas were calculated using relative intensities and widths of the resonance lines of H-and He-like ions and their two-electron satellite peaks.     

激光能量对激光诱导Cu等离子体特征辐射强度、电子温度的影响

利用Nd:YAG激光(波长1 064 nm,脉宽10 ns)烧蚀金属Cu靶获得等离子体 .改变激光脉冲能量,观测到Cu的原子谱线和离子谱线随激光脉冲能量有不同的变化关系, 但都在330 mJ/pulse时,谱线强度达到最大,随后在330 mJ～370 mJ/pulse间出现一小平台 ,能量继续增加,各谱线强度减小.同时,使用烧蚀Cu靶产生的五条原子谱线(465.11 nm,5 10.55 nm,515.32 nm,521.82 nm,529.25 nm)的相对强度,在局部热力学平衡近似下,利用B oltzmann图的最小二乘法拟合,测定了不同激光能量下Cu等离子体的电子温度.随激光能量的增加,电子温度近似单调地从1.02×104 K上升到1.46×104 K后,反而有所下降.     

Mossbauer studies of Np hydrides

The Mossbauer spectra of ²³⁷Np in NpH_2+x(x = 0.1, 0.3 and 0.5) consist of several absorption lines which are attributed to Np inequivalent sites corresponding to different numbers of octahedral hydrogen neighbours. The relative intensities of the various lines do not correspond to a random distribution of the hydrogen ions. A model which takes into account first nearest neighbour interactions among octahedral hydrogen ions can reproduce the experimental spectra.     

X-ray spectra from highly ionized dense plasmas produced by ultrashort laser pulses

Hydrogen-like and helium-like X-ray spectra (between 7.1 and 8.2 , i.e., 1500 to 17.50 eV, respectively) from solid aluminium targets irradiated with high intensity (up to 10¹⁷ W/cm²) subpicosecond (0.7 ps) laser pulses have been measured. The spectra show that the resonance lines are very broad and very asymmetric. Evidence for a Doppler-shifted reabsorption of the resonance line emission has been found. The spectra have been simulated by a computer code for the calculation of spectral-line intensities and linewidths. Electron densities exceeding the critical density have been estimated for different laser intensities by comparing the observed and simulated intensity ratio of different dielectronic satellite lines. From the X-ray spectra generated byp- ands-polarized radiation fat different laser intensities, the thresholds for the formation of hydrogen-like and helium-like ions have been determined.     

HL-1装置等离子体真空紫外光谱研究

本文叙述在HL-1装置上做的真空紫外区(300-2000A)光谱实验。用微通道板象增强器摄出了等离子体光谱,对光谱进行了辨认和分析;采用光电法测量了谱线随时间的变化和改变孔栏半径时杂质的变化情况,观察了等离子体发生小破裂时出现的光谱现象,对杂质的来源及某些性质作了分析研究;使用两条CⅣ谱线强度比,测出了放电初期的电子温度。     

Influence of microwave power on EPR spectra of coal macerals

The paper contains a numerical analysis of the electron paramagnetic resonance (EPR) spectra of coal macerals (exinite, vitrinite, inertinite) obtained from Polish medium-rank coal (85.6 wt% C). We determine the lineshapes and the parameters of the component lines, i.e., the intensities and linewidths. As a result, we find that the EPR spectra of the studied macerals are superpositions of broad Gaussian, broad Lorentzian 1 and narrow Lorentzian 3 lines for vitrinite and exinite and two narrow Lorentzian 2 and Lorentzian 3 lines for inertinite. The influence of microwave power on the component lines of the EPR spectrum is studied. A comparison of the results obtained at 223 and 293 K shows that the EPR lines at both temperatures saturate at the same microwave power. It also indicates similar changes of the linewidths with changes of microwave power at both temperatures, a slight increase with increasing microwave power.     

Radiospectroscopic and dielectric spectra of nanomaterials

The shape of lines in the radiospectroscopic (NMR and EPR) and dielectric spectra of materials formed by nanoparticles (hereafter, nanomaterials) is analyzed theoretically. The theory is developed in the framework of the core and shell model according to which a nanoparticle consists of two regions whose properties are affected and unaffected by the surface, respectively. The changes in the resonance frequency, the relaxation time, and the static permittivity due to the surface tension are taken into account, and the Gaussian and Lorentzian shapes of homogeneously broadened lines are considered. The inhomogeneous broadening of the spectral lines is examined for several types of nanoparticle size distributions. It is demonstrated that the splitting of the initial lines in the spectra of bulk systems into pairs of lines with a decrease in the particle size is a specific feature of the spectra of nanoparticles. The intensities and half-widths of the lines are investigated as functions of the parameters of the size distribution of nanoparticles. The results of theoretical calculations are compared with recent experimental data on the ¹⁷O and ²⁵Mg NMR spectra of nanocrystalline MgO. The theoretical dependences of the intensity, the resonance frequency, and the half-width of the spectral lines are in good agreement with the experimental data. The proposed theory offers a satisfactory explanation of the behavior of the static permittivity in BaTiO₃ ceramic materials with nanometer-sized grains.