Sorption experiments with water spin isomers in glycerol

Sorption experiments with water/glycerol solution were performed by measuring the ortho/para content in saturated water vapor using the 1-THz BWO spectral method. The results were interpreted as detection (i) of preferential fugacity of ortho molecules from the glycerol surface and (ii) the ability of glycerol to keep the deviation from 3:1 normal ortho/para water ratio for unexpectedly long time (several weeks for 0.5 % water concentration).     

Submillimeter BWO spectroscopy of solids

The potentialities of submillimeter spectroscopy (3–30 cm^–1) based on backward wave oscillators for studying solids are discussed. The scope of the research on this problem made at the Institute of General Physics of the USSR Academy of Sciences is outlined.     

Laser spectroscopy of high spin isomers – a review

This review summarizes the experimental data on charge radii differences among ground state and high spin isomeric states determined by high-resolution laser spectroscopic methods. A comparison is presented between radii changes obtained from the isomeric shifts in the atomic spectra and from the quadrupole moments of both ground and isomeric states under the assumption that the radii changes are determined by the difference of the quadrupole deformations. Special attention is paid to isomers arising from the break-up of nucleon pairs and isomers of odd–odd nuclei. The characteristic features of the radii changes for isomeric states of different origin are discussed.     

Selective adsorption of water spin isomers under laser excitation

The experiment on water molecule adsorption on the surface of nanoporous polymeric adsorbent in the Knudsenmode under conditions of selective action of IR radiation is described. Resonant excitation of the vibrational-rotational transition of the ortho-modification of H₂O molecules at a wavelength of 1.85 µm is used. The applicability of this method to the production of water vapor with nonequilibrium concentration ratios of ortho and para modifications of water molecules is shown.     

Rotational parity and separation of water molecules into spin isomers

A theoretical explanation is proposed for the effect of variations in concentration of water molecule spin isomers in the gas phase during the interaction of molecules with a solid adsorbent surface. The explanation is based on antisymmetric (AS) correlation between proton spin moments and molecule rotation. A new AS correlation occurs during the interaction of the molecule with a dc electric field near the surface. Due to the new (external) AS correlation, ortho-and parawater molecules are formed; separation into spin modifications occurs over degenerate states of each rotational level of the molecule. Water molecule separation into spin modifications at the previous (internal) AS correlation occurs over rotational levels of molecules. The ratio of ortho-and parawater concentrations in the gas phase at the external AS correlation is compared with experimental data on chromatographic separation of water spin isomers. Quantitative agreement is observed between the calculated ratio and the ratio measured for water molecules at the final separation stage.     

Methods of terahertz-subterahertz BWO spectroscopy of conducting materials

This paper considers present spectroscopic methods developed for measurement of dielectric response (conductivity and permittivity spectra) of condensed media in the terahertz-subterahertz spectral regions. The techniques based on the use of BWO spectrometers and designed for direct quantitative measurements (without invoking the Kramers-Kronig relations) in the terahertz-subterahertz frequency range (0.03–1.45 THz) of the conductivity σ(ν) and permittivity ?′(ν) spectra of conducting and absorbing materials are described. The techniques are based on measuring the amplitude and phase of the transmission coefficient of film samples on dielectric substrates and the reflection coefficient of a reference plane-parallel dielectric plate contacting the surface of the sample under study. The use of these techniques in measurement of the σ(ν)) and ?′(ν) spectra of conductors and superconductors is illustrated with examples.     

Quadrupole moments of high spin isomers studied by level mixing spectroscopy (LEMS)

This paper intends to introduce the reader into Level Mixing Spectroscopy (LEMS), and to the results obtained with it so far. LEMS is a rather recent method used to study the quadrupole interaction of isomeric states in solid hosts, and was developed at Leuven. After an introduction dealing with both the theoretical background and the experimental set-up, a detailed comparison will be made with the Time Differential Perturbed Angular Distribution (TDPAD)-method. It turns out that LEMS is well suited for very high spin states in the ns-ms lifetime region. In the second part, the results in isotopes of Bismuth (10⁻-isomers in^202-204-206Bi and the 21/2⁺-state in²⁰⁷Bi), Astatine (²¹¹At, 29/2⁺-and 39/2⁻-states;²¹⁰At, 15⁻-and 19⁺-isomers;²⁰⁹At, 29/2⁺-isomer and²⁰⁸At, 16⁻-level) and Francium (²¹³Fr, 29/2⁺-and 65/2⁻-levels;²¹²Fr, 15⁻-and 27⁻-states and²¹¹Fr, 29/2⁺-and 45/2⁻-isomers) are discussed. The spin values range from 10 up to 65/2 and the lifetime region extends from 70 ns up to 13 ms, which proves already the applicability of LEMS. The results will also be compared to other data known so far in the²⁰⁸Pb-region.     

Mixed state of spin moments of two protons in the water molecule and stability of its spin isomers

It is shown that the para-to-ortho water ratio most abundant in the nature is the water molecule existence form most stable to external influences. The assumptions, which are implicitly adopted when singlet and triplet states of the quantum system of two spin moments are independently considered, are discussed.     

Selective alignment of molecular spin isomers

We experimentally demonstrate field-free, spin-selective alignment of ortho- and para molecular spin isomers at room temperature. By means of two nonresonant, strong, properly delayed femtosecond pulses within a four wave mixing arrangement, we observed selective alignment for homonuclear diatomics composed of spin 1/2 (15N) or spin 1 (14N) atoms. The achieved selective control of the isomers' angular distribution and rotational excitation may find applications to analysis, enrichment, and actual physical separation of molecular spin modifications.     

Temperature evolution of the relative concentration of the H2O ortho/para spin isomers in water studied by four-photon laser spectroscopy

The four-photon laser spectroscopy of molecular motions [1] of distilled water in the terahertz and subterahertz spectral ranges is employed to observe resonant lines related to the rotational transitions of ortho and para nuclear spin isomers of the H₂O molecule. It is demonstrated that the intensity ratio of the lines of the H₂O ortho/para spin isomers in several water samples decreases by a factor of 2.0–2.5 in comparison with the gas-phase ratio. A violation of the equilibrium ortho/para ratio upon the condensation of vapor is interpreted as a manifestation of the spin selectivity in the formation of the H-bonded complexes of the H₂O para isomers. The nonequilibrium ortho/para ratio characterizes water at room temperature as an unstable liquid with respect to the spin temperature.     

Thermal desorption spectroscopy of he from Ni at and below saturation

Trapping of helium after implantation at energies of 8 to 150 keV and fluences up to 10¹⁹ He-ions/cm² in nickel at room temperature is studied by measuring the thermal desorption spectra during linear heating up to 1000°C. At several annealing stages the trapped helium is measured by means of the nuclear reaction ³He(d, α)H and the target surface is observed by laser scattering and with the scanning electron microscope.

The thermal desorption spectra depend strongly on the implantation fluence but only slightly on the implantation energy, indicating a similar trapping of He in the lattice for the implantation energies used here, The temperature at which desorption starts decreases with increasing fluence. Above the critical fluence for blistering an additional low temperature (150°C) desorption maximum is found.

The desorption peak at 150°C can be approximated theoretically with a single jump desorption process of first order and a Gaussian distribution of activation energies around 1 eV. The measurements indicate that at higher temperatures (>300°C) helium desorption is partly due to the opening of helium bubbles at the target surface.     

基于开槽单矩形栅和圆形电子注的W波段返波振荡器

提出将开槽单矩形栅和圆形电子注作为 W波段返波振荡器的注波互作用回路. 使用 3维电磁场仿真软件CST-MWS对开槽单矩形栅的高频特性进行了仿真分析, 研究结果表明: 相对于传统单矩形栅, 新结构的基模带宽有所展宽; 基模与高次模发生模式竞争的可能性很小; 在采用圆形电子注时新结构能获得大得多的耦合阻抗; 新结构的趋肤损耗略有改善. 将该慢波结构应用于设计一支以94 GHz为频带中心的W 波段返波振荡器: 设计了简洁的慢波过渡部分、输出耦合器和终端匹配衰减器, 优化参数后获得了良好的信号传输特性; 利用粒子模拟软件CST-PS对返波振荡器模型进行了三维大信号注波互作用计算, 设定合适的电子注电流等参数后, 调整工作电压在较宽的频带内获得了瓦级的功率输出, 电子效率在整个频带范围内优于1%. 关键词： 开槽单矩形栅 圆形电子注 返波振荡器 W波段     

Femtosecond laser induced desorption of water from silver nanoparticles

The photodesorption mechanism of H₂O from quartz-supported silver nanoparticles has been studied by femtosecond laser two-pulse correlation and fluence dependence measurements. With the laser wavelength close to the maximum of the (1,1) plasmon resonance of the nanoparticles, the desorption was found to be purely thermal, i.e., induced by coupling of the desorption coordinate to the nanoparticle lattice temperature, both in the low- and the high-coverage regimes. The lattice cooling times of the nanoparticles are in the range of several hundred ps, in accordance with recent time-resolved X-ray measurements. Also observed is a reversible red-shift of the nanoparticle plasmon modes with increasing H₂O coverage which is attributed to dielectric screening. PACS 78.67.-n; 82.53.-k; 65.80.+n     

High spin spectroscopy of 139Pr

The high spin states in N=80 ¹³⁹Pr have been investigated by in-beam γ-spectroscopic techniques following the reaction ¹³⁰Te (¹⁴N, 5n) reaction at E=75 MeV, using a gamma detector array, consisting of seven 23% compton-suppressed high purity germanium detectors and a multiplicity ball of fourteen bismuth germanate elements. Based on γ-γ coincidence data, the level scheme of ¹³⁹Pr has been considerably extended up to 7.2 MeV excitation. Tentative spin-parity assignments are done for the newly proposed levels on the basis of the DCO ratios corresponding to strong gates and the available information from the earlier light ion experiments.     

Terahertz spectroscopy of AuFe spin glasses

The electrodynamic response of spin glasses (in the form of thin AuFe films) in the terahertz frequency range has been studied using backward-wave oscillator (BWO) spectroscopy (10–40 cm^?1) and optical ellipsometry (5000–33000 cm^?1) techniques at temperatures from 5 to 295 K. The room-temperature dynamic conductivity spectra of AuFe films are typical of metals and can be described within the framework of the Drude theory of conduction by free charge carriers. Changes in the microscopic parameters of charge carriers in AuFe films with increasing iron content, which are related to additional scattering of carriers on the impurity magnetic moments, have been studied on the quantitative level, including the carrier relaxation frequency and characteristic time, plasma frequency, and conductivity. It is established that the spin-glass phase at a temperature of ～5 K exhibits dispersion of the conductivity in the frequency range 10–40 cm^?1, which can be related to the appearance of a mobility gap in the subsystem of free electrons involved in the RKKY interaction between magnetic centers (Fe atoms).     

太赫兹光谱技术在四氢双环戊二烯检测中的应用

研究了太赫兹光谱技术在鉴别含能材料同分异构体中的应用。首先研制了适于特定工程应用的太赫兹时域光谱仪样机,并经过振动冲击、高低温试验验证了样机的环境适应性,表明该款样机完全可以在非实验室环境下稳定可靠地工作。利用一氧化碳标准气体验证了样机测量光谱的正确性,并同时实现了对样机测量频率的校准;利用校准后的光谱仪测量了四氢双环戊二烯的两种同分异构体endo-THDCPD和exo-THDCPD的太赫兹光谱,测量结果显示两种不同构型材料的太赫兹光谱存在显著差异,endo-THDCPD的太赫兹光谱在0.23 THz和1.70 THz处呈现出明显的特征吸收,exo-THDCPD的2个最明显的特征吸收峰则位于1.41 THz和1.74 THz。该结果表明:运用太赫兹光谱技术可有效区分这两种分子结构仅存在微弱差异的材料,对太赫兹光谱在含能材料研究领域的应用具有参考意义。     

Chemisorption of halogens on silver a critical comparison of results from photqemission and thermal desorption spectroscopy

Conflicting thermal desorption (TDS) results from submonolayer coverages of atomic Cl, Br or I on Ag(100), Ag(110) or Ag(111) stimulated us to check for the possible influence of different sample preparation procedures. We present experimental evidence, that a combined approach using TDS and angle-resolved ultraviolet photoemission may help to distinguish between better and worse surface preparation. We present detailed new results for the Cl/Ag(110) system. From our observations we conclude that all three halogens listed above give one and only one TDS peak in the submonolayer regime and show very similar adsorption/desorption-characteristics. This fact removes the apparent contradictions reported in the literature and demonstrates that the halogen-Ag bond is not very sensitive to the surface crystallography.     

Study on the dispersion characteristic of the plasma-loaded relativistic BWO

The dispersion characteristic of the plasma-loaded relativistic backward wave oscillator has been analyzed. The theoretical model has been established and the numerical calculations accord with the experimental results, which provides some useful suggestions on the designing of slow-wave structure of BWO.     

Caprolactam and nitrobenzene desorption from polymeric sorbents by subcritical water

Subcritical water is tested as an agent for caprolactam and nitrobenzene desorption from the hyper-cross-linked polystyrene sorbents MN-202 and MN-270. The efficiencies of desorption of these two compounds by subcritical water and by a water solution of isopropanol are compared.