The harmonic force field of methanol

A 28-parameter harmonic force field for methanol is calculated from the matrix frequencies and frequency shifts of ten isotopic species of methanol determined by Barnes and Hallam; Mallinson and McKean; and Serrallach, Meyer, and Günthard. This present force field reproduces the observed harmonic frequencies and frequency shifts far better than either of the two most recent force fields. The presence of a 20 cm^?1 Fermi resonance shift on the lower A′ CH₃ stretching mode deduced in an earlier work is confirmed here.     

Linear Paul trap design for an optical clock with Coulomb crystals

We report on the design of a segmented linear Paul trap for optical clock applications using trapped ion Coulomb crystals. For an optical clock with an improved short-term stability and a fractional frequency uncertainty of 10^?18, we propose ¹¹⁵In⁺ ions sympathetically cooled by ¹⁷²Yb⁺. We discuss the systematic frequency shifts of such a frequency standard. In particular, we elaborate on high-precision calculations of the electric radiofrequency field of the ion trap using the finite element method. These calculations are used to find a scalable design with minimized excess micromotion of the ions at a level at which the corresponding second-order Doppler shift contributes less than 10^?18 to the relative uncertainty of the frequency standard.     

ESR line shift in NiSnCl6·6H2O at very low temperatures

Electron spin resonance in a single-ground-state magnet, NiSnCl₆·6H₂O, has been studied at temperatures between 83 mK and 4.2 K. Below 1 K, the resonance lines show marked shifts, which can be described quantitatively in terms of exchange shift due to polarization effects treated by McMillan and Opechowski. The shifts give 2J = ?(0.55 ± 0.15) × 10^?2 cm^?1 for the antiferromagnetic exchange interaction among the Ni²⁺ ions in this crystal. The value of 2J is sub-critical in the sense that no spontaneous long-range order can be expected in this singlet-ground-state magnet.     

Resonance magnetoelectric effect without a bias field in a piezoelectric langatate-hysteretic ferromagnet monolithic structure

The frequency, field, temperature, and amplitude characteristics of the direct magnetoelectric effect are studied in a planar monolithic structure consisting of a piezoelectric langatate crystal and a layer of electrolytic nickel. A relation between the magnetic and magnetoelectric properties of the structure is demonstrated, which explains the effects observed in structures with hysteretic layers. At the planar acoustic resonance frequency of the structure (about 70 kHz), the effect amounting to 23 V/(Oe cm) in the absence of a bias field is discovered. In the temperature interval 150–400 K, the amount of the effect changes nearly twofold, the resonance frequency changes by about 1%, and the Q factor on cooling rises to about 8 × 10³. The field sensitivity of the structure is on the order of 1 V/Oe, which makes it possible to detect magnetic fields with an amplitude down to ～10^?6 Oe.     

A Rb-magnetometer for a wide range and high sensitivity

A Rb-magnetometer was constructed for a wide range of application. It uses a very small optically pumped resonance cell with an active volume of less than 0.1 cm³ as the sensor element. The cell is housed in a small probe containing polarizer, rf-coil, heater and photoelement. The pumping light is brought to the resonance cell by use of a 3 m long fibre optics. The magnetometer allows continuous monitoring or stabilizing magnetic fields from about 3·10^?8T to beyond 0.3T. The ultimate sensitivity of the instrument is of the order of 10^?10T. Observing the Hanle signal in the transverse mode of optical pumping the instrument can be used for zero field detection and for the measurement for weak fields by means of field compensation.     

准2-2型磁电多层复合材料的磁电性能

用带底座的Pb（Zr,Ti）O₃薄片阵列作为压电相,Terfenol-D粉末与树脂的混合物作为磁致伸缩相,灌注复合得到准2-2型磁电多层三相复合材料.研究了这种准2-2型多层结构在不同偏置磁场和不同角度下的磁电效应.其面内相互垂直的两个方向磁电电压系数分别在0.15和0.225 T磁场下达到峰值,低频下分别为1.62×10⁵ V·m^-1T^-1和1.75×10⁵ V·m^-1T^-1;而在垂直于面内方向,低频下磁电系数仅有1.3×10⁴ V·m^-1T^-1,体现出显著的磁电各向异性.这种准2-2型磁电多层复合材料具有较好的交流磁场灵敏度,在谐振频率下可以探测到10^-9 T的交流磁场的变化.进行合适的设计和排列,可以探测空间磁场的大小和方向,有望应用于磁场传感器等领域. 关键词： 磁电效应 多铁性 多层复合材料     

Laser acceleration of electrons in a thin metal film

A mechanism acceleration of electrons to relativistic velocities in a thin metal film irradiated with ultrashort (τ _L ≤1 ps) high-power (I>¹⁶ W/cm²) laser pulses is proposed. The acceleration is due to a resonance action of the nonuniform field on a portion of the electrons, viz., those which oscillate in the direction transverse to the film with a frequency close to the frequency of the field. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 8–12 (10 July 1997)     

A far-infrared bolometric observation of the pinned charge-density wave in TTF-TCNQ

The polarized bolometric signal between 5 and 50 cm^?1 from a TTF-TCNQ single crystal near 10 K has been successfully fitted to a Lorentzian oscillator of natural frequency 3.4 ± 0.6 cm^?1 and a damping of 0.05 ± 0.03 cm^?1. This is presumably the phase mode of the pinned charge-density wave, with interchain Coulomb interaction probably being responsible for the pinning. The low damping is thought to be due to two-phonon “difference” processes, which are also thought to be responsible for a temperature-dependent feature at 25 cm^?1. No dependence of the pinned-mode frequency on electric field could be detected.     

Helicon resonance in zinc

The dimensional resonance of helicon waves has been observed in Zn for the magnetic field direction along [0001]. The resonance is associated with uncompensated carriers produced by the magnetic breakdown between electron and hole orbits near the K point. The uncompensated carrier concentration has been determined as 3.5 × 10²² cm^?3.     

Dynamic frequency shift in the E.S.R. spectra of transition metal ions

The factors which determine the electron spin resonance lineshapes and shifts of transition metal complexes in solution are discussed. It is shown that for ions with S > ½ the dynamic frequency shift may have pronounced effects on the E.S.R. lineshapes, and experimental evidence for this effect in complexes of Cr³⁺, Fe³⁺ and Gd³⁺ is presented. A quantitative interpretation of these spectra in terms of a relaxation mechanism due to fluctuation of the quadratic zero field splitting interaction is given.     

Study of anharmonic effects in the IR spectrum of a solution of CF<Subscript>3</Subscript>Br in liquid argon

The vibrational spectrum of CF₃Br with the natural abundance ratio of isotopologues is studied in solutions in liquid Ar at T = 90 K in the frequency range 4000–400 cm^?1 with a resolution of 0.1 cm^?1 for the concentration range 3.1 × 10^?7?6.3 × 10^?3 mol %. The parameters of the vibrational spectrum of the molecule are determined: the frequencies are measured accurate to ± 0.1 cm^?1, and the transition probabilities are found up to the fourth order inclusive. One hundred fifty absorption bands of CF₃Br are interpreted, including the bands belonging to all the isotope modifications of this compound; the halfwidths of these bands are determined. For all the fundamental frequencies, the isotope shifts are obtained. Vibrational ?-resonance is studied. Using the experimental data obtained and taking into account this resonance, a complete set of parameters describing the experimental frequencies with the error δ ≈ 0.3 cm^?1 was found. This set consists of 6 harmonic frequencies and 30 anharmonicity constants, including the constants r _ik related to vibrational ?-resonances.     

Infrared spectra of matrix-isolated sodium and potassium cyanides

The infrared spectra of matrix-isolated sodium and potassium cyanides in neon, argon, krypton, and nitrogen matrices were examined over the range 4000 cm^?1 to 33 cm^?1. The effect of temperature cycling, which normally results in migration of trapped molecules to generate polymeric species, has been pursued. A careful study of the effect of superheating the vapor species on the spectra has also been carried out. By these means it has been possible to identify the bands in the spectrum due to monomeric and polymeric species. Isotopic frequency shifts were measured for a ¹³C-enriched sample of sodium cyanide and ¹³C- and ¹⁵N-enriched samples of potassium cyanide. From the measured isotopic shifts it was possible to determine the structure of these two compounds as being linear NaCN and KCN. Accurate force constants were calculated using the measured frequency values for the three fundamental vibrational modes of the different isotopic molecules of NaCN and KCN. Bands due to sodium and potassium cyanates were also identified in some of these systems. ¹³C and ¹⁵N isotopic frequency shifts were also observed for NaOCN and KOCN.     

Vordurchschlagsphänomene der Feldemission im Nanosekundenbereich

Variation of field emitters on Mo- and Cu-cathodes were investigated by field emission microscopy after application of nanosecond voltage pulses. The emitters delivered emission currents with densities of more than 10¹³ Am^?2 without breakdown. Heating by these currents caused desorption and melting of emitter tips. From the desorption events resonance tunneling was deduced with typical UHV-conditions. Melting caused blunting of the emitters. Hence sharp micro-points exploded only by sufficiently fast heating (with time constants ≦ 1 ns) or by secondary effects due to contaminations. By introduction of air in the pressure region of 10^?4 - 10^?3 Pa new emitting sites appear with time constants of about 10^?8 s, probably by formation of oxides.     

Raman scattering from 6Li+ and 7Li+ ions in lithium beta-alumina

Raman bands due to translational modes of ⁶Li⁺ and ⁷Li⁺ ions in beta-alumina were found in the frequency range of 340–410 cm^?1, which is much higher than expected from the corresponding values reported for other alkali-metal ions (20–100 cm^?1). Based on a model calculation, it is believed that the large shifts to higher frequencies are due to deviations of the Li⁺ ions from the mirror plane into “pocket sites” formed by oxygen ions above or below the Beevers-Ross sites     

Dirac-neutrino magnetic moment and the dynamics of a supernova explosion

The double conversion of neutrino chirality ν_L → ν_R → ν_L has been analyzed for supernova conditions, where the first stage is due to the interaction of the neutrino magnetic moment with plasma electrons and protons in the supernova core, and the second stage, due to the resonance spin flip of the neutrino in the magnetic field of the supernova envelope. It is shown that, in the presence of the neutrino magnetic moment in the range 10^?13 μ_B < μ_ν < 10^?12 μ_B and a magnetic field of ～10¹³ G between the neutrinosphere and the shock-stagnation region, an additional energy of about 10⁵¹ erg, which is sufficient for a supernova explosion, can be injected into this region during a typical shock-stagnation time.     

A high-precision segmented Paul trap with minimized micromotion for an optical multiple-ion clock

We present a new setup to sympathetically cool ¹¹⁵In⁺ ions with ¹⁷²Yb⁺ for optical clock spectroscopy. A first prototype ion trap made of glass-reinforced thermoset laminates was built, based on a design that minimizes axial micromotion and offers full control of the ion dynamics in all three dimensions. We detail the trap manufacturing process and the characterization of micromotion in this trap. A calibration of the photon-correlation spectroscopy technique demonstrates a resolution of 1.1 nm in motional amplitude of our measurements. With this method, we demonstrate a sensitivity to systematic clock shifts due to excess micromotion of $|(\Updelta\nu/\nu)_{\rm mm}|=7.7\times10^{-20}$ along the direction of the spectroscopy laser beam. Owing to our on-board filter electronics on the ion trap chips, no rf phase shifts could be resolved at this level. We measured rf fields over a range of 400 μm along the ion trap axis and demonstrated a region of 70 μm where an optical frequency standard with a fractional inaccuracy of ≤1 × 10^?18 due to micromotion can be operated.     

Die Winkelabhängigkeit der Resonanzstreuung niederenergetischer Elektronen an He,Ne, Ar und N2

The energy dependence of the elastic resonance scattering of low energy electrons from He, Ne, Ar, and N₂ has been measured in the angular range from 8° to 110°. From the measurements are derived the total angular momenta and hence the configurations of the quasistationary negative ion states. The line shapes depend very strongly on the phase shifts for the potential scattering and on the interference of different partial waves. In the cases of He and Ne phase shifts are determined. The resonance structure in the elastic scattering from N₂ in the energy range from 1.75 eV to about 3,5 eV seems to be due to the formation of the N ₂ ^? -ion in its electronic ground state with a²Π configuration. The separations of its first few vibrational states are 237±10 meV, the natural half-width of these states being approximately 150 meV.     

Dynamical XPS measurements for probing photoinduced voltage changes

Photoillumination with 405 nm laser causes shifts in XPS peaks of n-Si(100), and CdS. To distinguish between surface photovoltage (SPV), and charging, dynamical measurements are performed, while sample is subjected to square wave pulses of ± 10.00 V amplitude, and 10^?3–10⁵ Hz frequency. For n-Si, Si2p peaks are twinned at + 10.00 and ?10.00, yielding always 20.00 eV difference. Photoillumination shifts the twinned peaks to higher energies, but the difference is always 20.00 eV. However, for CdS, the measured binding difference of Cd3d peaks exhibits strong frequency dependence due to charging, which indicates that both fast SPV and slow charging effects are operative.