Inversion-rotation interaction in NH2D: Intensity perturbations in the ν2 band

The parameters of NH₂D in the ground and ν₂ states have been refined by a simultaneous analysis of the microwave, FTIR, and diode laser data. The intensities of 46 NH₂D lines have been measured, and from a least-squares fit of the intensity data the a ← s, s ← a, s ← s, and a ← a transition moments have been derived. The intensities of the lines in the ν₂ band of NH₂D have been calculated taking into account the inversion-rotation interaction. The accuracies of the wavenumbers and intensities calculated with the new parameters are estimated to be better than ±0.0002 cm⁻¹ and ±5%, respectively. The matrix elements for interaction of vibrations through x, y, and z axis couplings are appended.     

Color centers in the ionized and in the triplet state —Z 2 centers in calcium doped KCl crystals

Optical absorption measurements ofZ ₂ andZ ₂ ⁺ centers in KCl:Ca are combined with electron spin resonance experiments in order to reveal the electronic and atomistic structure of these centers.Z ₂ ⁺ centers are alignable in the crystal by polarized optical irradiation at suitable temperatures. From orientedZ ₂ ⁺ centers equally orientedZ ₂ centers can be produced, both types of centers showing a (100) axial symmetry. ConcerningZ ₂ this is also confirmed by ESR measurements on their triplet state produced by optical excitation. Polarized excitations allow a determination of the ratio of oscillator strengths for transitions parallel and perpendicular to the center axis using the variations in ESR line intensities. ForZ ₂ f /f =1.6 is found in this way; decomposition of the dichroism ofZ ₂ ⁺ centers gives for this speciesf /f =1.8. It is shown that theZ ₂(Ca) center is a molecule made up of a Ca⁺⁺ ion and an anion vacancy in (100) nearest neighborhood, sharing two electrons with antiparallel spins in the ground state. Both, withZ ₂ andZ ₂ ⁺ , the absorption bands at lowest energies are best explained bys—d charge transfer transitions.     

Scaling of the temperature-dependent resistivity in SrFe2−xNixAs2

We show that the zero-field normal-state resistivity of temperature-dependent resistivity ρ(T) of SrFe_2?xNi_xAs₂ can be reproduced by the expression ρ(T) = ρ₀ + c T exp(?2Δ/T). ρ(T) can be scaled using both this expression where the energy scale Δ, c and the residual resistivity ρ₀ are scaling parameters and a recently proposed model-independent scaling method (H.G. Luo, Y.H. Su, T. Xiang, Phys. Rev. B 77 (2008) 014529). The scaling parameters have been calculated and the compositional variation of 2Δ(x) has been determined. This dependence show almost a linear decreasing in the underdoped regime similar to that reported for cuprates. The existence of a universal metallic ρ(T) curve in a wide temperature range which, however, is restricted for the underdoped compounds to temperatures above a structural and anitiferromagnetic transition is interpreted as an indication of a single mechanism which dominates the scattering of the charge carriers in SrFe_2?xNi_xAs₂ (x = 0–0.3).     

Progress in the Secondary Heating System for the HL-2A Tokamak

In 2006, the following work on secondary heating systems for HL-2A tokamak have been done： the development of an electron cyclotron resonance heating （ECRH） system, the improvement of lower hybrid resonance heating （LHCD） system and the fabrication on neutral beam injection （NBI） system.     

Pellet Injection Experiments in the HL-2A Tokamak

The advantages of pellet injection as a competitive means of fuelling a tokamak are well known. They include： （ 1 ） deep deposition of fuel, （ 2 ） better fuelling efficiency, （ 3 ） purer plasma, and so on. Meanwhile, improving plasma performance by pellet injection has been proven in many tokamak experiments. The deposition of pellet particles following pellet injection causes a temporal change of the local plasma temperature and density gradients which affects the transport properties of the plasma, so pellet injection can be used as a method of studying the transport process as well.     

Angular distributions of electrons in the (γ, 2e) reaction andee-correlations in the atom

The cross sectionsd ³ σ/dE ₁ d n ₁ d n ₂ for the Ar (γ, 2e) Ar⁺⁺ process are calculated on the basis of the diagram approach within the energy intervalω=400–650 eV as functions of the angleθ ₁₂ between final electrons with equal energiesE ₁=E ₂ for several levels of the final Ar⁺⁺ ion. It has been elucidated that the interference of amplitudes corresponding to the interaction in the final and initial states is of prime importance. The angular distributions over the angleθ ₁₂ are very sensitive to the term of the final ion. There are numerous data for the experimental verification of the theory, in particular, for the selection of leading diagrams. The (e, 3e) experiment is also desirable.     

“Superslow” processes in the Ge-GeO2 system

A study was made of the charged state on a natural or an oxidized germanium surface during heat-and-field treatment. This study dealt with the kinetics of charging and discharging of superslow surface states. The thermal activation energy of these charging and discharging processes has also been evaluated. Conclusions are drawn about the possible nature of superslow traps in the Ge-GeO₂ system.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No.2, pp.79–86, February, 1976.In conclusion, the authors thank V. F. Kiselev for the useful discussion of this report and his valuable comments.     

Two triple points in the H2O–H2 system

Using a volumetric technique, phase transitions in the H₂O–H₂ system were investigated in the vicinity of two points of an invariant equilibrium, L+I _h+sII and L+sII+C ₁, located at 1.07 kbar and?10 °C and at 3.6 kbar and 1 °C, respectively. Liquid water (L), low-pressure hexagonal ice (I _h) and high-pressure cubic (sII) and rhombohedral (C ₁) clathrate hydrates were in equilibrium with gaseous hydrogen taken in excess.     

Pressure-Broadened Linewidth Measurements in the ν2Band of the CH3Radical

Pressure broadening coefficients for an infrared transition of the methyl radical have been measured for the first time. CH₃radicals, generated by pyrolyzing di-tert-butyl peroxide in a flow of either N₂or Ar, were probed using a tunable diode laser and a multipass absorption cell. The Lorentz half-width of theQ(6,6) line of the ν₂band of CH₃at 607.024 cm⁻¹was measured as a function of pressure at 295 K. The broadening coefficients (HWHM) areb(Ar) = 0.0310 ± 0.0012 cm⁻¹atm⁻¹andb(N₂) = 0.0390 ± 0.0020 cm⁻¹atm⁻¹. These coefficients are lower than those for CH₄–Ar, N₂broadening. This may be due to a lower polarizability or smaller effective hard collision diameter for CH₃relative to CH₄.     

Parity nonconservation in the circular polarization of primary photons of the radiation accompanying electron conversion in the 5/2− → 5/2+ nuclear transition in the 229Pa91 nucleus

The ground state of ²²⁹Pa₉₁ is a 5/2^± doublet, with the splitting energy being 220+-50 eV. A direct observation of P-odd effects in this system is of great interest, since this may furnish information about the parity-nonconserving effective one-nucleon potential. Since a transition between two oppositeparity doublet states is accompanied by a strong conversion, it is possible to study P-odd mixing by exploring the conversion-electron helicity and the circular polarization P _γ of the lines of atomic radiation that arises upon the filling of a hole in the 6s _1/2, 6p _1/2, and 6p _3/2 shells of the ²²⁹Pa₉₁ atom. Since P _γ is about 3–5% for individual atomic transitions, experiments aimed at observing parity-nonconservation effects on this basis are feasible.     

Line coupling in the temperature and frequency dependences of absorption in the microwindows of the 4.3 μm CO2 band

The shapes of the self- and N₂-broadened ν₃CO₂ fundamental vibration-rotation band in the microwindows (troughs between the lines) have been measured at various temperatures. Important deviations with respect to the superposition of Lorentzian profiles are observed. These deviations are interpreted in terms of line coupling, which redistributes the intensity in the whole band. In order to take into account this line coupling, two models are considered within the frame of the impact theory. The first model uses the strong-collision approximation to describe the rotational energy transferred by collisions. It leads to a simple analytical expression for the band profile. The second model is based on the exponential-gap law. These two models account well for the frequency dependence of the measured absorption in the microwindows and for the temperature dependence in the case of the N₂-broadened CO₂ band but not in the self-broadened case. The influence of the line-coupling rotational distribution, which differs significantly in the two models, is discussed. The possible role of the finite duration of collision in rotational energy transfer is examined.     

Studying parity-nonconservation effect in the conversion transition between the levels of the (5/2)± doublet in the 229Pa nucleus

Effects of weak nucleon interaction are calculated for the ground-state doublet of 5/2^± levels of the strongly deformed nucleus ²²⁹Pa₉₁. A parity-nonconservation effect in the doublet states can be observed in the conversion spectrum for the isomeric transition between the doublet levels. By using a generalized model of the nucleus, the matrix element of the effective one-nucleon weak-interaction potential, which determines the weight of the opposite parity admixture in the doublet components is estimated in the single-particle approximation. The reduced probabilities of the E1 and M1 nuclear transitions between the doublet states are calculated within various models of the deformed nuclear potential. The effect of Coriolis forces on the dipole electric transition in question is considered. The lifetime of the upper doublet state is estimated.     

Parity violation in the 17/2−–17/2+ doublet in93Tc

The parity-violating mixing of the 17/2^– and 17/2⁺ levels in⁹³Tc nuclei, polarized by the tilted multifoil interaction, was measured by the observation of the forward-backward-ray asymmetry. The nuclear polarization, induced by the tilted multifoils, was measured directly for the neighboring^88,90Zr isomers. The forward to backward asymmetry was determined to be A=(2.5±2.1) 10^–3 which implies a parity violating matrix element ¦H _PV )¦=(4.0±3.7)meV.     

Transition probabilities in the C2 ∑+-X2 II system of CH

Relative Einstein emission coefficients are measured for several bands of the C²∑⁺-X² II system of the CH radical, using laser-induced fluorescence in an atmospheric pressure flame. The results are compared with theoretical calculations; a previously calculated ab initio electronic transition moment, together with Morse wave functions, forms an excellent representation of the experimental results.     

Siliconization for Wall Conditioning in the HL-2A Tokamak

The sputtering of impurities is caused by the interactions between plasma and the first wall, and the recycling of the gas affects the particle and energy transport of plasmas with a complicated mechanism in plasma operation. It is important for present tokarnaks to achieve a good confinement and high performance plasmas by means of controls of the vacuum condition, usage of low Z materials, control of the recycling of neutral particles and suppressions of the appearances and yield of impurities. For higher plasma parameters, some of the first wall of HL-2A is covered with graphite materials and carbon fiber tiles. Hence the studies on the in-situ coating application and development, and the interactions between the coating film and plasma are needed to effectively control the impurity, improve plasma confinement and achieve high performance plasma.     

Entanglement in the supermolecular dimer [Mn4]2

This paper investigates the entanglement in the supermolecular dimer [Mn4]2 consisting of a pair of single molecular magnets with antiferromagnetic exchange-coupllng J. The conventional yon Neumann entropy as a function of the exchange-coupling is calculated explicitly for all eigenstates with the quantum number range from M = M1 ＋ M2 = -9 to 0. It is shown that the yon Neumann entropy is not a monotonic function of the coupling strength. However, it is significant that the entropy of entanglement has the maximum values and the minimum values for most eigenstates, which is extremely useful in the quantum computing. It also presents the time-evolution of entanglement from various initial states. The results are useful in the design of devices based on the entanglement of two molecular magnets.     

Fundamental Concepts of Electron Spin Resonance Technique in the Determination of the Crystal Field Structure of O− 2 Ions in TiO2

Abstract

The basic principles of Electron Spin Resonance (ESR) as applicable in crystal field characterization of paramagnetic species has been outlined. Fundamental concepts of the precessional motion of electrons and their magnetic moments at resonance were developed. The theory of ESR based on the response of unpaired electron(s) as they undergo spin-spin or spin-lattice relaxation when subjected to strong external magnetic fields was examined. Ions of the O^? ₂ group adsorbed on TiO₂ were studied using a Varian Spectrometer. The resulting spectral diagrams obtained were used in calculating the g-factors which gave results for orthorhombic crystal symmetry for O^? ₂ ions in TiO₂.     

Spin splittings in the ν3 band of NO2

Spin splittings for several important atmospheric lines in the ν₃ band of NO₂ have been measured by diode laser. An improved spin-splitting program has been developed which takes into account the asymmetry effects in the lower K_a splittings. The measured spin splittings and the derived spin-rotational constants are reported in this study to a much higher accuracy than previously achieved.     

Contributions of the Two Nuclei to the Harmonic Generation in H2＋ Molecules

The separate contributions of the two nuclei in H2＋ to the harmonic generation are investigated by numerically solving the time-dependent Schroedinger equation. The results show that the diverse electron distributions around the two nuclei under the effect of a laser field lead to different contributions of the two nuclei to the harmonic generation in different times, i.e., the contribution mainly comes from nucleus A around the （n ＋ 0.5） optical cycle while from nucleus B around the n optical cycle. By means of the time-frequency distributions and the coupled electron nuclear wave-packet density distributions, the physical mechanism is discussed in detail.