14N and35Cl nuclear quadrupole coupling constants in thiazyl chloride from microwave spectroscopy andab initio molecular orbital computations

Summary The¹⁴N and³⁵Cl nuclear quadrupole coupling constants of the¹⁴N³²S³⁵Cl isotopic species of thiazyl chloride have been determined from an analysis of the hyperfine structure of sixμ _a andμ _b transitions in the microwave spectrum as (in MHz) _χaa (³⁵CL) = −39.00(3), _χbb (³⁵CL) = 23.84(4), _χaa (¹⁴N) = −1.42(6), _χbb (¹⁴N) = −4.16(6).

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Riassunto Le costanti di accoppiamento quadrupolare di¹⁴N e³⁵Cl della specie isotopica¹⁴N³²S³⁵Cl del tiazil cloruro sono state determinate attraverso l'analisi della struttura iperfine di sei transizioni di tipoμ _a eμ _b dello spettro a microonde. Si sono ottenuti i seguenti valori (in MHz): _χaa (³⁵CL) = −39.00(3), _χbb (³⁵CL) = 23.84(4), _χaa (¹⁴N) = −1.42(6), _χbb (¹⁴N) = −4.16(6).

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Резюме Из анализа сверхтонкой структуры шестиμ _a иμ _b переходов в микроволновом спектре определяются ядерные квадрупольные константы связи¹⁴N и³⁵Cl в¹⁴N³²S³⁵Cl. Получены следующие значения (в МГц): _χaa (³⁵CL) = −39.00(3), _χbb (³⁵CL) = 23.84(4), _χaa (¹⁴N) = −1.42(6), _χbb (¹⁴N) = −4.16(6).kg]PACS. 33.20

     

Search for exotic contributions to atmospheric neutrino oscillations

The energy spectrum of neutrino-induced upward-going muons in MACRO has been analyzed in terms of effects of violating relativity principles, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of ν _μ → ν _τ transitions. The data disfavor these exotic possibilities even at a subdominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter |Δυ| < 6 × 10⁻²⁴ at sin(2ϑ_υ) = 0 and |Δυ| < (2.5–5) × 10⁻²⁶ at sin(2ϑ_υ) = ±1. These limits can also be reinterpreted as upper bounds on the parameters describing violation of the equivalence principle. The text was submitted by the author in English.     

Microscopic study of low-lying yrast spectra in <Superscript>100–108</Superscript>Mo isotopes

Variation-after-projection (VAP) calculations in conjunction with Hartree-Bogoliubov (HB) ansatz have been carried out for A=100−108 molybdenum (Mo) isotopes. In this framework, the yrast spectra with J _max ^π ≥10⁺, B(E2) transition probabilities, quadrupole (β₂) and hexadecapole (β₄) deformation parameters, moment of inertia (I) and square of cranking frequency (ω²) for even-even Mo isotopes have been obtained. The results of the calculation give an indication that it is important to include the hexadecapole-hexadecapole component of the two-body interaction for obtaining various nuclear structure quantities in these Mo isotopes.     

Optical properties of the ternary compound Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Se:Co

We present the results of experimental studies of the optical properties of cobalt-doped Cd _x H_1−x Se (x = 0.18) single crystals with cobalt ion concentrations of NCo = 5·10¹⁸, 5·10¹⁹, and 1·10²⁰ cm⁻³ at T = 90 K and 300 K. The composition (x = 0.18) of the Cd _x Hg_1−x Se solid solution was selected so that the hypothetical resonance level is found on the bottom of the conduction band. We show that the cobalt ions in the mercury selenide can form a resonance donor level only for cobalt concentrations N_Co < 5·10¹⁸ cm⁻³. For N_Co ∼ 5·10¹⁸ cm⁻³, the cobalt ions substitute for mercury atoms, forming a solid solution and leading to an increase in the bandgap width and a change in the physical properties. The solubility of cobalt in the HgSe lattice can be greater than 5%–10%. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 73–77, January–February, 2007.     

Simulation study of χc→J/Ψ+γ detection with J/Ψ→e+e? in pp collisions in the ALICE experiment at LHC

We present Monte Carlo preliminary results about the feasibility to detect the χ _c family in p-p collisions at 14 TeV in the ALICE Central Barrel at CERN LHC. The χ _c1 and χ _c2 were forced to decay in the radiative channel J/Ψ+γ→e ⁺ e ⁻+γ and were merged with a proton-proton non-biased collision. After Monte Carlo transport and simulation of the detector response, the e ⁺, e ⁻ and converted γ were reconstructed and identified in the ALICE ITS, TPC and TRD detectors. Separate signals corresponding to γ from χ _c1 and from χ _c2 were observed. The position and relative weight of the fit to gaussians agreed with the input values within the statistical limits. An erratum to this article can be found at     

Nuclear quadrupole resonance studies of209Bi in Bi4(GeO4)3 and Bi4(SiO4)3

Nuclear quadrupole resonance (NQR) of²⁰⁹Bi has been studied in Bi₄ (GeO₄)₃ and Bi₄ (SiO₄)₃ using a wide band coherence-controlled superregenerative oscillator-detector. All the four allowed (ΔM _I=±1) transitions are observed. In both cases the electric field gradient (EFG) tensor is axially symmetric (η=0.0). The quadrupole coupling constante ² qQ is measured to be 490.8±1 MHz and 470.4±1 MHz respectively. It is pointed out that the purely ionic model is inadequate to understand these results. With the available experimental accuracy and the strength of the applied electric field (∼ 6 KV/cm), no field-induced effects on the NQR spectrum could be observed in the case of Bi₄ (SiO₄)₃.     

Non-steady-state photo-EMF in nanostructured GaN and polypyrrole within porous matrices

We report an experimental investigation of the non-steady-state photoelectromotive force in nanostructured GaN within porous glass and polypyrrole within chrysotile asbestos. The samples are illuminated by an oscillating interference pattern created by two coherent light beams and the alternating current is detected as a response of the material. Dependences of the signal amplitude versus temporal and spatial frequencies, light intensity, and temperature are studied for two wavelengths λ=442 and 532 nm. The conductivity of the GaN composite is measured: σ=(1.1–1.6)×10⁻¹⁰ Ω⁻¹ cm⁻¹ (λ=442 nm, I ₀=0.045–0.19 W/cm², T=293 K) and σ=(3.5–4.6)×10⁻¹⁰ Ω⁻¹ cm⁻¹ (λ=532 nm, I ₀=2.3 W/cm², T=249–388 K). The diffusion length of photocarriers in polypyrrole nanowires is also estimated: L _D=0.18 μm.     

Quark-Antiquark states and their radiative transitions in terms of the spectral integral equation: Bottomonia

In the framework of the spectral integral equation, we consider the states and their radiative transitions. We reconstruct the interaction on the basis of data for the levels of the bottomonium states with J ^PC = 0⁻⁺, 1⁻⁻, 0⁺⁺, 1⁺⁺, 2⁺⁺ as well as the data for the radiative transitions γ (3S) → _γχbJ(2P) and γ(2S) → _γχbJ(1P) with J = 0, 1, 2. We calculate bottomonium levels with the radial quantum numbers n ≤ 6, their wave functions, and corresponding radiative transitions. The ratios Br[_χbJ(2P) → _γγ(2S)]/Br[_χbJ(2P) → _γγ(1S)] for J = 0, 1, 2 are found to be in agreement with data. We determine the component of the photon wave function using the data for the e ⁺ e ⁻ annihilation, e ⁺ e ⁻ → γ(9460), γ(10 023), γ(10 036), γ(10 580), γ(10 865), γ(11 019), and predict partial widths of the two-photon decays ηb0 → γγ, χb0 → γγ, χb2 → γγ for the radial excitation states below the threshold (n ≤ 3). The text was submitted by the authors in English.     

Spin-spin interaction of Ni2+ ions in ZnSiF6·6H2O

The angular dependences of the electron spin resonance spectrum of 1% Ni²⁺ ions in a ZnSiF₆·6H₂O matrix are investigated experimentally at 36 GHz and 4.2 K. Besides the main spectrum of the isolated ion, we observed a spectrum due to interacting pairs of Ni²⁺ ions, located in the first (nn) and second (2n) coordination spheres and coupled by, besides the magnetic dipole-dipole interaction, isotropic exchange: J _nn = (−197±1)×10⁻⁴, J _2nα = (−5±1)×10⁻⁴, and J _2nβ = (3±2)×10⁻⁴ cm⁻¹. Lines due to other isolated Ni²⁺ ions, which have a different initial splitting D, are also present in the spectrum with intensity comparable to the pair spectrum. Low-symmetry distortions of the crystal field are observed, caused by a pair of impurity ions located close to one another. It is shown that the previously proposed interpretation is incorrect. Fiz. Tverd. Tela (St. Petersburg) 41, 1602–1608 (September 1999)     

Cross-correlation effects in NMR spectra of a spin 1/2 scalar coupled to a spin S≥1

In the frame of the density matrix formalism the lineshapes and dynamic frequency shifts in the multiplet structure of a spinI = 1/2 scalar coupled to a quadrupolar nucleus with a spinS ≥ 1 undergoing dipolar (D), quadrupolar (Q) and chemical shift anisotropy (CSA) relaxation are studied. Analytic expressions for the cross-correlation spectral densities J^Q-CSA, J_D-Q, J^D-CSA and also for the real and imaginary Redfield elements of the relaxation matrix were obtained in the general case of noncoincident and nonaxial Q, D, and CSA tensors. On the assumption that CSA and Q interactions are comparable in magnitude the contributions of cross-correlation terms CSA-Q, CSA-D, Q-D in the linewidth and dynamic shifts of the multiplet pattern of a spinI = 1/2 were analyzed in a wide interval of correlation times (10⁻¹²-10⁻⁷ s) for a spin system¹³C-¹¹B and³¹P-⁵⁹Co as an example.     

Temperature dependence of the electric quadrupole interaction at scandium impurities in zirconium and hafnium

The PAC probe⁴⁴Sc was employed to study the magnitude and temperature dependence of the electric quadrupole interaction at the site of the transition metal Sc in the hexagonal host lattices Zr and Hf. In Zr ∼ 100% of the probe atoms were situated on regular lattice sites and a quadrupole interaction frequency of υ_Q=7.8(1)MHz was measured at room temperature. For Hf the fraction of the probe atoms on regular lattice sites was smaller and a damping of the interaction pattern (υ_Q=9.3(5)MHz at 293 K) could not be excluded. The temperature dependence of the electric field gradient in both host lattices was found to be weak.     

The pressure broadening and shift for the J=1−0 line of CH3C14N: Resolved and overlapped hyperfine components

Summary Pressure broadening and shift parameters are measured for theJ=1−0 line of CH₃C¹⁴N at 18.4 GHz, both for the three hyperfine components and for the single line which envelopes the hyperfine components, observed at higher pressures (p≥40 mTorr). In agreement with theoretical predictions, these parameters are the same for all the observed lines: Γ _p = (50 ± 5) MHz/Torr,s=(7±2) MHz/Torr. These values are compared with previous measurements, showing a large variance expecially for the shift parameter. The measured broadening parameter is 40% lower than prediction of the Anderson theory.

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Riassunto Sono stati misurati i parametri di allargamento e spostamento per pressione della rigaJ=1−0 del CH₃C¹⁴N a 18.4 GHz. Tali misure sono state eseguite, sulle tre componenti iperfini e sul loro inviluppo osservato a pressionip≥40 mTorr. In accordo con le previsioni teoriche, questi parametri risultano gli stessi per tutte le righe osservate: Γ _p = (50 ± 5) MHz/Torr,s=(7±2) MHz/Torr. Questi valori sono confrontati con quelli delle precedenti misure che mostrano una considerevole dispersione, specialmente per quanto riguarda il parametro di spostamento. L'allargamento per pressione è risultato piú basso di quello previsto dalla teoria di Anderson di circa il 40%.

     

Cavity enhanced absorption spectroscopy measurements of?pressure-induced broadening and shift coefficients in?the?υ1+υ3 combination band of ammonia

Cavity enhanced absorption spectroscopy is performed using an external cavity diode laser operating around 1516 nm. We demonstrate a sensitivity of 6×10⁻⁸ cm⁻¹ Hz^−1/2 and utilise a simple method to measure pressure-induced broadening and shift coefficients. The broadening and shift coefficients for six gases (helium, neon, argon, xenon, oxygen and nitrogen) have been determined at room temperature for four transitions in the υ ₁+υ ₃ combination band of ammonia. Comparisons of the broadening coefficients with previous work in this region, where it exists, show good agreement. The broadening and shift coefficients of nitrogen and oxygen are also in good agreement with calculated values using the Robert and Bonamy theory. Both the broadening and shift coefficients show a clear trend through the rare gases, which can be explained in terms of the varying magnitude of the long range attractive forces operating between the colliding partners. We also demonstrate the application of the Parmenter–Seaver formalism to estimate the potential well depth of the ammonia dimer from the obtained broadening coefficients. The obtained well depth agrees well with theoretical calculations.     

TDPAC characterization of tin oxides using181Ta

In connection with a general study of the evolution of tin-oxygen thin films, we report here on the hyperfine interactions of¹⁸¹Ta substitutionally replacting tin in the isolated phases SnO and SnO₂. For this purpose, pure SnO pressed powder and a thin SnO₂ film were implanted with¹⁸¹Hf. In both cases, unique quadrupole frequencies were found after thermal annealing treatments. The results indicate that the following hyperfine parameters: υ _Q = 740.6(2.1) MHz, η=0.07(2) and υ _Q = 971.5(1.9) MHz, η=0.72(1) characterize¹⁸¹Ta in SnO and SnO₂, respectively.     

Determination of the helium-4 mass in a Penning trap

The determination of the rotational quadrupole alignment of diatomic molecules via REMPI detection is investigated. In this process a high focal intensity usually increases the detection probability. At high intensities the AC Stark effect may cause a splitting of the normally degenerate m_J sublevels of a rotational state J beyond the spectral width of the exciting radiation. This leads to a selective detection of only certain m_J states with the consequence that deduced alignment factors can be misleading. From the theoretical considerations line profiles are explicitly calculated for dynamic polarizabilities which represent the B ¹Σ⁺ _u←X ¹Σ⁺ _g transition of H₂, in order to fit an experimental (3+1) REMPI spectrum and to predict (1+1') line shapes as a function of laser intensity. It is further shown that the deduced quadrupole alignment factor A ₀ ⁽²⁾ is significantly changed by the second order AC Stark effect when the intensities are chosen high enough to observe asymmetric broadened line profiles. Different combinations of relative linear polarizations of the exciting and ionizing laser beams are discussed. Received 1st August 2000 and Received in final form 2 May 2001     

Quark-antiquark states and their radiative transitions in terms of the spectral integral equation: Charmonia

Earlier by the authors (Yad. Fiz. 70, 68 (2007)), the bƃ states were treated in the framework of the spectral integral equation, together with simultaneous calculations of radiative decays of the considered bottomonia. In the present paper, such a study is carried out for the charmonium states. We reconstruct the interaction in the c-c sector on the basis of the data for the charmonium levels with J _PC = 0⁻⁺, 1⁻⁻, 0⁺⁺, 1⁺⁺, 2⁺⁺, 1⁺⁻ and radiative transitions ψ(2S) → γχ _c0(1P), γχ _c1(1P), γχ _c2(1P), γχ _c(1S) and χ _c0(1P), χ _c1(1P), χ _c2(1P) → γJ/ψ. The c-c levels and their wave functions are calculated for the radial excitations with n ≤ 6. Also, we determine the c-c component of the photon wave function using the e ⁺ e ⁻-annihilation data: e ⁺ e ⁻ → J/ψ(3097), ψ(3686), ψ(3770), ψ(4040), ψ(4160), ψ(4415) and perform the calculations of the partial widths of the two-photon decays for the n = 1 states η _c0(1S), χ _c0(1P), χ _c2(1P) → γγ and n = 2 states η _c0(2S) → γγ, χ _c0(2P) → γγ. We discuss the status of the recently observed c-c states X(3872) and Y(3941): according to our results, the X(3872) can be either χ _c1(2P) or η _c2(1D), while Y(3941) is χ _c2(2P). The text was submitted by the authors in English.     

Defect-acceptor pairs in germanium

The PAC probe¹¹¹In was implanted into intrinsic, n-and p-doped germanium. After removing the radiation damage by thermal annealing the samples were irradiated with different lons to study defect-acceptor pairs by means of the PAC technique. In all samples a high electric field gradient could be observed, characterized by a quadrupole interaction frequency of υ_Q2=415MHz and an axial symmetry (η=0). Some samples show another frequency of υ_Q152.5 MHz and η=0. The results give evidence for an intrinsic defect trapped at the¹¹¹In probe.     

The Ag−In intermetallic compound formation from Ag and In electrodeposited layers observed by PAC

The PAC method was applied to study the intermetallic compound formation at Ag−In interfaces. The electrodeposited Ag−In layers of different Ag: In atomic ratios were prepared and isochronal annealing program was performed. For the comparison the bulk Ag₇₅In₂₅ and Ag₆₆In₃₄ specimens were examined. The Ag₂In and AgIn₂ compounds were detected and the quadrupole hyperfine interaction parameters for¹¹¹In in Ag₂In were measured as υ_Q107.9(3) MHz and η=0.48 (2).