Evidence of anomalous multiplet line shapes in optically thick,laser-produced plasmas

We report observations of anomalous line shapes for the transitions 2p?3d (²P?²D) emitted by the Li-like ions N(V), O(VI), F(VII) in laser-produced plasmas. These transitions are normally doublets but show completely different characteristics (e.g., triplet structures or invension of two-component intensity ratios) in the plasmas. The observed line profiles are accounted for in terms of opacity and Doppler effect produced by plasma expansion. This interpretation is independent of the particular transition involved, i.e., multiplet structures can generate more complicated features with various unexpected new components, anomalous intensity ratios, etc.     

Core-polarization and open-shell effects in E6 transitions

The problem of isomeric E6 transitions recently measured in the fp shell is investigated. In the shell model these E6 decay rates require negative proton polarization charges and are quite anomalous in the context of usually enhanced E2 and E4 transitions. We demonstrate that usual core-polarization mechanisms cannot be invoked to explain the data and that the quadrupole deformations of the open shell that must be taken into account are instrumental in yielding negative P₆ moments.     

Limits on anomalous top couplings from Z pole physics

We obtain constraints on possible anomalous interactions of the top quark with the electroweak vector bosons arising from the precision measurements at the Z pole. In the framework of SU(2)_L ⊗ U(1)_Y chiral Lagrangians, we examine all effective CP-conserving operators of dimension five which induce fermionic currents involving the top quark. We constrain the magnitudes of these anomalous interactions by evaluating their one-loop contributions to the Z pole physics. Our analysis shows that the operators that contribute to the LEP observables get bounds close to the theoretical expectation for their anomalous couplings. We also show that those which break the SU(2)_C custodial symmetry are more strongly bounded.     

Phase changes in cubic rare earth crystals

An explanation is offered of the structural transitions and magnetic orderings in the cubic rare earth compounds LnX with particular emphasis on the anomalous spin arrangements observed in HoP, DyP and DyAs and in ErSb and ErP.     

Tunneling of 6<Emphasis Type="Italic">s</Emphasis><Superscript><Emphasis Type="Italic">2</Emphasis></Superscript> electrons in PbO and Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>: XANES spectroscopy and DFT calculations

The results of XANES spectroscopy and DFT calculations are evidence for the occurrence of anomalous 2p_2/3→6s_1/2 electronic transitions in lead(II) and bismuth(III) oxides. The observed transitions may be due to the tunneling of outer 6s² electrons.     

Anomalous states of the structure of (NH4)2SO4 crystals in the temperature range 4.2–300 K

Crystals of the (NH₄)₂SO₄ ammonium sulfate are studied using x-ray diffractometry. It is revealed that the temperature dependence of the lattice parameters exhibits an anomalous behavior, namely, a global hysteresis, and an anomalous increase in the lattice parameter a and the unit cell volume at temperatures below the ferroelectric phase transition point (T _c=223 K). The series of superstructure reflections observed corresponds to an incommensurate composite structure. Analysis of the temperature behavior of the mismatch parameters for the matrix (host) and superstructure (guest) lattices demonstrates that the (NH₄)₂SO₄ compound undergoes a number of phase transitions, including a transition to a three-dimensionally incommensurate composite phase and transitions to commensurate (along one of the crystallographic directions) composite phases.     

Angular Correlations in Associated Production of Single Top and Higgs with and without Anomalous W t b Couplings

We study the angular correlation and the amount of top quark polarization in the production of a higgs boson in association with a single top quark in the t?channel at the LHC. We also study the effect of anomalous W t b couplings on the angular correlation and on the production cross section of the process. The cross section and angular correlation is almost insensitive to the variation of the Higgs boson mass within 3 GeV. The robustness of the angular correlation against the center-of-mass energy of the proton-proton collision, the variation of parton distribution functions, and the change of factorization scale is investigated. The sensitivity of this process to the anomalous couplings is examined.     

Continuum fluids with a discontinuity in the pressure

A class of one-dimensional continuum fluid models is defined in which classical particles interact through translationally invariant, strongly tempered manybody potentials meeting conditions sufficient to ensure a proper thermodynamic limit. However, an exact analysis demonstrates that for certain ranges of parameter values the pressure versus density isotherms arediscontinuous. The basic models also entail discontinuous temperature versus configurational entropy isobars but extended models are described which exhibit either type of anomaly alone and various unobserved but thermodynamically allowed, anomalous types of first-order transitions.     

The Zeeman effect in doublet-quartet transitions in orthorhombic rotating molecules

Theoretical predictions on the effect of magnetic fields of variable strength on the rotational structure of doublet-quartet transitions in orthorhombic near symmetric top molecules are reported, with the assistance of computer simulations of line profiles. Low-field profiles are discussed, and it is shown that low-field linewidths are approximately equal to 2gβH|ΔJ ? ΔN| for transitions between states of any spin multiplicity. In a high field, transitions allowed by direct spin-orbit contamination of the combining states give rise to three lines with ΔM_s = 0, ±1, whereas two additional lines, with ΔM_s = ±2, are found if the combining states are appreciably contaminated also by indirect coupling to the active states, through intermediate levels. Computed Zeeman profiles are reported and discussed for several typical cases, with emphasis on the effects of different light polarizations. Prospectives of applicability are briefly outlined.     

The torsion-rotation spectrum of perchloric acid, HClO4

The rotational spectrum of HClO₄ has been observed in selected regions between 51.7 and 870 GHz. The molecule is a near spherical rotor with a moderately low barrier to internal rotation. The spectrum is characterized by strong μ_a, R-branch groupings with B + C = 5276.78 MHz. Although there are no E torsional states, the R-branches show three distinct groups of lines. There is a relatively tight cluster of symmetric rotor like transitions with K = 3n, a rather regular progression of transitions with K = 3n + 2 to high frequency and a less regular group of transitions with K = 3n + 1 to low frequency. Because the molecule is nearly spherical, the energy as a function of K is dominated by the K dependent solutions of the Mathieu equation. This unusual energy level distribution gives rise to numerous anomalous splittings and shifts due to avoided crossings within the K stacks as well as widely scattered μ_b transitions. The fitting procedure will be described and the effective parameters will be presented. Rotational transitions of excited torsional states at and above the top of the barrier and the v_t = 2-0 far infrared spectrum have been assigned. The dipole moment and the quadrupole coupling constants have been determined. Structural implications will be discussed.     

Temperature dependence of interband transitions and exchange splitting in nickel

Interband transitions of Ni have been studied as a function of temperature by observing energy losses of low energy electrons reflected from a Ni(100) surface. A threshold is found at E_g ～ 0.15 eV and interpreted as the onset of X^↑₅ → X^↓₂ transitions. The threshold remains unchanged for temperatures up to 900 K. The loss continuum below E_g exhibits an anomalous increase with temperature with a discontinuity in the slope at T ～ 1.2 T_c.     

The origin of anomalous temperature dependences of intensities of spin-forbidden d-d transitions in octahedral complexes

It is shown that anomalous temperature dependences of intensities of spin-forbidden d-d transitions, observed in octahedral magnetically-ordering complexes in a paramagnetic phase and in particular in hexagonal RbMnCl₃, investigated by the authors, can be accounted for by a pair-vibrational mechanism, which represents two simultaneous events: breaking of selection rules for spin during pair absorption by exchange coupled ions and breaking of those for parity during an ordinary electronic transition in one of the ions of the pair due to excitation of odd-parity vibrations.     

Anomalous behaviour of the Urbach edge and phase transitions in TlGaSe2

The long-wavelength tail of the optical absorption in TlGaSe₂, crystals at α=30−150cm^-1 is shown to obey Urbach's rule in the temperature range 4.2–294°K. The anomalous behaviour of the parameters of this rule suggests the presence of two phase transitions in TlGaSe₂ at 246°K and 101°K beside the known phase transitions at 120°K and 107°K. The presence of phase transitions in TlGaSe₂ at 246°K and 101°K is also confirmed by means of the heat capacity measurement.     

Rotational transitions in degenerate vibrational states of C3v symmetric top molecules,with application to CH3C15N

General algebraic expressions for the vibration-rotation energy levels and the associated rotational transitions of C_3v symmetric top molecules are developed. These expressions are presented in a convenient form for analysing the spectra of a molecule with any degree of excitation of a degenerate vibrational mode and have been applied to the spectrum of CH₃C¹⁵N.     

On the octupole excitation in236U

Measurements of theK,L _I,L _II andM _I conversion lines of the 687.7 keV transition in²³⁶U are evaluated within the electron penetration formalism. The spin-parity assignment of the octupole bandhead is found to be 1^? in accordance with reaction data, and an assignment of 2^? to the 687.7 keV state is ruled out. The penetration matrix element ∥η∥ has the value of 13.5 for theK-shell and increases slightly for higher main shells. An estimate of the anomalous amplitudes is compared with values reported for transitions in the odd even actinide nuclei. Furthermore electron conversion data for the 1^?→2⁺ and 1^?→4⁺ transitions are given. Radioactivity²³⁶U from²³⁵U(n,e ^?); measured: conversion electron decay; deduced: conversion coefficients fromK, L andM shells; evaluated: dynamic matrix elements.     

Anomalous heating rate effect in thermoluminescence intensity using a simplified semi-localized transition (SLT) model

During thermoluminescence (TL) measurements carried out with different heating rates, one expects the total number of emitted photons to be constant. However, for many luminescence materials one observes a decreased intensity of luminescence at elevated temperatures, due to the presence of the well-known phenomenon of thermal quenching. Recent experimental work on the dosimetric material YPO₄ double doped with lanthanides demonstrated the exact opposite behavior, in which the total luminescence intensity increases with the heating rate during the TL experiments. This anomalous TL behavior was recently explained by using the Mandowski model of semi-localized transitions (SLTs). In this paper it is shown that this anomalous heating rate or “anti-quenching” phenomenon can also be described by using a simplified SLT model of TL with approximated kinetic equations. The simulated glow curves show that as the probability of the non-radiative processes increases, the anomalous heating rate effect becomes dominant. The dependence of the anomalous heating rate effect on the values of the kinetic parameters in the model is examined by allowing random variations of the parameters in the model, within wide ranges of physically reasonable values covering several orders of magnitude. It is shown by simulation that the variable heating rate method can systematically underestimate the value of the activation energy E, while by contrast the initial rise method of analysis almost always yields the correct E value. These simulated results are discussed in relation to recent experimental work on the double doped dosimetric material YPO₄.     

Correlation of acoustic and thermal anomalies in ferroelectric crystals

The Pippard-Janovec relations are derived for correlating the anomalous elastic coefficient and the anomalous specific heat near the phase transitions of ferroelectric crystals. These relations are verified in the case of ferroelectric triglycine selenate crystal.     

Probe of the Wtb coupling in t \bar{t} pair production at linear colliders

The Wtb vertex can be probed on future colliders in the processes of single top production (LHC, pp mode, NLC, mode) and of top pair production (NLC, mode). We analyze observables sensitive to anomalous Wtb couplings in the top pair production process of collisions. In particular, forward–backward and spin–spin asymmetries of the top decay products and the asymmetry of the lepton energy spectrum are considered. Possible bounds on anomalous couplings obtained are competitive to those expected from the upgraded Tevatron and LHC. The validity of the infinitely small width approximation for the three-body top decay is also studied in detail. Received: 20 January 2000 / Revised version: 12 April 2000 / Published online: 18 May 2000     

A study of 75Se by neutron capture and the SU(3)-SU(5) transition in the quadrupole-phonon representation

The γ and e^? spectra following thermal neutron capture in ⁷⁴Se were studied with curved-crystal, β, and pair spectrometers. Precise energies have been obtained for the transitions and levels at low energies. Two primary E2 transitions were found. The neutron separation energy for ⁷⁵Se was determined as 8027.6 keV. Precise γ-energies following the electron capture decay of ⁷⁵Se were also measured, resulting in precise level energies in ⁷⁵As. The calculation of the energy levels in ⁷⁵Se has been performed in the SU(6) particle-vibrational model (PTQM) and 27 theoretical states have been tentatively assigned to the experimental levels. The spectrum of the core nucleus ⁷⁴Se has been calculated in the SU(6) quadrupolephonon model (TQM). The structure of theoretical states, the relation to SU(3) and SU(5) limits, and potential energy surface are discussed. The E2, M1 and E1 transitions have been calculated in PTQM and compared to the experiment. Also, an overview is presented of theoretical explanations of the I = j, j?1, j?2 anomalous triplet emphasizing the rule with shell-model classification corrected for quadrupole phonons.