Rotational spectrum of trans-trans diethyl ether in the ground and three excited vibrational states

We report the results of a comprehensive reinvestigation of the rotational spectrum of diethyl ether based on broadband millimetre-wave spectra recently recorded at The Ohio State University and in Warsaw, covering the frequency region 108-366 GHz. The data set for the ground vibrational state of trans-trans diethyl ether has been extended to over 2000 lines and improved spectroscopic constants have been determined. Rotational spectra in the first excited vibrational states of the three lowest vibrational modes of trans-trans-diethyl ether, ν₂₀, ν₃₉, and ν₁₂ have been assigned. The v₂₀ = 1 and v₃₉ = 1 states are near 100 cm⁻¹ in vibrational term value and are coupled by a strong c-axis Coriolis interaction, which gives rise to many spectacular manifestations in the rotational spectrum. All of these effects have been successfully fitted for a dataset comprising over 3000 transitions, leading to precise determination of the energy difference between these states, (ΔE/hc)=10.400222(5) cm⁻¹. A newly developed software package for assignment and analysis of broadband spectra is described and made available.     

Nonequilibriurn discontinuous phase transitions in a fast ionic conductor model: Coexistence and spinodal lines

Two-dimensional lattice-gas models with attractive interactions and particle-conserving hopping dynamics under the influence of a very large external electric field along a principal axis are studied in the case of off-critical densities. We describe the corresponding nonequilibrium first-order phase transitions, evaluate coexistence and spinodal lines, and make some comparisons with experimental observations on fast ionic conductors.See Ref. 1 (henceforth referred to as II) for references.     

Electronic properties of nonhomovalent alloys: A study of the b.c.c. Li−Mg solid solution

Summary The influence of the alloying on the electronic properties of the b.c.c. Li−Mg solid solution has been investigated within the KKR-CPA framework. Such an influence has been studied by computing the band structure, Fermi surface, soft X-ray spectra, residual resistivity and Auger spectra for chosen values of the composition. The theoretical results we obtained are in fair agreement with the surface existing experimental data and support the view that also in ?simple metals? alloys care has to be taken in studying such systems in terms of low-order perturbation approaches.

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Riassunto Sono state studiate varie proprietà elettroniche delle leghe di Li−Mg nell’intervallo di concentrazione in cui questi sistemi cristallizzano nel reticolo b.c.c. In particolare sono state calcolate la struttura a bande, le superfici di Fermi, la resistività residua, gli spettri X ed Auger e si sono confrontati i risultati con i dati sperimentali esistenti. Il buon accordo fra risultati teorici e dati sperimentali indica che, anche per leghe di metalli semplici, gli approcci perturbativi a basso ordine possono essere insufficienti a descrivere il comportamento di tali sistemi.

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Резюме В рамках KKR-CPA исследуется влияние процесса сплавления на электронные свойства объемноцетририованного кубического твердого раствора Li−Mg. Проводятся вычисления зонной структуры, поверхности Ферми, спектров мягкого рентгеновского излучения, остаточного сопротивления и Ож-ye-спектров для выбранных величин состава. Полученные теоретические величины хорошо согласуются с существуюими экспериментальными данными.

     

On the equation of state of classical one-component systems with long-range forces

Several definitions of the pressure are introduced for one-component systems and shown to be nonequivalent in the presence of a rigid neutralizing background. Relations between these pressures are derived for finite and infinite systems; these relations depend on the asymptotic behavior of the force at infinity, with the Coulomb force at the borderline between different properties. It is argued that only one of those definitions is physically acceptable and its properties are discussed in relation to the asymptotic behavior of the force. It is seen in particular that a knowledge of the state of the infinite system is not sufficient to determine its thermodynamic properties. The results are illustrated by some typical examples.For example, for two-dimensional systems with three-dimensional Coulomb interaction see refs. 2–4.     

Induced product representations of extended Cuntz algebras

Let _H be the extended Cuntz algebra over the Hilbert space H. Since its zero grade part _H⁰ is the C^*-inductive limit of B(H^r), we look for some family of representations on an inductive limit of H^r as r. When such construction is shaped according to the structure of _H⁰, von Neumanns notion of a reference sequence of unit vectors for Hilbert infinite tensor products emerges; after a further Rieffel induction step, a class IPR[H] of representations of _H arises. For any two such representations, we describe explicitly their associated intertwiners. Any two representations in IPR[H] are either disjoint or unitarily equivalent. Actions of the group by translation on sequences of unit vectors are involved, as well as the ideals of .     

Temperature dependence of the linewidth of the first-order Raman spectra for MnF2 crystal

The first-order Raman spectra ofE _gandA _1g modes in MnF₂ crystal were measured at temperatures from 4.2 to 563 K, and the values of the linewidths obtained. The temperature dependence of the linewidths was analyzed by the phonon dispersion curves based on the rigid ion model, and the result showed that it was caused approximately by the cubic anharmonic term in crystal potential energy.     

Spontaneous translation symmetry breakdown for quantum lattice systems

We study the set of equilibrium states for quantum lattice states in the presence of a translation symmetry of the model. We derive a characterization of the spontaneous breaking of this symmetry, i.e., the decomposition of an invariant equilibrium state into a mixture of noninvariant equilibrium states, in terms of the separability in mean energy of these states for a class of perturbed dynamics.     

Predictions of γ(4S)→h_b(1P,2P)π^+π^- transitions

We study the contributions of intermediate bottomonium-like Zb states and the bottom meson loops in the heavy quark spin flip transitionsγ(4 S)→hb(1 P,2 P)π+π-.Depending on the constructive or destructive interferences between the Zb-exchange and the bottom meson loops mechanisms,we predict two possible branching ratios for each process:BRγ(4 S)→hb(1 P)π+π-≈(1.20.40.8×10^-6)or(0.5-0.20.5×10^-6),and BRγ(4 S)→(2 P)π+π-≈(7.1-1.1+1.7×10^-10)or(2.4-0.10.2×10^-10)).The contribution of the bottom meson loops is found to be considerably larger than that of the Zbexchange in the T(4 S)→hb(1 P)ππtransitions,while its decay rates are not comparable to those of heavy quark spin conservedγ(4 S)→γ(1 S,2 S)ππprocesses.We also predict the contribution of the charm meson loops in the branch fractions ofΨ(3 S,4 S)→hc(1 P)ππ.     

Brownian motion in a fluid in elongational flow

Brownian motion of a spherical particle in stationary elongational flow is studied. We derive the Langevin equation together with the fluctuation-dissipation theorem for the particle from nonequilibrium fluctuating hydrodynamics to linear order in the elongation-rate-dependent inverse penetration depths. We then analyze how the velocity autocorrelation function as well as the mean square displacement are modified by the elongational flow. We find that for times small compared to the inverse elongation rate the behavior is similar to that found in the absence of the elongational flow. Upon approaching times comparable to the inverse elongation rate the behavior changes and one passes into a time domain where it becomes fundamentally different. In particular, we discuss the modification of thet ^–3/2 long-time tail of the velocity autocorrelation function and comment on the resulting contribution to the mean square displacement. The possibility of defining a diffusion coefficient in both time domains is discussed.     

观测有效相干长度及TC周期性的全息法

本文根据J.Upatinieks的椭圆等光程原理,提出了一种现场观测多纵模激光有效相干长度及其TC周期性的全息法.介绍了基本原理与方法,给出了相应的实验结果.