Rotation-vibrational states of H3+ and the adiabatic approximation

We discuss recent progress in the calculation and identification of rotation-vibrational states of H3+ at intermediate energies up to 13,000 cm(-1). Our calculations are based on the potential energy surface of Cencek et al. which is of sub-microhartree accuracy. As this surface includes diagonal adiabatic and relativistic corrections to the fixed nuclei electronic energies, the remaining discrepancies between our calculated and experimental data should be due to the neglect of non-adiabatic coupling to excited electronic states in the calculations. To account for this, our calculated energy values were adjusted empirically by a simple correction formula. Based on our understanding of the adiabatic approximation, we suggest two new approaches to account for the off-diagonal adiabatic correction, which should work; however, they have not been tested yet for H3+. Theoretical predictions made for the above-barrier energy region of recent experimental interest are accurate to 0.35 cm(-1) or better.     

The adiabatic approximation and Fröhlich model in the theory of metals

Based on the adiabatic expansion for metals, a method is developed whereby it is possible to compute the nonadiabatic corrections to the energy of any order by standard perturbation theory and diagram techniques. It turns out that in addition to the Fröhlich one-phonon Hamiltonian the many-phonon Hamiltonians also play a significant role in the theory of metals. Inasmuch as the ground state of the system corresponds to adiabatic perturbation theory, the largest correction to the energy and phonon frequency is of the order(m/M) ^1/2, as opposed to the results deduced from the Fröhlich Hamiltonian. The expression for the ordinary self-energy contribution differs substantially from its expression in the Fröhlich model, and the equation for the pairing self-energy contribution coincides up to terms of order(m/M) ^1/2 with the corresponding equation in the Fröhlich model. The expression for the critical temperature is discussed.     

Electron and spin transport in adiabatic quantum pump based on armchair graphene nanoribbons

The phenomenon of adiabatic quantum pump in double-barrier structures based on armchair graphene nanoribbons has been theoretically analyzed within the framework of the tight binding approximation. An analytical expression for a bilinear response is obtained that is valid at small Fermi energies. Using the effect of proximity to a ferromagnetic dielectric, it is possible to obtain both electron and pure spin currents. Dependences of the generated electron and spin currents on the Fermi energy have been numerically calculated. The validity of the adiabatic approximation is assessed based on the dwell time for electron travelling through the system.     

Profiles of nonlinear motion of magnetization in superfluid 3He. II. Nonlinear parallel ringing in adiabatic perturbation approximation

The Ambegaokar-Levy theory of the relaxation of the ringing energy of magnetization in superfluid ³He-A is reformulated and extended to ³He-B. Ringing profiles with dissipative effects are calculated by combining the solution of the relaxation equation and free ringing profiles.     

Generalized definition of the adiabatic exponent

A generalized definition of the adiabatic exponent, which holds for ideal and real gases, is investigated. The generalized definition makes it possible to apply a number of formulas of engineering thermodynamics and gas dynamics to a real gas, using a parameter called the ideal temperature.     

On the adiabatic theorem in quantum mechanics

The adiabatic and postadiabatic approximations, as well as the adiabatic and nonstationary perturbation theories, are constructed using a canonical averaging method under the assumptions which are more general than those used in the existing theories. An asymptotic evaluation of the proximity of rigorous and approximate solutions is performed.     

On the calculation of adiabatic processes in real gases

Means of calculating the final temperature of an isoentropic process, and also the temperature drops, are discussed. It is shown that in calculations of adiabatic processes it is advisable in some cases to use the proposed adiabatic exponent m.     

Design of the PIXIE adiabatic demagnetization refrigerators

The Primordial Inflation Explorer (PIXIE) is a proposed mission to densely map the polarization of the cosmic microwave background. It will operate in a scanning mode from a sun-synchronous orbit, using low temperature detectors (at 0.1 K) and located inside a telescope that is cooled to approximately 2.73 K – to match the background temperature. A mechanical cryocooler operating at 4.5 K establishes a low base temperature from which two adiabatic demagnetization refrigerator (ADR) assemblies will cool the telescope and detectors. To achieve continuous scanning capability, the ADRs must operate continuously. Complicating the design are two factors: (1) the need to systematically vary the temperature of various telescope components in order to separate the small polarization signal variations from those that may arise from temperature drifts and changing gradients within the telescope, and (2) the orbital and monthly variations in lunar irradiance into the telescope barrels. These factors require the telescope ADR to reject quasi-continuous heat loads of 2–3 mW, while maintaining a peak heat reject rate of less than 12 mW. The detector heat load at 0.1 K is comparatively small at 1–2 μW. This paper will describe the 3-stage and 2-stage continuous ADRs that will be used to meet the cooling power and temperature stability requirements of the PIXIE detectors and telescope.     

On the calculation of the neutron adiabatic spin-flipper

The theoretical treatment of the neutron spin-flipper based on adiabatic passage through a magnetic resonance is carried out. An equation of neutron spin motion with constant adiabatic parameter has been analytically solved and the relation of this parameter with flipping efficiency has been determined. Numerical calculations for magnetic fields of different forms have been performed and quantitative estimations of the adiabatic parameter for spin rotation to 90° and 180° are presented.     

Optimization of the method of scanning adiabatic calorimetry

The problem of optimizing the measurements of the temperature dependence of heat capacity, thermal effects, and thermal conductivity in a scanning calorimeter is examined.Translated from Inzhenerno-Fizicheski Zhurnal, Vol. 41, No. 1, pp. 129–135, July, 1981.     

On the role of strain gradients in adiabatic shear banding

Summary The effect of higher order strain gradients on adiabatic shear banding is investigated by considering the simple shearing of a heat conducting thermoviscoplastic material with a gradient-dependent flow stress. The competition between the gradient-dependent plastic flow and heat conduction and their influence on the shear band width and structure are examined. Two internal length scales, i.e., the deformation internal length and the thermal internal length, are incorporated into the linear stability analysis, which shows that the band width size scales either with the square root of the strain gradient coefficient (in the absence of heat conduction) or the thermal conductivity (in the absence of strain gradients), respectively. The numerical computation for the nonlinear problem reveals that the diffusive effect of the strain gradient is much stronger than that of the heat conduction and dictates the constitutive response of the material in the postlocalization regime, and shows that the deformation length scale is much larger than the termal length scale. The band width predicted by the gradient theory agrees reasonably well with the experimental observations found in the literature.     

Self-field degradation effect in adiabatic conditions

In multifilamentary superconducting composites mutual inductance between the filament give rise to self-field degradation effects. In this paper radial current density redistribution is first examined taking into account the spiral field effect. Then the limits of stability in adiabatic conditions imposed on these composites by self-field degradation are examined and the results of experiments carried out on short samples and non-inductive coils under adiabatic conditions discussed.     

Influence of adiabatic conditions on the losses in composite superconductors

The losses in composite multifilamentary superconductors during a pulse of a transverse magnetic field under adiabatic conditions have been studied. A considerable difference in value and character of the loss dependences under adiabatic conditions, as compared to those under isothermal conditions, was found. The influence of various factors and conductor parameters on the losses was investigated.     

On variants of the neutron adiabatic spin flipper

New variants of the neutron broadband adiabatic spin flipper are proposed and compared.     

On the adiabatic perturbation theory for metals

The diagram technique developed in an earlier paper for the adiabatic theory of perturbations in normal and superconducting metals is reduced to completely standard form. It is shown on the basis of the adiabatic perturbation theory that the matrix element in the theory of conduction in metals has a unique form consistent with the rigid-ion model.     

Breakdown Initiation in Water with the Aid of Bubbles

The breakdown initiation in water is investigated using artificially produced long-lived microbubbles 40–100 m in size obtained with the aid of a pulse-heated wire electrode. In all cases, the discharge is initiated in a bubble, with the prebreakdown time in the presence of a bubble being much shorter than in its absence. In the case of a discharge from the anode, three series of shock waves are observed in the electrode region, associated with the ignition of the discharge, the propagation of a supersonic streamer, and the release of energy when the streamer closes the interelectrode gap. In the case of cathode breakdown initiation, disturbances develop on the bubble surface in the form of a bush propagating at a subsonic speed in the direction of the opposite electrode. The possibilities of streamer and multiavalanche mechanisms of the breakdown of microbubbles are discussed.     

Laser-Induced Breakdown in Liquid Helium

We report on experiments in which focused laser light is used to induce optical breakdown in liquid helium-4. The threshold intensity has been measured over the temperature range from 1.1 to 2.8 K with light of wavelength 1064 nm. In addition to the measurement of the threshold, we have performed experiments to study how the breakdown from one pulse modifies the probability that a subsequent pulse will result in breakdown.