利用超球势曲线分析正电子与氦原子体系中的共振态

超球势曲线用来分析正电子氦原子体系中的共振态。利用插值方法得到交叉的势曲线,然后求解超球薛定谔方程。计算结果表明处于-0.07922 a.u.的共振是与Ps(n=2)态相联的,而处于-0.06888 a.u.的共振是与He（1s3s）态相关。     

A numerical investigation of occurrence conditions and line broadening effects for a rapid adiabatic passage process

Rapid adiabatic passage processes are discussed for a two-level system. Attention is paid to the transition from Rabi oscillations to adiabatic following. For the latter case the absence of power broadening is demonstrated. Effects of two-laser fields are investigated, and applied to molecular beams crossing the laser radiation near to an intracavity focus.     

Rapid adiabatic passage without level crossing

We present a method for achieving complete population transfer in a two-state quantum system via adiabatic time evolution in which, contrary to conventional rapid adiabatic passage produced by chirped pulses, there occurs no crossing of diabatic energy curves: there is no sign change of the detuning. Instead, we use structured pulses, in which, in addition to satisfying conditions for adiabatic evolution, there occurs a sign change of the Rabi frequency when the detuning is zero. We present simulations that offer simple geometrical interpretation of the two-dimensional motion of the Bloch vector for this system, illustrating how both complete population inversion and complete population return occur for different choices of structured pulses.     

Control of diabatic versus adiabatic field dissociation in a heavy Rydberg system

A novel phenomenon is observed in the dynamics of laser-prepared coherent wave packets, bound by the Coulombic 1/r potential of an ion-pair system. After exciting weakly bound (approximately 3 meV) H(+)(-) wave packets in a Stark field, and permitting them to evolve in time, control of field dissociation via adiabatic and diabatic routes is demonstrated by applying delayed pulsed-electric fields, involving a zero-field crossing. Control manifests itself through the production of ions from each pathway at a different instant in time. This phenomenon is applied to map the oscillatory behavior of an angular momentum wave packet in a heavy Rydberg system. The characteristic frequencies of the observed Stark oscillations verify predicted mass-scaling laws for heavy Rydberg systems.     

Studies of the nuclear inertia in fission and heavy-ion reactions

On the basis of the non-self-consistent cranking model we study some aspects of the nuclear inertia of interest in fission and heavy-ion reactions. First, we consider in the adiabatic limit the inertia for a doubly closed-shell nucleus in a deformed spheroidal harmonic-oscillator single-particle potential plus a small perturbation. When expressed in terms of a coordinate that describes the deformation of the nuclear matter distribution, the inertia for small oscillations about a spherical shape is exactly equal to the incompressible, irrotational value. For large distortions it deviates from the incompressible, irrotational value by up to about ±1 % away from level crossings. Second, in order to study the dependence of the inertia upon a level crossing, we consider in detail two levels of the above system. This is done both in the adiabatic limit and for large collective velocities. At level crossings the adiabatic inertia relative to the deformation of the matter distribution diverges as 1/|ΔV|, where |ΔV| is the magnitude of the perturbation. However, for large collective velocities the contribution to the inertia from a level crossing is less than 4|ΔV|r²_m, where r_m is the collective velocity of the matter distribution. Although we have not considered the effect of large velocities on the remaining levels of the many-body system or the effect of a statistical ensemble of states, some of our results suggest that for high excitation energies and moderately large collective velocities the nuclear inertia approaches approximately the irrotational value.     

Exact triple-avoided-crossing resolution for three-body molecular systems

The hyperradial-adiabatic approach is used to study a region of localized triple-avoided crossing. A three-by-three orthogonal transformation involving a system of strongly coupled hyperradial Schrödinger equations is developed, leading to an exact coherent compensation of all peaks in the matrix elements of adiabatic corrections. In other words, the closure relation between adiabatic corrections matricesH+Q ²=0, which formally holds for a complete basis set, is nicely saturated by three strongly interacting states. One may suggest this to be a property of the hyperradial-adiabatic basis.     

Possibility of non‐adiabatic level crossing by DFT study of tautomerism and potential energy surfaces in of 3‐hydroxy‐5‐(pyrimidin‐2‐yl)‐2H‐pyrrol‐2‐one and its tautomer

3‐Hydroxy‐5‐(pyrimidin‐2‐yl)‐2H‐pyrrol‐2‐one (HYPO, T1) and 2‐hydroxy‐5‐(pyrimidine‐2‐yl)‐3H‐pyrrole‐3‐one (HYPO, T2) have designed in this research to study potential energy curves for their dynamic motions and possibility of crossing between levels. Study of tautomerism shows that T1 tautomer is more stable than T2 (about 5.83 kJ/mol). Dynamic study of possible motions show rate constants (highest possible) equal to 8.82 M/s for tautomerism, 1.70 × 10⁹ M/s for relative rotation of ring (rr) and 3.67 × 10⁶ M/s for rotation of OH bond (br). Moreover, variations of orbital populations, NBO charges, hybridations, and acceptor–donor interactions in IRC steps have been investigated to study the possibility of non‐adiabatic crossing between tautomerism and ring rotation potential energy curves. The data showed that in spite of the fact that these two potentials share three common points, these two potential curves cannot have non‐adiabatic crossing because of different symmetries and a large difference between their barrier energies. Copyright © 2010 John Wiley & Sons, Ltd.     

Butterfly hysteresis loop at nonzero bias field in antiferromagnetic molecular rings: cooling by adiabatic magnetization

At low temperatures, the magnetization of the molecular ferric wheel NaFe6 exhibits a step at a critical field B(c) due to a field-induced level crossing. By means of high-field torque magnetometry we observed a hysteretic behavior at the level crossing with a characteristic butterfly shape which is analyzed in terms of a dissipative two-level model. Several unusual features were found. The nonzero bias field of the level crossing suggests the possibility of cooling by adiabatic magnetization.     

On the luminescence quenching of F centres in alkali halides

Non-radiative transitions from the excited state of F center to the ground state occur very efficiently around and above, over a rather large interval of energy, the crossing point of the two adiabatic potential energy curves. Taking this effect into account the criterion for luminescence quenching originally proposed by Dexter et al. is re-examined. The luminescence quantum efficiency is estimated for those alkali halides in which the luminescence is weak, and the results are in general accord with experiment. The border-line case of NaCl is also explained.     

Comparison between static and adiabatic coupling mechanisms for nonradiative multiphonon transitions in semiclassical approximation I. Tunnelling at small relaxation

Basic equations of the perturbational theory of nonradiative multiphonon transitions are reformulated in semiclassical approximation. They are specialized for the mechanisms of static (diabatic) and adiabatic coupling corresponding to the polar alternatives of crossing versus non-crossing oscillator potentials in a two-level-one-mode system. Tunnelling rates are calculated on the basis of contour integrals in the complex co-ordinate plane. These rates for static coupling are proportional to the square of the off-diagonal electron-oscillator interaction as commonly expected. For the alternative of adiabatic coupling we have obtained a non-monotonous (oscillating) pre-exponential transition rate factor. This unfamiliar result is based on a certain beyondnon-Condon procedure consisting in a consequent observation both of the familiarnon-Condon effect represented by the Lorentz function behaviour of the non-adiabaticity term and the associatedavoided- crossing (hyperbolic) behaviour of adiabatic potentials in the classical transition region. Present results confirm both the general non-equivalence of both alternative coupling mechanisms and a certain asymptotic approach between mechanism-specific tunnelling rates at small off-diagonal interactions.     

Does adiabatic quantum optimization fail for NP-complete problems?

It has been recently argued that adiabatic quantum optimization would fail in solving NP-complete problems because of the occurrence of exponentially small gaps due to crossing of local minima of the final Hamiltonian with its global minimum near the end of the adiabatic evolution. Using perturbation expansion, we analytically show that for the NP-hard problem known as maximum independent set, there always exist adiabatic paths along which no such crossings occur. Therefore, in order to prove that adiabatic quantum optimization fails for any NP-complete problem, one must prove that it is impossible to find any such path in polynomial time.     

Jump of the adiabatic invariant at a separatrix crossing: Degenerate cases

An expression for the quasi-random jump of the adiabatic invariant at a separatrix crossing is obtained for a slow-fast Hamiltonian system with two degrees of freedom in the case when the separatrix passes through a degenerate saddle point in the phase plane of the fast variables. The general case with an arbitrary degree of degeneracy was considered, and this degree is assumed to remain fixed in the process of evolution of the slow variables. The typical value of the jump is larger than in the non-degenerate case studied earlier. Though strongly degenerate, such a setting can be relevant for physical problems. The influence of the asymmetry of a phase portrait on the magnitude of adiabatic invariant jumps was considered as well. An example of this kind is studied, namely the motion of ions in current sheets with complex inner structure.     

Quasiadiabatic, nonfocusing transition-energy crossing

A quasiadiabatic nonfocusing transition-energy crossing is proposed for suppressing any nonadiabatic and undesired features in a longitudinally separated function-type accelerator, in which particles are confined by an radio-frequency voltage with an adiabatic reduction of the amplitude and accelerated by a step voltage. This new method has been examined, both theoretically and experimentally.     

Theoretical study of the LiNa molecule beyond the Born–Oppenheimer approximation: adiabatic and diabatic potential energy curves,radial coupling,adiabatic correction,dipole moments and vibrational levels

ABSTRACT

The adiabatic potential energy curves for ground and many excited states of ^{1, 3}Σ⁺, ^1,3Π, ^1,3Δ symmetries of the LiNa molecule have been performed. We have used an ab initio approach based on non-empirical pseudopotentials, parameterised l-dependent polarisation potentials and full configuration interaction calculations. In addition, the adiabatic potential energy curves determined in our previous work [Mabrouk and Berriche, J. Phys. B: At. Mol. Opt. Phys. 41, 155101 (2008).] are corrected by using a diabatisation procedure, based on the effective Hamiltonian theory and an effective metric. The diabatic permanent moments for first 10 ¹Σ⁺ electronic states show linear behaviours, especially at intermediate and large distance. The transition dipole moment between neighbour states has revealed many peaks located around the avoided crossing positions. The radial coupling between the adiabatic states was calculated using the Hellmann-Feynman formula and numerical differentiation of the rotation matrix. The first and the second derivatives revealed many peaks, associated to neutral-neutral and ionic-neutral crossings. Furthermore, the radial coupling is used to evaluate the adiabatic correction, which is found to be of an order of tens and hundreds of cm^?1, especially of higher excited states. In addition, we have determined the vibrational level spacing for all studied states.     

Primordial fluctuations and non-Gaussianities in multifield Dirac-Born-Infeld inflation

We study Dirac-Born-Infeld inflation models with multiple scalar fields. We show that the adiabatic and entropy modes propagate with a common effective sound speed and are thus amplified at the sound horizon crossing. In the small sound speed limit, we find that the amplitude of the entropy modes is much higher than that of the adiabatic modes. We show that this could strongly affect the observable curvature power spectrum as well as the amplitude of non-Gaussianities, although their shape remains as in the single-field Dirac-Born-Infeld case.     

Predissociation and the vibrational spectrum of molecular oxygen in an intense laser field. A Schumann-Runge band interval

The probabilities of predissociation and vibronic transitions between the states of the oxygen molecule in the Schumann-Runge band in the presence of a strong laser field are examined. The interaction of the molecule with the laser field is described using the rotating wave approximation. The predissociation probabilities for the avoided crossing of two adiabatic molecular terms are calculated within the framework of the Landau-Zener model. The energies of the vibrational states in the laser field are determined by diagonalization of the adiabatic Hamiltonian in the harmonic oscillator basis set. The predissociation thresholds are determined and the Franck-Condon factors are calculated as functions of the frequency and intensity of the external electromagnetic field.     

Coherent control of interacting electrons in quantum dots via navigation in the energy spectrum

Quantum control of the wave function of two interacting electrons confined in quasi-one-dimensional double-well semiconductor structures is demonstrated. The control strategies are based on the knowledge of the energy spectrum as a function of an external uniform electric field. When two low-lying levels have an avoided crossing, our system behaves dynamically to a large extent as a two-level system. This characteristic is exploited to implement coherent control strategies based on slow (adiabatic passage) and rapid (diabatic Landau-Zener transition) changes of the external field. We apply this method to reach desired target states that lie far in the spectrum from the initial state.     

Acoustic topological adiabatic passage via a level crossing

Stimulated adiabatic passage has been extensively studied to achieve robust and selective population transfer in quantum systems. Recently, the quantum-classic analogy has been rapidly developing and can be considered responsible for the implementation of the adiabatic transfer of sound energy in cavity chain systems. In this article, we investigate the adiabatic transfer of sound energy between two topological end states in the Su-Schrieffer-Heeger(SSH) cavity chain, which can be considered to be the acoustic analog of the quantum chirped-pulse excitation. The topological adiabatic passage in SSH cavity chain has two categories. When the single-cavity resonance frequencies on the sublattices A and B in the SSH cavity chain do not switch their spectrum positions, the topologically protected adiabatic evolution results in the returning passage of the sound excited in one end cavity. When a level crossing with single-cavity resonance frequencies on the sublattices A and B exhibits switch in the frequency spectrum, acoustic energy is observed to be topologically pumped between the two end cavities of the SSH chain.     

Adiabatic Decoupling and Time-Dependent Born–Oppenheimer Theory

We reconsider the time-dependent Born–Oppenheimer theory with the goal to carefully separate between the adiabatic decoupling of a given group of energy bands from their orthogonal subspace and the semiclassics within the energy bands. Band crossings are allowed and our results are local in the sense that they hold up to the first time when a band crossing is encountered. The adiabatic decoupling leads to an effective Schr?dinger equation for the nuclei, including contributions from the Berry connection. Received: 10 July 2000 / Accepted: 30 July 2001