Decay Of Metastable State Research Articles

Superquantum effects on physical systems from a hydrodynamic perspective

Employing a nonlinear time-dependent Schrödinger equation that describes the transition between quantum and classical regimes, we explore superquantum effects on physical systems from a hydrodynamic point of view. The degree of quantumness, a pivotal parameter in this transition equation, gauges the impact of quantum effects arising from the quantum potential. As this parameter varies continuously between zero and one, it facilitates the gradual transformation of systems from purely classical to entirely quantum regimes. We extend our analysis by setting the degree of quantumness greater than one, thereby investigating superquantum phenomena. Notably, this transition equation can be reframed as a scaled time-dependent Schrödinger equation with a rescaled Planck constant. Through computational simulations derived from the scaled Schrödinger equation, we examine superquantum implications for two systems, including Gaussian wave packet scattering from an Eckart barrier and metastable state decay. This research suggests that the hydrodynamic formulation of the quantum–classical transition equation offers a profound understanding of superquantum influences on physical systems.

Nonadiabatic decay of metastable states on coupled linear potentials

Avoided crossings of level pairs with opposite slopes can form potential-energy minima for the external degree of freedom of quantum particles, giving rise to metastable states on the avoided crossings (MSACs). Nonadiabatic decay of MSACs is studied by solving the two-component Schrödinger equation in diabatic and adiabatic representations. Non-perturbative lifetime values are found by evaluating wave function flux and scattering phases of time-independent solutions, as well as wave-function decay of time-dependent solutions. The values from these methods generally agree well, validating the utilized approaches. As the adiabaticity parameter, V, of the system is increased by about a factor of ten across the mixed diabatic/adiabatic regime, the MSAC character transitions from marginally to highly stable, with the lifetimes increasing by about ten orders of magnitude. The dependence of MSAC lifetime on the vibrational quantum number, ν, is discussed for several regimes of V. Time-dependent perturbation theory yields lifetimes that deviate by ≲30% from non-perturbative results, over the range of V and ν studied, while a semi-classical model based on Landau–Zener tunneling is up to a factor of twenty off. The results are relevant to numerous atomic and molecular systems with metastable states on intersecting, coupled potential energy curves.

Vacuum decay in quadratic gravity

Metastable states decay at zero temperature through quantum tunnelling at an exponentially small rate, which depends on the Coleman–de Luccia instanton, also known as bounce. In some theories, the bounce may not exist or its on-shell action may be ill-defined or infinite, thus hindering the vacuum decay process. In this paper, we test this possibility in modified theories of gravity interacting with a real scalar field. We consider an Einstein–Hilbert term with a non-minimally coupled scalar field and a quadratic Ricci scalar contribution. To tackle the problem, we use a new analytic method, with which we prove that the scalar field on the bounce has a universal behaviour at large Euclidean radii, almost independently of the potential. Our main result is that the quadratic Ricci scalar prevents the decay, regardless of the other terms in the action.

Activation-Tunneling Dynamics of Extended Systems in a Periodic Potential Relief

The dynamics of objects of various physical origins in barrier structures of superconductors, magnetic materials, quantum crystals and other solids is determined by the rate of fluctuation decay of metastable states in intermediate minima of a potential barrier. In a low-temperature region important for many nanotechnological applications, thermal fluctuations are frozen and are replaced by quantum fluctuations, which lead to a specific phase transition in the dynamics. The character of this transition in various systems is an analog of second-order or first-order transitions. The transition temperature is dependent on the degree of metastability and can be controlled by external load. This dependence is calculated for an extended nanosystem in an oblique periodic relief like a “washboard” in a wide range of varying the load, and the results generalize the results known before.

Fluctuational Dynamics of Extended Systems: Activation-Tunnel Frontier

The dynamics of systems in barrier structures is determined by the rate of the fluctuational decay of metastable states in a potential relief. The nature of the decay undergoes a qualitative change with a variation of the temperature. As the temperature decreases, thermal fluctuations freeze out and are replaced by quantum ones, which leads to a kind of phase transition in the dynamics. The transition temperature depends on the degree of metastability and can be controlled by an external load. This dependence is calculated for an extended nanosystem in an inclined periodic relief of the "washboard" type in a wide range of load changes. The obtained dependence generalizes the previously known results and can serve as the phase diagram of various dynamics mechanisms.

Активационно-туннельная динамика протяженных систем в периодическом потенциальном рельефе

The dynamics of systems in barrier structures is determined by the rate of fluctuation decay of metastable states in intermediate minima of the potential relief. When the temperature decreases, thermal fluctuations freeze out and are replaced by quantum ones, which leads to a kind of phase transition in the dynamics. The nature of this transition in various systems is analogous to either the second or first kind of transition. The transition temperature depends on the degree of metastability, and can be controlled by an external load. The purpose of this work is to calculate this dependence for an extended system in a tilted periodic relief of the "washboard" type in a wide range of load changes.

Study of foil explosion using the soft x-ray radiography

The experiments were carried out upon a research facility comprising three current generators. One of them was used to initiate the explosion of a foil and the other two, X-pinch backlighting sources were used for diagnostics. In the experiments, an upper limit has been determined for the decay time of the metastable state of a superheated metal. For aluminum, at a foil thickness of 6 μm and a deposited energy of 5.3 ± 0.5 kJ/g, the metastable state decay time was about 90 ns; for copper, at the same foil thickness and a deposited energy of 2.1 ± 0.3 kJ/g, it was about 250 ns; for nickel at the same foil thickness and a deposited energy of 1.3 ± 0.4 kJ/g, it was about 390 ns.

Foil explosion and decay of metastable state

The mechanism of decay of the superheated metastable metal produced by a thin foil explosion was investigated experimentally. The decay of the metastable metal was indicated by the occurrence of bubbles detected using soft x-ray backlighting. The experiments were carried out on a research facility comprising three current generators. One of them was used to initiate the explosion of a test foil, and the other two, X-pinch backlighting sources, were used for diagnostics. In the experiments, an upper limit has been determined for the decay time of the metastable state of a superheated metal. For aluminum, at a foil thickness of 6 μm and a deposited energy of 1.49 ± 0.08 eV/atom, the metastable state decay time was about 90 ns; for copper, at the same foil thickness and a deposited energy of 1.46 ± 0.07 eV/atom, it was about 250 ns. Analysis of the experimental results based on the classical nucleation theory has made it possible to estimate the work required for the formation of a critical bubble, the radius of the critical bubble, and the Tolman length, which characterizes the effect of the surface curvature on the surface tension. The work required for the formation of a critical bubble has been estimated to be 16.6 ± 1.5 eV for aluminum and 18.3 ± 1.2 eV for copper. The critical bubble radius and the Tolman length turned out to be several nanometers for both test metals.

Centered rarefaction wave with a liquid-gas phase transition in the approximation of “phase-flip” hydrodynamics

It is proposed to evaluate the effects of thermodynamic metastability on fluid dynamics by comparing two different ideal-hydrodynamics solutions --- one obtained with the fully equilibrium equation of state using the Maxwell construction, and the other in what we call the phase-flip approximation. The latter is based on the assumption of instantaneous decay of metastable states upon reaching the spinodal. The proposed method is applied to the classical problem of the centered rarefaction wave by expansion into vacuum, for which exact analytical solutions exist in both approximations. It is shown that the rapid decay of metastable states leads to the formation of a rarefaction shock in the expanding flow. Implications for the laser-heating experiments are discussed.

Metastable Fluid Decay During Electric Explosion of Metallic Foils

Results of experimental investigations into overheated metastable fluid decay during electric explosion of metallic foils are presented. Experiments have been performed using an experimental complex consisting of three current generators, one of which provides explosion of foil and two others – X-pinch-based radiographs – are used for diagnostic purposes. The upper limit of the decay time of an overheated metastable metal is determined experimentally. For aluminum conductor with deposited energy of (5.3 ± 0.5) kJ/g, the metastable state decay time is ~110 ns; for copper foil with deposited energy of (2.4 ± 0.2) kJ/g, it is ~260 ns; and for nickel foil with deposited energy of (1.3 ± 0.3) kJ/g, it is ~350 ns.

Two Oxygen-Coordinated Metastable Ru-ON States for Ruthenium Mononitrosyl Complex.

The properties of Ru-ON states were studied in cis-[RuNO(NH3)2(NO2)2OH] under illumination. The structure contains two nonequivalent complexes, and the metastable state was generated for both molecules with 19(1) and 31(1)% populations. The MS1 thermal decay occurs as a one-step process at about 240 K according to differential scanning calorimetry (DSC). For the first-order reaction, the frequency factor and activation energy for the decay process were determined as 2.0(2) × 10(13) s(-1) and 68.3(4) kJ mol(-1), respectively. Also, the simultaneous metastable state decay observed via DSC was in agreement with IR spectroscopy.

Overview: Understanding nucleation phenomena from simulations of lattice gas models.

Monte Carlo simulations of homogeneous and heterogeneous nucleation in Ising/lattice gas models are reviewed with an emphasis on the general insight gained on the mechanisms by which metastable states decay. Attention is paid to the proper distinction of particles that belong to a cluster (droplet), that may trigger a nucleation event, from particles in its environment, a problem crucial near the critical point. Well below the critical point, the lattice structure causes an anisotropy of the interface tension, and hence nonspherical droplet shapes result, making the treatment nontrivial even within the conventional classical theory of homogeneous nucleation. For temperatures below the roughening transition temperature facetted crystals rather than spherical droplets result. The possibility to find nucleation barriers from a thermodynamic analysis avoiding a cluster identification on the particle level is discussed, as well as the question of curvature corrections to the interfacial tension. For the interpretation of heterogeneous nucleation at planar walls, knowledge of contact angles and line tensions is desirable, and methods to extract these quantities from simulations will be mentioned. Finally, also the problem of nucleation near the stability limit of metastable states and the significance of the spinodal curve will be discussed, in the light of simulations of Ising models with medium range interactions.

Time arrow is influenced by the dark energy.

The arrow of time and the accelerated expansion are two fundamental empirical facts of the universe. We advance the viewpoint that the dark energy (positive cosmological constant) accelerating the expansion of the universe also supports the time asymmetry. It is related to the decay of metastable states under generic perturbations, as we show on example of a microcanonical ensemble. These states will not be metastable without dark energy. The latter also ensures a hyperbolic motion leading to dynamic entropy production with the rate determined by the cosmological constant.

Decay of Metastable State with Account of Agglomeration and Relaxation Processes

Theoretical description of the metastable phase decay kinetics in the presence of specific connections between the embryos of small sizes has been given. The theory of the decay kinetics in the presence of relaxation processes is constructed in analytical manner. The m-mers nucleation is investigated and the global kinetics of decay is also constructed in this case analytically.

The interference of fluctuations in the kinetics of metastable state decay

The interference of nucleation-rate fluctuations during metastable state decay has been considered. The effects have been shown to be always weak; therefore, averaged parameters may be used to construct the kinetics of the process.

Lifetime of low vibrational levels of the metastableB̃2B2state ofH2O+probed by photodissociation at 532 nm

The decay of metastable states of the water radical cation ${\text{H}}_{2}{\text{O}}^{+}$ has been observed in an experiment that combines photofragment momentum imaging and electrostatic ion-beam trapping in a crossed-beam geometry. Photoabsorption of 532-nm laser light from a fast beam of ${\text{H}}_{2}{\text{O}}^{+}$ is observed to yield fragmentation into both OH${}^{0}+{\mathrm{H}}^{+}$ and OH${}^{+}+{\mathrm{H}}^{0}$. Using coincident photofragment momentum imaging, the initial state of the observed photofragmentation is associated with low vibrational levels of the second excited $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{B}\phantom{\rule{0.16em}{0ex}}{}^{2}{B}_{2}$ state of ${\text{H}}_{2}{\text{O}}^{+}$, dissociating via absorption onto a repulsive part of the $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{A}\phantom{\rule{0.16em}{0ex}}{}^{2}{A}_{1}$ state. Electrostatic ion trapping in the laser interaction region is used to follow the photofragment intensity as a function of time and to determine the lifetime of the metastable states to be ${\ensuremath{\tau}}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{B}\phantom{\rule{0.16em}{0ex}}{}^{2}{B}_{2}}=198\ifmmode\pm\else\textpm\fi{}11$ $\ensuremath{\mu}$s.

Quick and easy escape from a metastable state

An elementary but complete calculation of metastable state decay from a piecewise-constant one-dimensional potential well is presented that does not invoke the concept of an attempt frequency or require a knowledge of the Wentzel-Kramers-Brillouin method. Connection is made with scattering resonances for advanced readers.

Dissipative Enhancement of the Supercurrent inTl2Ba2CaCu2O8Intrinsic Josephson Junctions

We have measured dissipation-induced localization of the reaction coordinate for a metastable-state decay process in a model system with moderate damping. Specifically, the supercurrent in an array of Tl2Ba2CaCu2O8 intrinsic Josephson junctions is larger when all the junctions are in the zero-voltage state than when one or more junctions are in the voltage state since the dissipation is larger in the former case.

Judd–Ofelt treatment on luminescence of europium complexes with β-diketone and bis(β-diketone)

Eu(DBM) 32H 2O and Eu 2(DDBM) 3H 2O were synthesized by reactions between EuCl 3 and chelating regents of β-diketone (dibenzoylmethane, HDBM) and bis(β-diketone) (1,3-bis(3-phenyl-3-oxopropanoyl)benzene, H 2DDBM), respectively, and their luminescence properties were investigated by the fluorescence spectra and metastable state decay spectra. It was found that the relative intensity ratio of 5D 0→ 7F 2 to 5D 0→ 7F 1transition and the radiative lifetime shows a little change attributing to the different symmetry of europium ions, which Ω 2 of Eu complexes with β-diketone and bis(β-diketone) are 13.08 and 12.24, respectively. Moreover, it was also found that the metastable state lifetime of Eu 2(DDBM) 3H 2O is much longer than that of Eu(DBM) 32H 2O, due to smaller water quenching and lower triplet level of ligands. The Commission Internacionale d’Éclairage (CIE) chromaticity coordinates calculated from emission spectrum are x=0.637 and y=0.343 for Eu 2(DDBM) 3H 2O, which presents high red color purity near 100%.

Rate processes and decay of metastable states inside an anharmonic well driven by a random zero-point field

A procedure previously developed by us for the evaluation of the diffusion coefficient and drift velocity of a charged Newtonian particle in a zero-point field is applied here to a sextic potential-one-dimensional system, for which an exact solution to the related Hamilton-Jacobi-Yasue-Riccati equation is available. This potential energy function represents either a stiff single well or a triple well. For this model, the averaged diffusion coefficient has been evaluated by assuming that the particle under study is confined for a long time inside one anharmonic well, that is, in the limit of infinite relaxation time, and the results are compared with quantum-mechanical predictions. A double-well model potential is subsequently examined.