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Open systems, or systems that interact with their surroundings, can contain selfconsistent but unstable solutions that are referred to as resonances. Resonances are often sensitive to a narrow band of frequencies and can have long lifetimes, but they also couple to the environment and their calculation can be challenging compared to the simulation of the bound states of a closed system. In this dissertation, a new transparent boundary method is proposed to target the resonances of open systems. This method allows for the highly accurate calculation of resonances using smaller computational domains than are achievable with traditional boundary methods. To implement the proposed boundary approach for a given system, the domain is separated into two regions: one for the interior of the system and one for the environment. Expressions are first found for the resonances in the exterior region, which are then used to establish boundary conditions for a numerical treatment of the interior region. The use of the exterior expressions as a part of the interior treatment results in a nonlinear eigenvalue problem, which we resolve using a simple iteration procedure. The proposed method is first applied to the Stark system in quantum mechanics for the calculation of Stark resonances. These resonances are non-Hermitian quantum states that arise when a central potential is subjected to a linear field term, allowing the electron to escape and tunnel to infinity, and they can be used to calculate the nonlinear optical properties of atomic and molecular species. Two implementations are given for the treatment of the Stark system, using different assumptions and formulations to achieve highly accurate solutions for the Stark resonances of atomic hydrogen. The simple iteration procedure is shown to be sufficient to resolve the nonlinear nature of the eigenvalue problem for these scalar systems. The proposed method is also used to perform first-of-their-kind three-dimensional calculation

The climate is a complex, chaotic system with many degrees of freedom. Attaining a deeper level of understanding of climate dynamics is an urgent scientific challenge, given the evolving climate crisis. In statistical physics, many-particle systems are studied using Large Deviation Theory (LDT). A great potential exists for applying LDT to problems in geophysical fluid dynamics and climate science. In particular, LDT allows for understanding the properties of persistent deviations of climatic fields from long-term averages and for associating them to low-frequency, large-scale patterns. Additionally, LDT can be used in conjunction with rare event algorithms to explore rarely visited regions of the phase space. These applications are of key importance to improve our understanding of high-impact weather and climate events. Furthermore, LDT provides tools for evaluating the probability of noise-induced transitions between metastable climate states. This is, in turn, essential for understanding the global stability properties of the system. The goal of this review is manifold. First, we provide an introduction to LDT. We then present the existing literature. Finally, we propose possible lines of future investigations. We hope that this paper will prepare the ground for studies applying LDT to solve problems encountered in climate science and geophysical fluid dynamics.

The climate is a complex, chaotic system with many degrees of freedom. Attaining a deeper level of understanding of climate dynamics is an urgent scientific challenge, given the evolving climate crisis. In statistical physics, many-particle systems are studied using Large Deviation Theory (LDT). A great potential exists for applying LDT to problems in geophysical fluid dynamics and climate science. In particular, LDT allows for understanding the properties of persistent deviations of climatic fields from long-term averages and for associating them to low-frequency, large-scale patterns. Additionally, LDT can be used in conjunction with rare event algorithms to explore rarely visited regions of the phase space. These applications are of key importance to improve our understanding of high-impact weather and climate events. Furthermore, LDT provides tools for evaluating the probability of noise-induced transitions between metastable climate states. This is, in turn, essential for understanding the global stability properties of the system. The goal of this review is manifold. First, we provide an introduction to LDT. We then present the existing literature. Finally, we propose possible lines of future investigations. We hope that this paper will prepare the ground for studies applying LDT to solve problems encountered in climate science and geophysical fluid dynamics.

The climate is a complex, chaotic system with many degrees of freedom. Attaining a deeper level of understanding of climate dynamics is an urgent scientific challenge, given the evolving climate crisis. In statistical physics, many-particle systems are studied using Large Deviation Theory (LDT). A great potential exists for applying LDT to problems in geophysical fluid dynamics and climate science. In particular, LDT allows for understanding the properties of persistent deviations of climatic fields from long-term averages and for associating them to low-frequency, large-scale patterns. Additionally, LDT can be used in conjunction with rare event algorithms to explore rarely visited regions of the phase space. These applications are of key importance to improve our understanding of high-impact weather and climate events. Furthermore, LDT provides tools for evaluating the probability of noise-induced transitions between metastable climate states. This is, in turn, essential for understanding the global stability properties of the system. The goal of this review is manifold. First, we provide an introduction to LDT. We then present the existing literature. Finally, we propose possible lines of future investigations. We hope that this paper will prepare the ground for studies applying LDT to solve problems encountered in climate science and geophysical fluid dynamics.

The climate is a complex, chaotic system with many degrees of freedom. Attaining a deeper level of understanding of climate dynamics is an urgent scientific challenge, given the evolving climate crisis. In statistical physics, many-particle systems are studied using Large Deviation Theory (LDT). A great potential exists for applying LDT to problems in geophysical fluid dynamics and climate science. In particular, LDT allows for understanding the properties of persistent deviations of climatic fields from long-term averages and for associating them to low-frequency, large-scale patterns. Additionally, LDT can be used in conjunction with rare event algorithms to explore rarely visited regions of the phase space. These applications are of key importance to improve our understanding of high-impact weather and climate events. Furthermore, LDT provides tools for evaluating the probability of noise-induced transitions between metastable climate states. This is, in turn, essential for understanding the global stability properties of the system. The goal of this review is manifold. First, we provide an introduction to LDT. We then present the existing literature. Finally, we propose possible lines of future investigations. We hope that this paper will prepare the ground for studies applying LDT to solve problems encountered in climate science and geophysical fluid dynamics.

The climate is a complex, chaotic system with many degrees of freedom. Attaining a deeper level of understanding of climate dynamics is an urgent scientific challenge, given the evolving climate crisis. In statistical physics, many-particle systems are studied using Large Deviation Theory (LDT). A great potential exists for applying LDT to problems in geophysical fluid dynamics and climate science. In particular, LDT allows for understanding the properties of persistent deviations of climatic fields from long-term averages and for associating them to low-frequency, large-scale patterns. Additionally, LDT can be used in conjunction with rare event algorithms to explore rarely visited regions of the phase space. These applications are of key importance to improve our understanding of high-impact weather and climate events. Furthermore, LDT provides tools for evaluating the probability of noise-induced transitions between metastable climate states. This is, in turn, essential for understanding the global stability properties of the system. The goal of this review is manifold. First, we provide an introduction to LDT. We then present the existing literature. Finally, we propose possible lines of future investigations. We hope that this paper will prepare the ground for studies applying LDT to solve problems encountered in climate science and geophysical fluid dynamics.

This issue is concerned with structural and phase transitions in heterogeneous and composite materials, the effects of external magnetic fields on these phenomena and the macroscopic properties and behaviour of materials with isotropic and anisotropic internal structures. Using experimental, theoretical and computer methods, these transitions are studied at the atomic and mesoscopic levels. The fundamental specific feature of structural transitions in many heterogeneous media consists of the fact that these transitions are stacked for a long time in non-equilibrium states that appear due to either macroscopic dissipative processes (an alternating magnetic field or hydrodynamic flow, for instance) or system lifetime in a metastable state. It is important to explain and describe these transitional states using the general approach of non-equilibrium physical mechanics. The review and research articles in the issue will cover the whole spectrum of scales (from nano to macro) and materials (from metastable liquids to biological polymers) in order to exhibit recently developed trends in the field of heterogeneous materials. Atomistic modelling, structuring induced by external magnetic fields and hydrodynamic flows, metastable and non-ergodic states, mechanical properties and phenomena in heterogeneous materials-all these are covered. This article is part of the theme issue 'Heterogeneous materials: Metastable and non-ergodic internal structures'. ©2019 The Author(s)Published by the Royal Society.

The bound states of two interacting two-dimensional magnetoexcitons with electrons and holes on the lowest Landau levels (LLLs) moving in-plane of the layer with equal but opposite oriented wave vectors and forming a molecular-type structures with the resultant wave vector (k) over right arrow = 0 were investigated. Four possible spin structures of two electrons and of two holes forming the bound states were considered. Two of them lead to the formation of the para and ortho magnetoexcitons in the presence of the electron-hole (e-h) Coulomb exchange interaction. In this case we have studied the interaction of two para magnetoexcitons and of two ortho magnetoexcitons with the resultant spin equal to zero. Another two variant, are actual when the Coulomb exchange e-h interaction is negligible small and the spin of two electrons separately and the effective spin of two holes are interconected and forms the singlet or the triplet states with zero spin projections on the magnetic field direction. The spin states of the four particles were constructed combining the singlet two electron state with the singlet two hole state as well as the triplet two electron state with the triplet two hole state. Only the bound states of two electrons and of two holes with singlet-singlet and with triplet-triplet spin structures were studied. It was shown that the spin structure of the type singlet-triplet and triplet-singlet do not exist due to the hidden symmetry of the magnetoexcitons. The orbital structure of the 2D magnetoexciton with wave vector (k) over right arrow not equal 0 is similar with an in-plane electric dipole with the dipole moment perpendicularly oriented to the wave vector. The bimagnetoexciton with resultant wave vector (k) over right arrow = 0 is composed from two antiparallel oriented electric dipoles moving with antiparallel wave vectors (k) over right arrow not equal 0 Their relative motion in the frame of the bound states is characterized by the variational wave, QC 20190313

The molecules and atoms that comprise matter have the tendency to join in different aggregation states called phases. How these atoms and molecules manage to shift between these different states is one of the most fascinating processes in physics. These phase transitions are commonly controlled and triggered by a non-equilibrium physical mechanism, called nucleation, that describes the formation of the first seeds of the new phase. Nucleation is behind many phenomena of utmost scientific and technological interest, ranging from nuclear phenomena and biological assembly to galaxy formation. However, due to its rare non-equilibrium nature, it is still one of the few classical problems that remain incompletely understood. Indeed, deviations between theoretical predictions and experiments can reach several orders of magnitude. In this article, we review the essential aspects of nucleation and the challenges it poses to current research. [Contrib Sci 11(2): 173-180 (2015)]Keywords: phase transition · non-equilibrium · nucleation · metastable states · water

We have transformed the Scott's model of protein Hamiltonian to metastable form, by means of double coherent unitary transformation. It turned out that in metastable Hamiltonian the number of quasi particles is not conserved due to the forming of pairs of excitations. The energies of pairs are found and their population is quoted. It is interesting that elementary excitations of metastable state behave similarly as excitations of molecular vibration field as well as excitations of electromagnetic field.

We have transformed the Scott's model of protein Hamiltonian to metastable form, by means of double coherent unitary transformation. It turned out that in metastable Hamiltonian the number of quasi particles is not conserved due to the forming of pairs of excitations. The energies of pairs are found and their population is quoted. It is interesting that elementary excitations of metastable state behave similarly as excitations of molecular vibration field as well as excitations of electromagnetic field.

The Lifshitz - Slezov theory is applied to study the metastable statesof the matrix damage clusters, MDs, and the copper enriched clusters, CECs, in neutron irradiated steels. It was found that under irradiation conditions the CECs are at the Ostwald stage for a neutron fluence of about 0.0002 dpa. The time dependence of number density, MDN, is determined by summarizing all differential equations of the master equation for MDs with neglecting of dimmers concentration in comparison with concentration of the single vacancies and subtraction of the number CECs that replace the MDs, namely vacancy clusters, due to the diffusivity of copper and other impurity atoms to them. For binary Fe-0.3wt%Cu under neutron irradiation with dose 0.026, 0.051, 0.10 and 0.19 dpa the volume content of the precipitates from the SANS experiment is found to be about 0.229, 0.280, 0.237 and 0.300 vol% respectively. The volume fraction of CECs in these samples is 0.195 vol% and the calculated volume fraction of MDs is 0.034, 0.085, 0.042 and 0.105 vol% for doses 0.026, 0.051, 0.10 and 0.19 dpa respectively.

An atom or ion can change quantum state, usually through emission or absorption of a photon. The photon has the same energy as the energy difference between the states of the transition. The states, or energy levels, of an atom are quantized and light emitted, or absorbed, from the atom is therefore of specific wavelengths, giving spectral lines. The spectrum of an atomic ion is unique and contains information of the structure and energy levels of the ion. The spectrum of an atom can be used as a fingerprint in determinations of the abundance of the element in different objects. This thesis is focused on some weak effects observed by spectroscopy. Although the effects are weak, they turn out to be of great importance. According to quantum mechanics transitions between certain states are not allowed. Here the weak effects open the possibility for transitions. Spectral lines from forbidden transitions are very weak and difficult to observe under ordinary laboratorial conditions, but they are commonly observed from astrophysical objects and can be very useful for diagnostics of astrophysical plasmas. The first reported observation of forbidden lines was from an astrophysical object and at that time supposed to be from new, previous unknown, elements. If all possible decay channels from an energy level are forbidden, the energy level is metastable and has usually a lifetime 10$^8$ times longer than an ordinary excited state. Measurements of such long lifetimes are difficult since the ion need to be confined during the observation time. Confinement of ions can be achieved with a storage device, such as a storage ring or a trap, where the ions are stored without interacting with each other or the surroundings. A laser probing technique has been developed at the storage ring CRYRING, for measurements of lifetimes of metastable states. The technique has now been improved for measurement of longer lifetimes. The technique has also been modified to fit when measuring on negat

An atom or ion can change quantum state, usually through emission or absorption of a photon. The photon has the same energy as the energy difference between the states of the transition. The states, or energy levels, of an atom are quantized and light emitted, or absorbed, from the atom is therefore of specific wavelengths, giving spectral lines. The spectrum of an atomic ion is unique and contains information of the structure and energy levels of the ion. The spectrum of an atom can be used as a fingerprint in determinations of the abundance of the element in different objects. This thesis is focused on some weak effects observed by spectroscopy. Although the effects are weak, they turn out to be of great importance. According to quantum mechanics transitions between certain states are not allowed. Here the weak effects open the possibility for transitions. Spectral lines from forbidden transitions are very weak and difficult to observe under ordinary laboratorial conditions, but they are commonly observed from astrophysical objects and can be very useful for diagnostics of astrophysical plasmas. The first reported observation of forbidden lines was from an astrophysical object and at that time supposed to be from new, previous unknown, elements. If all possible decay channels from an energy level are forbidden, the energy level is metastable and has usually a lifetime 10$^8$ times longer than an ordinary excited state. Measurements of such long lifetimes are difficult since the ion need to be confined during the observation time. Confinement of ions can be achieved with a storage device, such as a storage ring or a trap, where the ions are stored without interacting with each other or the surroundings. A laser probing technique has been developed at the storage ring CRYRING, for measurements of lifetimes of metastable states. The technique has now been improved for measurement of longer lifetimes. The technique has also been modified to fit when measuring on negat

An atom or ion can change quantum state, usually through emission or absorption of a photon. The photon has the same energy as the energy difference between the states of the transition. The states, or energy levels, of an atom are quantized and light emitted, or absorbed, from the atom is therefore of specific wavelengths, giving spectral lines. The spectrum of an atomic ion is unique and contains information of the structure and energy levels of the ion. The spectrum of an atom can be used as a fingerprint in determinations of the abundance of the element in different objects. This thesis is focused on some weak effects observed by spectroscopy. Although the effects are weak, they turn out to be of great importance. According to quantum mechanics transitions between certain states are not allowed. Here the weak effects open the possibility for transitions. Spectral lines from forbidden transitions are very weak and difficult to observe under ordinary laboratorial conditions, but they are commonly observed from astrophysical objects and can be very useful for diagnostics of astrophysical plasmas. The first reported observation of forbidden lines was from an astrophysical object and at that time supposed to be from new, previous unknown, elements. If all possible decay channels from an energy level are forbidden, the energy level is metastable and has usually a lifetime 10$^8$ times longer than an ordinary excited state. Measurements of such long lifetimes are difficult since the ion need to be confined during the observation time. Confinement of ions can be achieved with a storage device, such as a storage ring or a trap, where the ions are stored without interacting with each other or the surroundings. A laser probing technique has been developed at the storage ring CRYRING, for measurements of lifetimes of metastable states. The technique has now been improved for measurement of longer lifetimes. The technique has also been modified to fit when measuring on negat

An atom or ion can change quantum state, usually through emission or absorption of a photon. The photon has the same energy as the energy difference between the states of the transition. The states, or energy levels, of an atom are quantized and light emitted, or absorbed, from the atom is therefore of specific wavelengths, giving spectral lines. The spectrum of an atomic ion is unique and contains information of the structure and energy levels of the ion. The spectrum of an atom can be used as a fingerprint in determinations of the abundance of the element in different objects. This thesis is focused on some weak effects observed by spectroscopy. Although the effects are weak, they turn out to be of great importance. According to quantum mechanics transitions between certain states are not allowed. Here the weak effects open the possibility for transitions. Spectral lines from forbidden transitions are very weak and difficult to observe under ordinary laboratorial conditions, but they are commonly observed from astrophysical objects and can be very useful for diagnostics of astrophysical plasmas. The first reported observation of forbidden lines was from an astrophysical object and at that time supposed to be from new, previous unknown, elements. If all possible decay channels from an energy level are forbidden, the energy level is metastable and has usually a lifetime 10$^8$ times longer than an ordinary excited state. Measurements of such long lifetimes are difficult since the ion need to be confined during the observation time. Confinement of ions can be achieved with a storage device, such as a storage ring or a trap, where the ions are stored without interacting with each other or the surroundings. A laser probing technique has been developed at the storage ring CRYRING, for measurements of lifetimes of metastable states. The technique has now been improved for measurement of longer lifetimes. The technique has also been modified to fit when measuring on negat

An atom or ion can change quantum state, usually through emission or absorption of a photon. The photon has the same energy as the energy difference between the states of the transition. The states, or energy levels, of an atom are quantized and light emitted, or absorbed, from the atom is therefore of specific wavelengths, giving spectral lines. The spectrum of an atomic ion is unique and contains information of the structure and energy levels of the ion. The spectrum of an atom can be used as a fingerprint in determinations of the abundance of the element in different objects. This thesis is focused on some weak effects observed by spectroscopy. Although the effects are weak, they turn out to be of great importance. According to quantum mechanics transitions between certain states are not allowed. Here the weak effects open the possibility for transitions. Spectral lines from forbidden transitions are very weak and difficult to observe under ordinary laboratorial conditions, but they are commonly observed from astrophysical objects and can be very useful for diagnostics of astrophysical plasmas. The first reported observation of forbidden lines was from an astrophysical object and at that time supposed to be from new, previous unknown, elements. If all possible decay channels from an energy level are forbidden, the energy level is metastable and has usually a lifetime 10$^8$ times longer than an ordinary excited state. Measurements of such long lifetimes are difficult since the ion need to be confined during the observation time. Confinement of ions can be achieved with a storage device, such as a storage ring or a trap, where the ions are stored without interacting with each other or the surroundings. A laser probing technique has been developed at the storage ring CRYRING, for measurements of lifetimes of metastable states. The technique has now been improved for measurement of longer lifetimes. The technique has also been modified to fit when measuring on negat

An atom or ion can change quantum state, usually through emission or absorption of a photon. The photon has the same energy as the energy difference between the states of the transition. The states, or energy levels, of an atom are quantized and light emitted, or absorbed, from the atom is therefore of specific wavelengths, giving spectral lines. The spectrum of an atomic ion is unique and contains information of the structure and energy levels of the ion. The spectrum of an atom can be used as a fingerprint in determinations of the abundance of the element in different objects. This thesis is focused on some weak effects observed by spectroscopy. Although the effects are weak, they turn out to be of great importance. According to quantum mechanics transitions between certain states are not allowed. Here the weak effects open the possibility for transitions. Spectral lines from forbidden transitions are very weak and difficult to observe under ordinary laboratorial conditions, but they are commonly observed from astrophysical objects and can be very useful for diagnostics of astrophysical plasmas. The first reported observation of forbidden lines was from an astrophysical object and at that time supposed to be from new, previous unknown, elements. If all possible decay channels from an energy level are forbidden, the energy level is metastable and has usually a lifetime 10$^8$ times longer than an ordinary excited state. Measurements of such long lifetimes are difficult since the ion need to be confined during the observation time. Confinement of ions can be achieved with a storage device, such as a storage ring or a trap, where the ions are stored without interacting with each other or the surroundings. A laser probing technique has been developed at the storage ring CRYRING, for measurements of lifetimes of metastable states. The technique has now been improved for measurement of longer lifetimes. The technique has also been modified to fit when measuring on negat

We analyze the ordering dynamics of the voter model in different classes of complex networks. We observe that whether the voter dynamics orders the system depends on the effective dimensionality of the interaction networks. We also find that when there is no ordering in the system, the average survival time of metastable states in finite networks decreases with network disorder and degree heterogeneity. The existence of hubs in the network modifies the linear system size scaling law of the survival time. The size of an ordered domain is sensitive to the network disorder and the average connectivity, decreasing with both; however it seems not to depend on network size and degree heterogeneity.

The enhancement of resonant sum-frequency generation through quantum control, which employs the continuum states, was discussed. The scheme employs all-resonant coupling and trade-off optimization of the constructive and destructive quantum interference effects in the higher-order and lower-order polarizations controlled by the overlap of two autoionizinglike laser-induced continuum structure. It was found that the analytical solution of coupled density-matrix equations were implemented for analysis of the solution of Maxwell's equation describing four-wave mixing. The results show that the feasibility of the nearly complete conversion of low-frequency radiation to sum frequency radiation was shown for the case of quasiresonant coupling., QC 20141210

We propose a relation for the work of critical cluster formation in nucleation theory W for the systems with long-range interparticle interactions. The method of bridge functions is used to combine the system behavior at sufficiently small quenches, adequately predicted by the classical nucleation theory, with nonclassical effects at deep quenches in the vicinity of the thermodynamic spinodal, described within the framework of the field theoretical approach with an appropriate Ginzburg-Landau functional. The crossover between the two types of nucleation behavior takes place in the vicinity of the kinetic spinodal where the lifetime of a metastable state is of the order of the relaxation time to local equilibrium. We argue that the kinetic spinodal corresponds to the minimum of the excess number of molecules in the critical cluster. This conjecture leads to the form of W containing no adjustable parameters. The barrier scaling function ? = W/Wcl, where Wcl is the classical nucleation barrier, depends parametrically on temperature through the dimensionless combination of material properties. The results for argon nucleation are presented., Geotechnology, Civil Engineering and Geosciences

We propose a relation for the work of critical cluster formation in nucleation theory W for the systems with long-range interparticle interactions. The method of bridge functions is used to combine the system behavior at sufficiently small quenches, adequately predicted by the classical nucleation theory, with nonclassical effects at deep quenches in the vicinity of the thermodynamic spinodal, described within the framework of the field theoretical approach with an appropriate Ginzburg-Landau functional. The crossover between the two types of nucleation behavior takes place in the vicinity of the kinetic spinodal where the lifetime of a metastable state is of the order of the relaxation time to local equilibrium. We argue that the kinetic spinodal corresponds to the minimum of the excess number of molecules in the critical cluster. This conjecture leads to the form of W containing no adjustable parameters. The barrier scaling function ? = W/Wcl, where Wcl is the classical nucleation barrier, depends parametrically on temperature through the dimensionless combination of material properties. The results for argon nucleation are presented., Geotechnology, Civil Engineering and Geosciences

We investigate the collisional quenching of cold metastable antiprotonic atomcules [(p) over bar He+], by HZ molecules in view of the recent state-resolved measurements at CERN. Firstly, we determine ab initio the 6-D intermolecular interaction between the four (anti)nuclei at the CCSD(T)/CP level. After averaging the interaction over the fast (p) over bar orbits, we exhibit reactive channels and activation barriers below few 100 muE(h). Hence, we account qualitatively for the order of magnitude and (n,l) dependence of the quenching cross-sections measured at 30 K, after estimating tunneling probabilities. We also account for the lower quenching efficiency by deuterium. However improving this overall agreement would require the determination of numerous finer contributions. We monitor the saturation of electronic correlation with larger basis sets; we estimate the importance of dynamical relaxation effects; and we stress the role of quantum vibrational and rotational delocalization for the light (p, (p) over bar) nuclei. The latter vibrational corrections lower the barriers, while the rotational H-2 averaging defavours isotropic para-H-2 (J = 0). As a result, we mainly attribute the quenching at 30 K to ortho-H-2 (J = 1). Additional experiments at other temperatures and with para-H-2 would further constrain this orthopara quenching selectivity, and provide an ideal four-body benchmark for further chemical physics investigations (including tunneling effects, collision-induced Auger decay, etc)., QC 20100525

We investigate the reactive association of metastable antiprotonic helium 'atomcules' ([(p) over bar He+](nt)) with positronium(Ps). In the framework of the Born-Oppenheimer approximation, we further discuss the evolution and stability of the intermediate complex (alpha, (p) over bar, e(+), 2e(-)) using a classical trajectory approach for treating the nuclei (alpha, (p) over bar) We predict two possible channels for the atomcule-Ps reaction depending upon the atomcule principal quantum number n : II greater than or equal to 38 states dissociate to (H) over bar, whereas, it < 38 states form a new class of metastable atomcules, which could be confirmed by laser spectroscopy. The present work illustrates the pertinence of simple chemical physics concepts to the study of exotic processes involving antimatter., QC 20100525

We investigate the collisional survival of antiprotonic (p) over bar He+ atomcules in pure helium from a detailed ab initio analysis of their intermolecular interaction. After averaging over classical (p) over bar orbits, we attribute the collisional stability of thermalized atomcules to the existence of a high activation barrier due to Pauli repulsion. Our model predicts the reduction of the barrier for outer (p) over bar orbits, thus accounting for the quenching of high n states by He atoms. We also investigate the thermalization stage of newly formed atomcules from a classical trajectory Monte Carlo approach. Our results support the destruction of the states with n greater than or equal to 41, as well as the strong depopulation of all n < 41 layers, with a quenching rate of 50% at least. Assuming a statistical distribution of newly formed atomcules with respect to their initial angular momentum, we account for the 3% observed trapping fraction of metastable states. <(c)> 2001 Elsevier Science B.V. All rights reserved., QC 20100525

The effects of mobile vacancies on the dynamics of ordering processes and phase separation in multicomponent systems are studied via Monte Carlo simulations of a two-dimensional seven-state ferromagnetic Potts model with varying degrees of site dilution. The model displays phase equilibria corresponding to a dilute Potts-disordered (fluid) phase and a dilute Potts-ordered phase (solid), as well as a broad region of coexistence between the fluid and the solid phase. Temperature quenches into the dilute Potts-ordered phase as well as into the phase-separated region are considered under the condition of conserved vacancy density and nonconserved Potts order. The dynamics of ordering and phase separation is found to follow algebraic growth laws with exponent values that depend on the phase to which the quench is performed. Strong transient effects are observed in the dilute Potts-ordered phase, which are shown to result from an accumulation of vacancies at the domain boundaries. These transient effects are accompanied by an overshooting effect in the local order of the growing domains.

Highly excited vibrational levels of ground state iodine, and all levels of the metastable state, are involved in processes leading to the dissociation of I2 in the chemical oxygen iodine laser (COIL). Populations in these vibrationally and vibronically excited levels can be sensitively monitored by exciting laser induced fluorescence (LIF) from the valance to ion-pair transitions. However, accurate spectroscopic constants are required for the extraction of population distributions from spectral intensity data. Constants for the systems were obtained from rotationally resolved spectra for jet cooled, metastable I2. Studies of matrix isolated I2 and IBr were undertaken in order to examine their electronic relaxation dynamics in simple cryogenic solids, and to determine the A and A' state radiative decay rates. Large matrix shifts were observed, caused by solvation of the excited state dipole. It is probable that an optically pumped laser, operating on the D'-A' transition of Ar matrix isolated I2, could be constructed.

This project involves three separate tasks with the following titles: Task I - Generation of low frequency sound from optical pulses; Task II - Propagation of sound through a gas with an overpopulation of vibrationally excited states; and Task III - Optoacoustic studies in liquids. The three tasks, funded by the physics division of ONR, represent a three-pronged study of the generation of sound by the absorption of light and amplification of a propagating sound wave. Generation of low frequency sound from a series of optical pulses involves optimizing the density of pulses to obtain maximum energy at low frequencies. The present effort is devoted to numerical simulation. With present modulation schemes, as much as 50% of the energy appears in the desired fundamental, but predicted harmonic distortion is unacceptable. Amplification of sound propagating through gas with an overpopulation of vibrationally excited states has now been observed in N2/H2,N2/He, and N2/CH4 mixtures. The gas is excited with an electrical discharge. Present efforts are devoted to achieving better agreement between theory and experiment. Optoacoustic pulse have been observed in several alcohols and water. The optoacoustic amplitude has been observed as a function of laser energy, distance from excitation zone to detection region, and optical absorption coefficient. (Author)

Preliminary investigation of applying nonlinear optical effects in conjunction with the optogalvanic effect to achieve laser controlled opening switch was proposed in the low cost grant. It should be mentioned at the onset that this work was limited by the budget and that its purpose was mainly to define the problems and establish feasibilities. A crucial step is a match of mutual virtual level. Within the budget limitation, a few important steps were made: a) Detailed study of the plasma processes taking a major role in the opto-galvanic effect such as Penning ionization and direct electron impact inoization and their relative importance; b) the use of dye lasers according to the Raman scheme; c) Penning ionization in Hg/Ne and Sr/Ne(3) has been studied within the grant. A recent investigation the role of direct electron multistep ionization. The consequences are that although Penning ionization is an important process in the discharge it does not control it sustaining the discharge. In investigating the nonlinear effect little progress was made other than formalizing and defining the problems. (Author)

The objective of this program has been the determination of spectroscopic and radiative lifetime data for the low energy, metastable states of the halogens and interhalogens. This information was obtained by recording wavelength and time resolved laser excitation spectra for molecules isolated in rare gas matrices.

Wannier-Stark states for semiconductor superlattices in strong static fields, where the interband Landau-Zener tunneling cannot be neglected, are rigorously calculated. The lifetime of these metastable states was found to show multiscale oscillations as a function of the static field, which is explained by an interaction with above-barrier resonances. An equation, expressing the absorption spectrum of semiconductor superlattices in terms of the resonance Wannier-Stark states is obtained and used to calculate the absorption spectrum in the region of high static fields.