Table of contents

Bandgap renormalization for the geometry of T-shaped quantum wires is calculated as a function of the electron–hole plasma density and quantum wire width in the random phase approximation. Considering a suitable confinement potential, a numerical scheme has been proposed to calculate the screened Coulomb potential, profile of charge density with various quantum wire widths and relative renormalization of gap energy. We will show that carrier concentration, screened confinement potential and relative bandgap renormalization are functions of the ratio of well width in the x and y directions. We also show that increasing temperature leads to more relative renormalization of gap energy.

Lattice dynamical investigation on the Ni_0.3Fe_0.7-H system has been carried out to calculate the phonon dispersion for Fe rich Ni-Fe alloy along the [100], [101] and [111] directions. A reasonably good agreement is found between the computed and experimental results. Phonon density of states, specific heat and the Debye temperature are also calculated and the results are compared with the available results of others. The mean square displacement of atoms surrounding the interstitial hydrogen atom and the defect modes are also reported.

We analyse non-local correlations in Bohm trajectories of two particles that are entangled in a configuration space. We use a one-dimensional model that explicitly describes the space-time evolution of a two-particle entangled state. This analysis substantiates the geometrical, schematic approach that was used by Rice to demonstrate the non-locality in the Bohm theory of quantum mechanics. We further discuss a subtle aspect of the non-local correlations that was not revealed in Rice's analysis.

Considering a piezo-plasma-like medium with hexagonal symmetry whose main symmetry axis is parallel to the z-axis and approximating it by an isotropic medium, the coupling of the elastic waves with plasma properties of the medium is studied. In this case, the coupled surface quasi-elasto-electromagnetic wave propagating on the interface of a piezoelectric with vacuum, making use of the mirror reflection model, is investigated. It is shown that the piezo-effect can result in the plasma damping of the elastic oscillations.

We present momentum-space properties of multiply ionized atoms as a function of atomic number Z and the degree of ionization of the atom. In particular, we have calculated the Compton profiles of all possible electronic configurations of He, Li, Be, B and N atoms as they are progressively ionized with the outer-shell electrons being stripped off. The values of the Compton profiles presented here can be used to deduce doubly differential cross-sections of variously ionized atoms colliding with other atoms and ions. The single-electron radial wavefunctions were obtained from the Hartree–Fock atomic model. Compton profiles of neutral atoms, available in the literature, are in excellent agreement with the present calculation.

X-ray diffraction patterns of NiPc in powder form show that it has a β-form with monoclinic structure. The thermal evaporation of NiPc led to α-polycrystalline films orientated preferentially to the (001) plane with an amorphous background. After annealing at 573 K for 2 h, a mixture of α- and β-phases was formed, while the conversion into β-NiPc is completed at 623 K. The dark electrical resistivity has been measured on NiPc films in the temperature range 298–423 K. Two activation energies ΔE₁ = 0.12 eV and ΔE₂ = 0.76 eV were obtained. The thermal activation energy ΔE₁ is associated with impurity conduction and ΔE₂ is associated with intrinsic conduction. Thermoelectric power measurement proved that NiPc films are p-type. The thermoelectric power curves also exhibit two different regions corresponding to extrinsic and intrinsic conductions. Room temperature J–V measurements show a linear ohmic dependence at low voltages, followed by SCLC at higher voltage levels, dominated by an exponential distribution of traps with total trap concentration of 2.79 × 10²² m⁻³.

An irreversible regenerative model of the Brayton refrigeration cycle working with an ideal Fermi gas, which is simply called the quantum refrigeration cycle, is established. Expressions for several important performance parameters, such as the coefficient of performance, work input, refrigeration load and regeneration heat, are derived, based on the equation of state of an ideal Fermi gas. The influence of quantum degeneracy of the gas, regeneration and irreversibility on the performance of the quantum refrigeration cycle is analysed comprehensively. The general performance characteristics of the cycle are revealed. Moreover, two special cases are discussed and compared in detail. Consequently, the importance of regeneration in the cryogenic refrigeration is expounded from theory. Finally, the performance of the Brayton refrigeration cycle at high temperatures is directly deduced.

A generalized form of higher-order nonlinear Schrödinger equation with varying coefficients describing dispersion-management or soliton control is presented in this paper. The exact bright and dark soliton-like solutions are given analytically. As an example, we present a dispersion decreasing system and then investigate the pulse evolution characteristics by a split-step Fourier method.

Adopting the framework of the generalized q-deformed Heisenberg–Weyl algebra , we present a mathematical procedure which leads us to obtain analytical expressions for a general class of q-deformed coherent states associated with the different patterns of the energy spectrum exhibited by the nonlinear f-oscillator. In particular, we establish the properties of a small group of q-deformed coherent states for α > γ > 0 with emphasis on the resolution of unity. As an application of these properties, we investigate the Robertson–Schrödinger uncertainty relation and the squeezing effect for the deformed coordinate and momentum operators, which are defined in terms of the abstract elements of this algebra. Furthermore, we also obtain the Wigner function and the correct quantum-mechanical marginal distributions in phase space.

Epidemic propagation within socially interacting mobile individuals is investigated on a two-dimensional (2D) square lattice. The influence of these parameters (the automata density δ, the jumping probability p, etc) on epidemic spreading is studied, and the critical jumping probability p_c and the critical population density δ_c are observed. Moreover, we establish the mean-field (MF) equations which are in good agreement with our network model. Here the efficient contact rate λ is not a constant but a function of the population density δ, the point is different with conventional MF equations. Through an approximate equivalence relation between network model and MF equations, the concrete form λ = f(δ) is obtained.

A new scheme for realizing a nonadiabatic conditional geometric phase shift via a noncoplanar (coiled) fibre system is presented. It is shown that the effective Hamiltonian that describes the interaction of polarized photons with a fibre medium is just the Wang–Matsumoto type of Hamiltonian. This, therefore, means that the coiled fibre system may be an ideal implementation for realizing the nonadiabatic geometric phase gates involved in the topological quantum computation. A remarkable feature of the present method is that it can automatically meet the conditions and requirements proposed in the Wang–Matsumoto nuclear magnetic resonance (NMR) scheme: specifically, (i) in the coiled fibre system, the dynamical phase of photon wavefunction caused by the interaction Hamiltonian automatically vanishes; (ii) the Wang–Matsumoto requirement for the parameters in the Wang–Matsumoto NMR Hamiltonian can be exactly satisfied automatically in such a fibre system; and (iii) the conditional initial state can be easily achieved by manipulating the initial wave vector of polarized photons.

La_0.85Sr_0.015MnO_3–δ (LSMO)/Fe heterostructure has been deposited on Si (100) substrate by magnetron sputtering. The results concerning the heterostructure in current perpendicular-to-plane geometry are reported. The sample exhibits a semiconductor-type conduction as the temperature is increased. Laser irradiation induces transient photoconductivity effects. These can be attributed to the disordered characteristic due to the oxygen deficiency in the film and the interface between the Fe and LSMO.

In a bounded plasma system, the plasma reorganizes itself to attain an equilibrium state through ambipolar flows. Conventional understanding of the collisional presheath is that it is the result of ambipolar processes, which establish a time-independent plasma sheath potential profile. The associated steady-state electric field accelerates the ions to the ion-acoustic speed at the main Debye sheath entrance. The inadequacy in this mechanism is that it fails to explain the observation of the excess energy transmission factors for electrons and ions. Another more likely mechanism which can be invoked is that both collisional and collisionless presheaths are sustained partially by the collective process of ion-acoustic waves (IAWs). It is possible that the turbulent development of an IAW will yield not only particle fluxes of the right value, but also energy fluxes of the observed anomalous value. The first step in proceeding with this idea is to investigate the linear response of IAWs in a generalized collisional, source-driven, plasma presheath. Matrix formulation under eigenvalue treatment has been used for linear eigenmode characterization of the acoustic-wave propagation in the presheath region.

The present work illustrates the effect of the different heating rates on the intensity and peak area of thermoluminescence (TL) glow peaks. In this work, we suggest that the kinetic equations for the TL intensity in their time-dependent forms I(t) are not adequate for comparison with experimental results I(t), where the TL is recorded versus temperature. The present work suggests that in the case of TL experiments, the first-order kinetics equation, I(t) = −dn/dt = nS exp(−E/kT), as well as the second- and general-order kinetics equation should be replaced by I(T) = −dn/dT = (nS/β) exp(−E/kT), and a similar change should be made in the second- and general-order case. Also, the present work distinguishes between the decrease in the intensity and the stability of the area of TL glow peaks as a result of increasing heating rates and the decrease in both the intensity and area of TL glow peaks as a result of thermal quenching with increasing heating rates. The present work illustrates the effect of changing the heating rate on the characterization of experimental glow curves of BeO (thermalox) for different heating rates.

We present the rules of electron correlation energies for RgX (Rg = Kr, Xe, X = Br, I) van der Waals (vdW) complex systems at CCSD(T) theoretical level with SDB-cc-pVQZ basis set by the Gaussian 98 program. A new method to derive the dispersion coefficient C₆ by fitting the intermonomer electron correlation energies to C₆R⁻⁶ function is introduced. The present C₆ values are compared with the corresponding theoretical ones.

It is well known that an external applied magnetic field can induce a phase transition from the superconducting to the normal phase at a critical temperature in a very wide range of materials. The usual practice in theoretical analyses is to assume that the applied magnetic field is uniform across the dimensions of a sample. However, in reality, even in the most refined experimental settings, the applied magnetic field will exhibit some degree of spatial inhomogeneity. In view of this, the calculation of the parallel critical field of a bulk type II superconductor hosting a hole and subjected to a spatially inhomogeneous magnetic field is reconsidered. The main aim of this investigation is to evaluate the effects of the degree of spatial inhomogeneity of the applied magnetic field on the nature of nucleation of superconductivity near a cylindrical cavity.

A simple transformation technique is used to reduce the nonlinear wave equation, the coupled Klein–Gordon–Zakharov (CKGZ) equations, the generalized Davey–Stewartson (GDS) equations, the Davey–Stewartson (DS) equations and the generalized Zakharov (GZ) equations to the elliptic-like equation. Then, their new solutions are derived using a property of the reciprocal Weierstrass elliptic function. By using the relationship between the Weierstrass elliptic functions and the Jacobian elliptic functions, new Jacobian elliptic function solutions and degenerate solutions in terms of solitary wave solutions to this class of nonlinear partial differential equations have been obtained.

In this work, a new method of measuring the thermal conductivity coefficient (κ) at high temperatures is presented. It is shown that by expressing the thermal distribution along the sample as a series, it is possible to determine κ by measuring the temperature at two points of the sample.

A new set of nonlinear equations governing the dynamics of low-frequency electrostatic drift waves in a self-gravitating electron–positron–ion (e–p–i) magnetoplasma with equilibrium density, temperature, magnetic field and velocity gradients has been derived. It is shown that possible stationary solutions of the nonlinear equations can be represented in the form of dipolar and tripolar vortices of gravitational potential. The results of the present investigation are useful to understand the nonlinear dynamics of low-frequency gravitational-drift waves in laboratory and astrophysical e–p–i magnetoplasmas.

The advances in recent years in the field of molecular dynamics are numerous and impressive. In sophisticated experimental and theoretical studies it is nowadays possible to steer chemical reactions with quantum-number-prepared molecules, to study reaction products fully state-specifically, and to derive accurate potential energy surfaces with the goal of determining the pathways along which molecular interaction can take place. Both experimental and theoretical techniques have rapidly improved, and our understanding of the dynamical nature of chemical processes is continuously growing.

In this special issue of CAMOP/Physica Scripta we have tried to present a snapshot of the state-of-the-art in the field of molecular dynamics. It contains a collection of papers submitted in association with the most recent MOLEC meeting (MOLEC XV) held in September 2004 in Nunspeet, The Netherlands. This biannual meeting started in 1976 in Trento and was subsequently organized in Brandbjerg Højskole (Denmark, 1978), Oxford (UK, 1980), Nijmegen (The Netherlands, 1982), Jerusalem (Israel, 1984), Aussois (France, 1986), Assissi (Italy, 1988), Bernkastel-Kues (Germany, 1990), Prague (Czech Republic, 1992), Salamanca (Spain, 1994), Nyborg Strand (Denmark, 1996), Bristol (UK, 1998), Jerusalem (Israel, 2000) and Istanbul (Turkey, 2002). Within the philosophy of CAMOP we have asked invited speakers to report on outstanding problems in their particular field. This comprises discussion of open questions, important applications, new theoretical and experimental approaches and also predictions of future developments. A good comment, in addition to being an authoritative contribution of an acknowledged expert, should also be readable by the non-expert and we have taken special care that the work presented here is introduced in an understandable way and has been placed within the context of accessible literature for the interested reader.

The sequence of 16 papers that is presented in this issue is arranged according to three main topics that form a focus within the field and can be roughly summarized as induced chemical (intermolecular) dynamics, molecular spectroscopy/theory, and photo-induced uni-molecular (intramolecular) dynamics.

The issue opens with a contribution by the MOLEC XV award winner Levine and his co-workers (the paper by Kornweitz et al) in which they speculate on the possibility of probing electronic rearrangement in a chemical collision using light emitted during the very collision. Banares and co-workers continue with an overview on what is and what is not understood about the dynamics of the `most simple reaction' H + H₂ and prospects for future research of this prototypic system are presented. The effect of molecular structure on chemical dynamics is discussed by Pearce et al on the example of HCl originating from Cl atoms reacting with different organic ethers. Stereodynamical effects are discussed by Cappelletti and co-workers starting from collisional alignment in supersonic seeded molecular beams with applications ranging from (in)elastic events to selective surface scattering experiments. A laboratory controlled study of chemical reactions under interstellar conditions using temperature variable multi-electrode traps is reviewed by Gerlich and Smith. Eritt et al discuss a technique capable of studying the interaction of electrons with size selected molecular ions and results are presented for the electron detachment of C_n- and Al_n-clusters. Ultrafast dynamical events at a conical intersection are discussed in a theoretical study by Burghardt et al and the experimental tools to study electron dynamics are presented by Vrakking in a contribution on direct and indirect methods to generate attoseconds.

In four spectroscopic and theoretical contributions the latest findings are presented in interpreting and understanding complicated molecular spectra. Meerts and Smit introduce a powerful numerical assign and analysis method based upon genetic algorithms and its performance is demonstrated on the example of dense spectra of (complexed) aromatic species. Interaction potential surface calculations of rare gases with halogens in van der Waals complexes are described by Delgado-Barrio and co-workers, and Tennyson discusses new theoretical techniques based on the use of the variational principle to guide the spectral assignment of complicated water spectra, e.g. at very high temperatures. Finally, Okumura and co-workers present NIR spectra of NO₃ and in combination with new calculations these shed light on how to interpret vibronic couplings in this interesting system.

The last section of this issue comprises fragmentation and photo-dissociation studies. Rubio-Lago et al discuss methods to produce high-density spin polarized hydrogen following photodissociation experiments. The photodissociation of HCl and Cl₂ is taken as an example by Balint-Kurti et al to demonstrate how amplitudes and phases of the photofragmentation matrix elements are derived from experimental measurements. Directional dynamics in photodissociation processes and the derivation of molecular frame properties are discussed in detail by Van den Brom et al using laboratory oriented molecules. And the issue closes with a contribution by Chambreau et al on different reaction mechanisms in the photodissociation of formaldehyde into H₂ and CO.

Coming to the end of this editorial, we wish to thank all the authors who participated with their contributions in this issue. It shows what is possible nowadays in the field of molecular dynamics and where things are heading in the near future. We thank Physica Scripta for providing us with the platform for this Special Issue, and we wish you, dear reader, many new insights!

Steven Solte, Vrije Universiteit Amsterdam, The Netherlands Harold Linnartz, Leiden Observatory, The Netherlands

During a chemical reaction the electronic structure of the reactants reforms to the structure of the products. In the simplest case, an old bond is broken and simultaneously a new bond is formed. Even when this change occurs adiabatically, meaning that the electronic charge distribution tracks the motion of the nuclei without change in its quantum state, there is a displacement of charge, particularly so if there is a switch from a covalent to an ionic bonding. This reorganization can be probed by light emitted during the very collision. The F + H₂ reaction is used as a computational example.

This paper focuses on recent progress in the understanding of the H + H₂ reaction and its isotopic variants. The detailed agreement between theory and experiment attained during the last years is emphasized and major experimental and theoretical advances are highlighted. The excellent description of most experimental findings, from state-resolved cross-sections to thermal rate constants, provided by the available quantum mechanical (QM) treatments, as well as the good overall behaviour of classical mechanics are underlined. Debated issues on short-lived complexes and delayed scattering, resonances and interferences, geometric-phase (GP) effects, or product rotational distributions are discussed. Finally, some prospects for future research on this prototypic system are presented.

The reactions of Cl atoms with three organic ethers, dimethyl ether (CH₃OCH₃), oxirane (c-C₂H₂O) and oxetane (c-C₃H₆O) provide an opportunity to study the effects of different molecular structural motifs on the chemical dynamics. The rotational excitation of the nascent HCl reaction product has been measured for all three reactions, and the results are compared with direct dynamics trajectory calculations that allow mechanisms to be visualized with the aid of trajectory animations. Reaction of oxirane, a strained, three-membered ring compound, gives rise to HCl that is markedly rotationally cooler (T_rot = 168 ± 7 K) than the products of the two other reactions (T_rot = 418 ± 25 K for Cl + dimethyl ether and 399 ± 23 K for Cl + oxetane). Possible reasons are discussed in terms of the reorientational dynamics of the polar HCl and organic radical products in the post-transition state regions of the reaction potential energy surfaces.

Production, characterization and control of alignment degree of molecules are of importance for investigating in detail the stereodynamics of elementary processes involving elastic, inelastic and reactive events and also to prepare gas-phase species for selective surface scattering investigations. The focus here is on collisional alignment in supersonic seeded molecular beams, a technique which shows perspectives on the applications, offering appealing features for 'duty cycle' and intensity characteristics. Attention will be addressed to recent stereodynamical studies carried out on hydrocarbon molecules in the gas phase and on applications of such aligned beams to surface scattering studies.

In this paper, we outline recent developments in and the growing need for laboratory astrochemical measurements. After a short review on experimental methods, we focus primarily upon the utility of multi-electrode ion trapping methods for addressing key problems in reaction dynamics and their applications towards gaining a better understanding of the physicochemical driving forces behind compositional development in interstellar and circumstellar environments. Temperature variable trapping techniques, combined with lasers and molecular beams are unique tools for studying state specific reactions, for ion spectroscopy and for investigating the structure and stability of complex charged objects as a function of their internal energy. Particular emphasis is given to reactions with hydrogen atoms and molecules, H–D exchange leading to isotopic fractionation, problems in hydrocarbon ion chemistry and association chemistry in rarefied environments. In the outlook, we discuss the future needs in astrochemistry in order to pave the way towards understanding the next generation of sophisticated astronomical observations and to prepare for them.

The interaction between size specific negative clusters (C_n⁻, 1 < n < 12, Ag_n⁻, 1 < n < 11) and low-energy electrons has been studied using a new experimental setup where the ionic clusters are first cooled to room temperature in an electrostatic ion trap. The electron impact detachment cross-sections were measured for electron energies between 5 and 30 eV. The results are analysed in terms of a classical model.

The recent development of attosecond laser pulses through high-harmonic generation and their characterization using a variety of cross- and auto-correlation techniques has opened up the possibility to study electron dynamics in chemical and physical processes on their natural timescales. In this paper we review how electrons exposed to strong electric fields are at the basis of the generation of high-harmonics and may provide model systems for the application of attosecond laser pulses.

We review some of the concepts which we have recently developed in order to describe the influence of an environment on the ultrafast dynamical events at a conical intersection (CI). In particular, we propose a description in terms of effective environmental modes, which accurately account for the short-time dynamics at the conical intersection. We address the construction of these modes (i) for intramolecular situations, where the modes in question result from an orthogonal coordinate transformation for the overall N-mode system, and (ii) for solute–solvent interactions in polar solvents, where a description in terms of a Marcus-like solvent coordinate is obtained. In both cases, the dynamical process is determined by the combined evolution of the internal molecular modes and the environmental coordinates, on an ultrafast timescale. We discuss examples related to an intramolecular multi-mode situation in pyrazine, and the polar solvation dynamics for protonated Schiff bases.

This paper describes a numerical technique that has recently been developed to automatically assign and fit high-resolution spectra. The method makes use of genetic algorithms (GA). The current algorithm is compared with previously used analysing methods. The general features of the GA and its applications in automated assignments is discussed. In a number of examples the successful application of the technique is demonstrated.

The spectrum of water is ubiquitous and therefore the demand for a reliable theoretical model for it remains pressing. The treatment of nuclear motion using methods based on the variational principle has led to a major advance in the development of the model but places great emphasis on the accurate treatment of the underlying potential energy surface. Progress in constructing high-accuracy potentials both ab initio and by fitting to spectroscopic data is discussed.

In this review we report on interaction potential surface calculations of Rg–XY (Rg = rare gas and X, Y = halogens) van der Waals (vdW) complexes. Experimental data available on the structure and dynamics of such systems mainly originate from the B ← X excitation spectroscopy and, therefore, potential surfaces for both electronic states involved are required for the theoretical treatments. Hence, ab initio technology is used at the coupled-cluster (CCSD(T)) level of theory for constructing these surfaces. Relativistic effects are included with the use of large-core pseudo-potentials for the halogen atoms, while efficient augmented correlation-consistent polarized basis sets are employed for the Rg ones, to ensure saturation in interaction energies in the highest level of electron correlation treatment. For all ground state Rg–dihalogen systems studied, the potential surface shows minima for both linear and T-shaped orientations. In contrast, the potential surfaces of the electronically B excited state complexes present T-shaped minimum. Variational calculations for both electronic potentials are performed to calculate the bound states of the ground and B excited vdW complexes, and binding energies, vibrationally averaged structures and spectral shifts are determined. Here, an application of the present methodology on the ground X and B excited HeI₂ conformers is reported and the obtained results are discussed in terms of available experimental data.

The recent cavity ringdown (CRD) measurement of the forbidden transition of the nitrate radical NO₃ reveals a rich, well-resolved spectrum in the near-infrared. The spectroscopic detail provides a new window onto the Jahn–Teller (JT) and pseudo-Jahn–Teller (PJT) effects in NO₃. This paper reviews the current experimental evidence for vibronic coupling in the à state and discusses the theoretical issues in the context of new preliminary EOMIP/CCSD and CCSD(T) calculations. The theoretical results to date indicate that the Ã ²E'' state of NO₃ undergoes a relatively strong JT distortion which may require inclusion of higher order vibronic couplings. The intensity of this transition may involve multiple intensity borrowing mechanisms via PJT coupling among the , and states.

We discuss how nuclear spin can be highly polarized from the transfer of molecular rotational polarization via the hyperfine interaction, and how large atomic electronic polarization can be produced via molecular photodissociation with polarized light. In combination, these two pulsed-laser techniques can be used to produce highly polarized atoms at densities close to the density of the parent molecules. We compare these methods to existing methods for producing polarized atoms and present specific examples.

Amplitudes and phases of the photofragmentation T matrix can be determined from experiment by measuring the vector correlation coefficients of the photofragments. Comparison of the experimentally obtained data with the results of quantum mechanical calculation allows the realization of the complete experiment in the field of molecular photodynamics. Selected studies where this analysis has been carried out are discussed.

We review how molecular frame directional properties can be extracted from the photodissociation of laboratory-oriented molecules. Molecules can be hexapole state-selected and spatially oriented in the electric field of a velocity-map imaging lens. The oriented molecules are dissociated with the linear polarization set at a chosen angle to the orientation direction of the molecules. The angular distribution of photofragments is measured using the velocity-map imaging technique. From the observed asymmetry in the laboratory frame, we can directly extract the molecular frame angles between the final photofragment recoil velocity and the permanent dipole moment and the transition dipole moment. We discuss the photodissociation of oriented chiral molecules and show how the combination of laboratory orientation and selective laser excitation leads to a three-dimensional oriented, 'fixed-in-space', molecule in the excited state. From the recoil distribution in the laboratory frame, direct detailed molecular frame angular correlations can be extracted.

We present a state-correlated experimental investigation of formaldehyde (H₂CO) dissociation to H₂ and CO following excitation to a series of vibrational bands in the first electronically excited state, S₁. The CO was detected by resonance-enhanced multiphoton ionization at various rotational states of CO (J = 5–45) and the CO velocity distributions were measured using state-resolved DC Slice Imaging. These high-resolution measurements reveal the internal state distribution of the correlated H₂ cofragments. The results show that the rotationally hot CO (J_CO = 40) is produced in conjunction with vibrationally cold H₂ fragments (ν = 0–3), consistent with dissociation through the celebrated skewed transition state. After excitation of formaldehyde at energies near and above the threshold for dissociation to radical products (H₂CO → H+HCO), a second molecular elimination channel appears which is characterized by rotationally cold CO (J ̃ 5–15) correlated with highly vibrationally excited H₂ (ν = 5–7). These products are formed through a novel roaming H-atom mechanism that involves intramolecular H abstraction and avoids the region of the transition state to molecular elimination entirely. The current measurements give insight into the energy dependence of the branching of these different reaction mechanisms.

Physica Scripta is an international physics journal published for the Royal Swedish Academy of Sciences on behalf of the Nordic Science Academies and Physical Societies. This issue marks the beginning of the partnership between the Royal Swedish Academy of Sciences and Institute of Physics Publishing (IOP). We look forward to a fruitful relationship in which Physica Scripta can profit from the international reach of IOP. Authors and readers will benefit from advance publication of articles on the web prior to receiving each month's journal issue.

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