Table of contents

This year has been a very active one for Journal of Physics B: Atomic, Molecular and Optical Physics (J. Phys. B). As well as sponsoring a number of lectures at various conferences the journal also sponsored a number of poster prizes. The first sponsored poster prizes were awarded at the 23rd International Conference on Photonic Electronic and Atomic Collisions (ICPEAC, http://atomlx04.physto.se/~icpeac/index.html) held in Stockholm, Sweden. This was the second time the poster sessions had been sponsored by J. Phys. B and there was great interest in all of the posters presented on each of the five day sessions.

Later in the year J. Phys. B sponsored the poster prizes awarded at the very first National Quantum, Atomic, Molecular and Plasma Physics meeting (QuAMP, http://physics.open.ac.uk/quamp/) held at the Open University, Milton Keynes, UK. The prize posters at this conference were presented over a three-day period and reflect the breadth of research presented at this meeting. The winners from each conference are listed below (the presenter of each poster is highlighted in bold where there is more than one author).

All the prize posters were of a very high standard and the presenters of each poster were also commended on their ability to present their work clearly. We would therefore like to extend our congratulations to all of the winners once again and to thank the organizers for all their help in arranging the sponsorship. Both conferences were very lively, well organized and enjoyed by all the delegates. We were very pleased that J. Phys. B was able to continue its relationship with ICPEAC for the second time and that we were involved with the inaugural meeting of QuAMP!

We would also like to take this opportunity to extend our thanks to all of our authors, readers and referees for their support and contribution to J. Phys. B throughout 2003, and we look forward to working with you in 2004.

Season's Greetings from the J. Phys. B publishing team!

ICPEAC 2003 Poster Prize winners

Electron/positron scattering by positronium S Gilmore, J E Blackwood and H R J Walters

Forward-electron spectroscopy in the ESR S Hagmann, Th Stöhlker, R Moshammer, J Ullrich, R Dörner, Ch Kozhuharov, F Bosch, H Rothard, H Schmidt-Böcking, A Gumberidze, D Banaś, G Laczko, U Spillmann, St Tashenov, M Steck, P Beller, F Nolden, R Steiner, P Spiller, M Nofal and R Mann

Multiple electron-impact ionization of Sc⁺ ions J Jacobi, H Knopp, S Schippers, W Shi and A Müller

Polarization studies for radiative electron capture into high-Z ions S Tachenov, Th Stöhlker, D Banaś, H F Beyer, F Bosch, A Gumberidze, S Hagmann, Ch Kozhuharov, Th Krings, X Ma, A Oršić Muthig, D Protic, D Sierpowski, U Spillmann, Z Stachura and A Warczak

Multiplet resolved N 1s photoelectron angular distributions from the fixed-in-space NO molecules K Hosaka, J Adachi, M Takahashi and A Yagishita

QuAMP 2003 Poster Prize winners

Intuitive coherent control of molecular Rydberg wavepackets R Minns and R Patel

The design and simulation of a novel 'cusp' based electron beam source E Rafferty

Study of ultrashort, high intensity laser–matter interaction via proton imaging S Kar

Experimental analysis of an astrophysical cyclotron maser instability D Speirs

Core magnetic reconnections in spherical tokamaks G Turri

Aspects of dust in fusion plasmas J Martin

We consider the interaction of atoms with a pulse of a linearly polarized electric field consisting of two phase-locked frequencies whose ratio ω_H/ω_L is the ratio of arbitrary integers h/l, with h>l. If the electric amplitudes vary in time, they do so with the same slow envelope. The relative phase can be used as a control parameter via variation of the phase ϕ_H of ω_H or ϕ_L of ω_L. We derive the physically important ranges of relative phase for total-yield processes as a function of h:l; they depend on whether h,l are both odd or only one is odd. We tabulate a variety of relevant phase-dependent results for all h:l from 2:1 through 8:7. We use calculations and experimental data for helium and hydrogen Rydberg atoms driven by a bichromatic microwave field to confirm the physically important ranges of ϕ_H and ϕ_L for a few h:l ratios. Two experimental examples taken from the literature for the interactions of atoms with sub-picosecond, bichromatic laser pulses also confirm our conclusions.

Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 47 levels of the astrophysically important ion Sm¹⁺ over the energy range 21 000–36 000 cm⁻¹. The new results have been compared with previous measurements but also with theoretical calculations taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for many levels of this complex ion. New calculated transition probabilities are deduced from the experimental lifetimes and from the theoretical branching fractions for 162 transitions of astrophysical interest. These results will help astrophysicists in the quantitative investigation of the chemical composition of CP stars.

Accurate energies and oscillator strengths for seven lowest excited states of neon-like ions from Na II to Ar IX are calculated using a mixed configuration-interaction and perturbation-theory approach. The energies obtained are in close agreement with experiment. Our oscillator strengths are compared with experiments and other theories.

A model-potential approach successfully employed in the past for describing potential curves of light alkali dimers is extended to calculate potential curves of Σ symmetry for the heavy molecular ions Rb₂⁺, Cs₂⁺ and RbCs⁺. The results are in agreement with those calculated using a pseudopotential method, except for the Cs⁺+Cs(5d) dissociation limit. The limits of the present model-potential calculations and the ways of improving them are carefully analysed.

We have investigated proton emission from dissociated H₂ molecules after colliding with H⁺ and He²⁺ ions with energies 25, 50 and 100 keV amu⁻¹. The energy spectra of protons have been obtained covering the angular range from 10° to 170° and fragment energies from 3–15 eV for He²⁺ projectiles and in the 0–15 eV range for H⁺ impact, respectively. Using the Franck–Condon approximation we were able to find the relative contributions for some dissociation channels (2p π_u, 2s σ_g, 2p σ_u and Coulomb explosion (CE)). For He²⁺ projectiles we found that the momentum transfer to the target must be included in the model to obtain a better description of the experimental results. When compared to the H⁺ impact case, we observe for He²⁺ projectiles the enhancement of the CE channel due to higher capture probabilities. Differential cross sections as a function of emission angle were obtained to investigate the orientation dependence of the electronic processes leading to dissociation. Total cross sections are also estimated and compared to measurements from other laboratories.

We present results of microwave and millimetre-wave resonance measurements in D, F and G Rydberg states of neutral aluminium in the frequency range 4–423 GHz for principal quantum numbers n = 22–43. In all, 12, 27 and 19 resonances of or , or and or series, respectively, have been recorded. D-state fine-structure doublet splittings have been obtained with accuracy ± 1.4 MHz. For D and G states, quantum defect Ritz-expansion parameters have been determined, from which the Rydberg series can be accurately reconstructed to an accuracy of order ± 1 MHz (3 × 10⁻⁵ cm⁻¹) for all n.

Natural orbital expansions are considered for highly accurate three-body wavefunctions written in the relative coordinates r₃₂, r₃₁ and r₂₁. Our present method is applied to the ground S (L = 0) -state wavefunctions of the Ps⁻ and ions. Our best variational energies computed herein for these systems are E(Ps⁻) = −0.262 005 070 232 980 107 7666 au and  au, respectively. The variational wavefunctions determined for these systems contain between 2000 and 4200 exponential basis functions. In general, the natural orbital expansions of these functions are compact and rapidly convergent functions, which are represented as linear combinations of some relatively simple functions. The natural orbitals can be very useful in various applications, including photodetachment and scattering problems.

Single-electron excitation in He⁺–He collisions is investigated in the 30–50 keV range, where the excitation cross-sections have resonance-like maxima. By measuring anticrossing spectra, we show that the levels of He I with are populated effectively and coherently in this energy range. The superposition states of the excited electron resulting from the collision process are identified as the parabolic Stark states with the largest electric dipole moments. The results are explained with the Paul-trap model and saddle dynamics.

The absolute total cross section (TCS) for electron scattering from hexafluoro-1,3-butadiene (1,3-C₄F₆) was obtained in a transmission experiment for electron impact energies from 0.6 to 370 eV. The TCS energy function has two pronounced enhancements separated by a deep minimum located near 2.6 eV: a low-energy hump around 1 eV and a dominant very broad enhancement centred near 30 eV. The 1,3-C₄F₆ TCS results are compared with the data for hexafluoro-2-butyne (2-C₄F₆) and the influence of the structural differences on the electron-scattering TCS for isomers of the C₄F₆ molecule (isomeric effect) is explicitly indicated. The most pronounced role of the molecular geometry on the magnitude and shape of the TCS energy dependence is observed at the lowest energies studied. Above 40 eV the TCSs for both isomers are close to each other. Some conformities of TCSs within a series of perfluorocarbons (C₂F₄, 1,3-C₄F₆, C₆F₆) as well as in a series of their hydrocarbon counterparts (C₂H₄, 1,3-C₄H₆, C₆H₆) are also pointed out and discussed.

Coplanar symmetric (e,2e) results are presented for the ionization of calcium by electron impact. The incident electron energy was varied from 10.1 to 64.6 eV, the outgoing electrons sharing the excess energy equally. The experimental results show a complex variation in the magnitude of the cross- section as a function of energy and angle. At the highest incident energy, the cross-section varies by almost five orders of magnitude. At the lowest energy, evidence of post-collisional interaction between the outgoing electrons can be seen, although the magnitude of this effect is small.

Atomic collision parameters have been derived for electron impact excitation of calcium using the superelastic scattering method, at incident energies equivalent to 20, 25 and 35 eV. The pseudo-Stokes parameters for the superelastic process were determined, and the parameters P_lin⁺, , γ⁺ and P_tot⁺ derived for the 4 ¹P₁ state. The results are compared to a relativistic distorted-wave approximation (RDWA) theory, and to previous experimental results. At the highest incident energy the results presented here compare well with theory, but at the lowest energy, significant disagreement between theory and experiment is observed.

Since the above paper was published we have received a suggestion from T K Rebane that our variational energy, -402.261 928 652 266 220 998 au, for the 3S(L = 0) state from table 4 (right-hand column) is wrong in the fourth and fifth decimal digits. Our original variational energies were E(2000) = -402.192 865 226 622 099 583 au and E(3000) = -402.192 865 226 622 099 838 au. Unfortunately, table 4 contains a simple typographic error. The first two digits after the decimal point (26) in the published energies must be removed. Then the results exactly coincide with the original energies. These digits (26) were left in table 4 from the original version, which also included the 2S(L = 0) states of the helium-muonic atoms.

A similar typographic error was found in table 4 of another paper by A M Frolov (2001 J. Phys. B: At. Mol. Opt. Phys.34 3813). The computed ground state energy for the ppµ muonic molecular ion was -0.494 386 820 248 934 546 94 mau. In table 4 of that paper the first figure '8' (fifth digit after the decimal point) was lost from the energy value presented in this table.

We wish to thank T K Rebane of the Fock Physical Institute in St Petersburg for pointing out the misprint related to the helium(4)-muonic atom.

The PDF file provided contains web links to all articles in this volume.