Chapter Three - Atomic, Molecular, and Optical Physics in the Early Universe: From Recombination to Reionization

The Journal of Physics B: Atomic, Molecular and Optical Physics Editorial Board has reassessed the purpose of a Letter to the Editor. This follows a discussion by the Board that highlighted the change in the way that the community uses Letters. Originally the idea of a Letter was to publish urgent work that required a follow-up paper containing more details. However, increasingly, authors are using Letters as a way to publish small amounts of work that they feel requires fast publication but does not necessarily require a follow-up paper. The Board believes that the definition of a Letter has become very blurred and needs to be redefined.

This year marks the 125th anniversary of the founding of The Physical Society of London and its Proceedings, which were launched in 1874, from which the Journal of Physics, and later J. Phys. B: At. Mol. Opt. Phys., originated. In contrast, synchrotron radiation was discovered just over 50 years ago [1]. However its first systematic scientific application, which was in the field of atomic and molecular physics, occurred even more recently in 1963 when Madden and Codling performed their pioneering investigations of the absorption spectra of the rare gases in the VUV [2]. Driven in large part by the demands of atomic and molecular science, dedicated storage rings (second generation sources) soon followed, built specifically as light sources to operate from the IR to the x-ray spectral regions. The use of synchrotron radiation has now extended worldwide to over 70 research facilities in every continent of the world - many of them third-generation machines with insertion devices to enhance performance. Although the rapid increase in computational speed is often cited as a dramatic example of modern technological progress, the increase in brightness of synchrotron light sources has occurred even more rapidly [3]. Not surprisingly numerous additional scientific areas ranging from protein crystallography to materials science have also benefited greatly from this progress. The role of synchrotron radiation in research into atomic, molecular and optical physics continues to expand rapidly as experiments of ever-increasing complexity are combined with increased photon flux and fully characterized polarization. The present special issue of J. Phys. B: At. Mol. Opt. Phys. is intended to bring to the attention of its readers some aspects of current experimental, and theoretically associated, work on synchrotron based studies of molecules that relate to the field of atomic, molecular and optical physics. The research papers on experimental work published in this special issue originate from eight countries and seven synchrotron facilities. The wide range of topics covered includes photoionization processes and dynamics, valence and inner-shell photoelectron spectroscopy, photoabsorption and photofluorescence, photofragmentation and dissociative photoionization and multiple photoionization. The molecules studied range in size from hydrogen, the most abundant and simplest molecule in the Universe, up to DNA, the most important molecule in biology. Some, such as OH, are highly reactive and short-lived. Others, such as fullerene endohedrals, have only recently been discovered. Thus the articles included in this special issue cover a wide variety of exciting topics in the areas of molecular and optical physics. It is hoped, therefore, that this will further stimulate interest and appreciation of the role and importance of synchrotron radiation in the study of molecules. It is, of course, the contributors and referees who have made this thematic issue on molecular physics with synchrotron radiation possible, and they deserve our thanks and appreciation.

A novel Hamiltonian scheme for non–relativistic quantum electrodynamics in which the gauge arbitrariness of the field potential is kept explicit is used to study the gauge–dependence properties of various versions of perturbation theory when resonance and line–broadening effects are admitted. Time–dependent perturbation theory is shown to have severe gauge–dependence problems unless ad hoc modifications are made. A time–independent formulation of S–matrix theory is then studied. Far from resonance, the S–matrix is gauge invariant in all orders of perturbation theory due to a very precise cancellation of gauge–dependent terms which requires, among other things, complete sets of intermediate states; energy conservation also has a crucial role. However, an obvious separation of the S–matrix into a resonant (pole) and non–resonant background leads to incomplete cancellation of the gauge–dependent terms. The introduction of the Heitler damping matrix into an integral equation for the T–matrix leads to a gauge–invariant result. This provides the basis for a gauge invariant S–matrix theory of atoms and molecules interacting with electromagnetic radiation that encompasses resonance and damping effects.

Atomic physics has lost in Ugo Fano one of its dominant players during a good part of the 20th century. He has also steadily contributed to this journal during its entire existence as a ‘Correspondent’. One of us (HHS) was occupied for a number of years with experiments on the ‘Fano Effect’ as applied to the intensity ratio anomalies in alkali principal series. This is related to his work on production of polarized electrons by photoionization with polarized light or with polarized atoms. Another (FJdH), together with coworkers at the FOM Institute for Atomic and Molecular Physics, is indebted to Ugo Fano for his stimulation of and his continuous interest in the experiments on total and multiple ionization of noble gas atoms by electron impact. He pointed out to us the relation with photoabsorption by these atoms and the corresponding oscillator strength in the continuum according to the Bethe-Born theory. In addition, the Fano–Lichten theory, describing the promotion of electrons in quasi-molecules formed in keV heavy ion–atom collisions, has been used by us to explain inner-shell ionization and resulting x-rays.It is important to document the work and lives of eminent physicists who have made seminal contributions to atomic, molecular, and optical physics. This was done recently with the special issue of Comments on Atomic and Molecular Physics on the `Casimir Effect'. We are grateful to Mitio Inokuti and A R P Rau, long-time collaborators of Ugo Fano, for the overview of his life's work, his biography and publications.

These proceedings arose from the 7th Asian International Seminar on Atomic and Molecular Physics (AISAMP) which was held at the Indian Institute of Technology, Madras from 4–7 December 2006. The history of the AISAMP has been reviewed by Takayanagi http://www.physics.iitm.ac.in/~aisamp7/history.html. This international seminar/conference series grew out of the Japan–China meetings which were launched in 1985, the fourth of which was held in 1992 and carried a second title: The First Asian International Seminar on Atomic and Molecular Physics (AISAMP), thus providing a formal medium for scientists in this part of the world to report periodically and exchange their scientific thoughts. The founding nations of Japan and China were joined subsequently by Korea, Taiwan, India and Australia. The aims of the symposia included bringing together leading experts and students of atomic and molecular physics, the discussion of important problems, learning and sharing modern techniques and expanding the horizons of modern atomic and molecular physics. The fields of interest ranged from atomic and molecular structure and dynamics to photon, electron and positron scattering, to quantum information processing, the effects of symmetry and many body interactions, laser cooling, cold traps, electric and magnetic fields and to atomic and molecular physics with synchrotron radiation. Particular interest was evident in new techniques and the changes of the physical properties from atomic to condensed matter. Details of the 7th AISAMP, including the topics for the special sessions and the full programme, are available online at the conference website http://www.physics.iitm.ac.in/~aisamp7/. In total, 95 presentations were made at the 7th AISAMP, these included the Invited Talks and Contributed Poster Presentations, of which 52 appear in the present Proceedings after review by expert referees, refereed to the usual standard of the Institute of Physics journal: Journal of Physics B: Atomic, Molecular and Optical Physics. We received extensive support from the Journal of Physics: Conference Series staff; Graham Douglas, in particular, has been of tremendous help. The 7th AISAMP was very well attended and was sponsored primarily by the host Indian Institute of Technology, Madras (Chennai), the Board of Research in Nuclear Sciences, (Department of Atomic Energy, Government of India), the Department of Science and Technology, (Government of India), and the Asian Office of Aerospace Research and Development (AOARD) of the US Air Force. There was support from various quarters—each was invaluable and added to the success of the 7th AISAMP. We are very grateful to all the sponsors. It is superfluous to add that guidance and active participation from several colleagues within the host Institute was the primary source of strength for the actual organization of the conference and the multitude of arrangements for the organization came from the young graduate students at the IIT-Madras. We hope that this volume of Journal of Physics: Conference Series will be referenced widely and that it will strengthen ties between various countries in the region in and around Asia, and also of course to all scientists in this field the world over. Pranawa C Deshmukh, Purushottam Chakraborty and Jim F Williams Editors

Alexander Dalgarno

The different types of research classed as atomic, molecular and optical (AMO) physics have changed over the past few years. As the field of AMO physics has evolved, with researchers moving into more interdisciplinary research areas, so has J. Phys. B, evolving along with the research communities to provide a high-quality outlet for their work. J. Phys. B covers all aspects of atomic, molecular and optical physics. From the traditional studies of atomic properties to the new nanotechnology interfaces, if the system under investigation involves manipulation on an atomic or molecular level, then it will fall within the J. Phys. B scope. We currently publish articles across a wide range of research and we continue to encourage articles from newer areas relating to AMO as well as the core AMO research that we have always published in the journal.Extended scope of J. Phys. BJ. Phys. B covers all aspects of atomic, molecular and optical physics. We publish articles on the study of atoms, ions, molecules, condensates or clusters, from their structure and interactions with particles, photons, fields and surfaces to all aspects of spectroscopy. Quantum optics, non-linear optics, laser physics, astrophysics, plasma physics, chemical physics, optical cooling and trapping and other investigations where the objects of study are the elementary atomic, ionic or molecular properties of processes are also included.With the introduction of the BEC Matters! portal and IOP Select, J. Phys. B, one of the major contributors, offers authors of articles in this research area wider visibility and more flexible publication with the opportunity to display multimedia attachments or web links to key groups and results.Recent papers reflect the wide scope of J. Phys. B:Calculation of cross sections for very low-energy hydrogen-antihydrogen scattering using the Kohn variational method E A G Armour and C W Chamberlain J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 22 (28 November 2002) L489-L494Imaging the electron transfer reaction of Ne2+ with Ar using position-sensitive coincidencespectroscopy Sarah M Harper, Wan-Ping Hu and Stephen D Price J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 21 (14 November 2002) 4409-4423Ultraviolet-infrared wavelength scalings for strong field induced L-shell emissions from Kr and Xe clusters Alex B Borisov, Xiangyang Song, Fabrizio Frigeni, Yang Dai, Yevgeniya Koshman, W Andreas Schroeder, Jack Davis, Keith Boyer and Charles K Rhodes J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 21 (14 November 2002) L461-L467A Bose-Einstein condensate in an optical lattice J Hecker Denschlag, J E Simsarian, H Häffner, C McKenzie, A Browaeys, D Cho, K Helmerson, S L Rolston and W D Phillips J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 14 (28 July 2002) 3095-3110Locality of a class of entangled states I R Senitzky J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 14 (28 July 2002) 3029-3039Solitons and vortices in ultracold fermionic gases Tomasz Karpiuk, Miroslaw Brewczyk and Kazimierz Rzazewski J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 14 (28 July 2002) L315-L321Stable islands in chaotic atom-optics billiards, caused by curved trajectories M F Andersen, A Kaplan, N Friedman and N Davidson J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 9 (14 May 2002) 2183-2190Emission probability and photon statistics of a coherently driven mazer Jin Xiong and Zhi-Ming Zhang J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 9 (14 May 2002) 2159-2172The Li+-H2 system in a rigid-rotor approximation: potential energy surface and transport coefficients I Røeggen, H R Skullerud, T H Løvaas and D K Dysthe J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 7 (14 April 2002) 1707-1725The stochastic Gross-Pitaevskii equation C W Gardiner, J R Anglin and T I A Fudge J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 6 (28 March 2002) 1555-1582Oxygen ion impurity in the TEXTOR tokamak boundary plasma observed and analysed by Zeeman spectroscopy J D Hey, C C Chu, S Brezinsek, Ph Mertens and B Unterberg J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 6 (28 March 2002) 1525-1553Electron-hexafluoropropene (C3F6) scattering at intermediate energies Czeslaw Szmytkowski, Pawel Mozejko and Stanislaw Kwitnewski J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 5 (14 March 2002) 1267-1274High-resolution investigations of C2 and CN optical emissions in laser-induced plasmas during graphite ablation S Acquaviva and M L De Giorgi J. Phys. B: At. Mol. Opt. Phys. Vol 35, No 4 (28 February 2002) 795-806

As a result of reviewing several aspects of our content, both in print and online, we have made some changes for 2008. These changes are described below.Article numberingJournal of Physics B: Atomic, Molecular and Optical Physics (J. Phys B.) has moved from sequential page numbering to an article numbering system, offering advantages and flexibility for the publication process. For example, papers in special issues or sections can be published online as soon as they are ready, without having to wait for a whole issue or section to be allocated page numbers.The bibliographic citation will change slightly. Articles should be referenced using the six-digit article number in place of a page number, and this number must include any leading zeros. For instance:Surname X and Surname Y 2008 J. Phys. B: At. Mol. Opt. Phys. 41 015001Articles will continue to be published on the web in advance of the print edition.Subject sectionsJ. Phys. B has taken advantage of this new numbering scheme to introduce subject sections into which research papers are now categorized. While clarifying the scope of the journal, we hope that the journal content will become more readily accessible to our readers.The subject sections are listed as follows: Atomic Physics Molecular Physics and Clusters Atomic and Molecular Collisions Cold Matter Optical and Laser Physics Quantum Optics, Information and Control Ultrafast, High-Field and X-Ray Physics Astrophysics and Plasma Physics To find out to more information on the subfields associated with these subject sections, please follow link.A new look and feelJ. Phys. B has moved from B5 (176 × 250 mm) single-column format, to approximate US Letter size (210 × 286 mm) double-column format. We believe that this change will benefit our readers by having them save paper when printing articles from the online journal and consequently it will help protect the environment.Last, but not least, we have taken the opportunity to refresh the design of the journal cover to create a consistent look and feel across IOP Publishing's range of publications. We hope you like the new cover.If you have any questions or comments about any of these changes, please contact us at jphysb@iop.org

The nature of the first generation of stars in the universe remains largely unknown. Observations imply the existence of massive primordial stars early in the history of the universe, and the standard theory for the growth of cosmic structure predicts that structures grow hierarchically through gravitational instability. We have developed an ab initio computer simulation of the formation of primordial stars that follows the relevant atomic and molecular processes in a primordial gas in an expanding universe. The results show that primeval density fluctuations left over from the Big Bang can drive the formation of a tiny protostar with a mass 1% that of the Sun. The protostar is a seed for the subsequent formation of a massive primordial star.

Advances in Atomic, Molecular, and Optical Physics

The current consensus is that galaxies begin as small density fluctuations in the early Universe and grow by in situ star formation and hierarchical merging. Stars begin to form relatively quickly in sub-galactic-sized building blocks called haloes which are subsequently assembled into galaxies. However, exactly when this assembly takes place is a matter of some debate. Here we report that the stellar masses of brightest cluster galaxies, which are the most luminous objects emitting stellar light, some 9 billion years ago are not significantly different from their stellar masses today. Brightest cluster galaxies are almost fully assembled 4-5 billion years after the Big Bang, having grown to more than 90 per cent of their final stellar mass by this time. Our data conflict with the most recent galaxy formation models based on the largest simulations of dark-matter halo development. These models predict protracted formation of brightest cluster galaxies over a Hubble time, with only 22 per cent of the stellar mass assembled at the epoch probed by our sample. Our findings suggest a new picture in which brightest cluster galaxies experience an early period of rapid growth rather than prolonged hierarchical assembly.

Advances in Atomic, Molecular, and Optical Physics

Call for papers The achievement of Bose-Einstein condensation using evaporative cooling has driven a new generation of atomic, molecular and optical physics. It has also given rise to important new links with other areas of physics. The Journal of Physics B will have a special issue to highlight the important new science that is coming out of the production of ultra-cold trapped gases. This should, of course, include the production, manipulation and use of matter waves. Papers that address related topics in atom optics and interferometry are very much welcomed. Coverage: Bose-Einstein Condensation Ultra-cold Atomic Collision Physics Atom Lasers Josephson Effects Degenerate Fermi Gases Atomic Optics and Interferometry Nonlinear Atom Optics Molecular Physics in Condensed Gases Phase Coherence of Condensates Vortices and Solitons in condensates All Optical Routes to BEC Submission Authors are invited to submit articles for consideration in the Special Issue, scheduled for publication in November 2000. All articles will be refereed to the usual high standards of the journal, and authors will receive free offprints of their published paper. There are no page charges. Three copies of the manuscript are required and should be sent to the Publishing Editor of the Journal at the address given below. Please include a covering letter stating that the submission is to be considered for the Coherent Matter Waves Special Issue. If this is not included the article will be treated as a normal submission and will not appear in the dedicated issue. Deadline for submission of manuscripts is 14 April 2000. Please send manuscripts to: Nicola Gulley Publishing Editor, Journal of Physics B: Atomic, Molecular and Optical Physics Dirac House, Temple Back, Bristol, BS1 6BE, UK. Tel: 44 (0) 117 930 1141 Fax: 44 (0) 117 929 7481 Email: jphysb@ioppublishing.co.uk Further details may be obtained from: Keith Burnett Honorary Editor, Journal of Physics B: Atomic, Molecular and Optical Physics Department of Physics, Clarendon Laboratory University of Oxford, Parks Road, Oxford, OX1 3PU, UK. Email: k.burnett1@physics.ox.ac.uk

The origins of matter and radiation in the universe lie in a hot big bang. We present a number of well-motivated cosmologies in which the big bang occurs through a strong first-order phase transition---either at the end of inflation, after a period of kination (``kination-induced big bang''), or after a second period of vacuum domination in the early Universe (``supercooled big bang''); we also propose a ``dark big bang'' where only the dark matter in the Universe is created in a first-order phase transition much after inflation. In all of these scenarios, the resulting gravitational radiation can explain the tentative signals reported by the NANOGrav, Parkes, and European Pulsar Timing Array experiments if the reheating temperature of the hot big bang, and correspondingly the energy scale of the false vacuum, falls in the range ${T}_{*}\ensuremath{\sim}{\ensuremath{\rho}}_{\mathrm{vac}}^{1/4}=\mathrm{MeV}--100\text{ }\mathrm{GeV}$. All of the same models at higher reheating temperatures will be of interest to upcoming ground- and space-based interferometer searches for gravitational waves at larger frequency.

We apply the phenomenological model used to explain the abundances of Fe and r-process elements in very metal-poor stars in the Galaxy to [Fe/H] of damped Lyα systems. It is assumed that the first stars that formed after the big bang were very massive and that they promptly enriched the interstellar medium to [Fe/H] ~ -3, at which metallicity the formation of normal stars took over. Subsequent Fe enrichment was provided by Type II supernovae. The range of [Fe/H] at a given redshift z for damped Lyα systems is explained by the time t* after the big bang at which normal star formation started in an individual protogalactic system. The average t* is ≈80% the age of the universe for damped Lyα systems at z ≈ 1.5-4.5, indicating a long delay between the big bang and the turn-on of protogalaxies. It is inferred that a substantial fraction of the total baryonic matter may not have been aggregated into protogalaxies with normal star formation events until a late time corresponding to z ~ 1.5. The data near z = 2.2 indicate that the rate of turn-on of protogalaxies was initially very low and that it slowly reached a maximum at ~3 Gyr after the big bang. This rate of turn-on of galaxies may be important in understanding the rate of formation of quasars.