The Hydrogen Atom III: Precision Physics of Simple Atomic Systems (PSAS 2004), is an international conference devoted to physics of simple atoms and related problems. A sequence of conferences - Hydrogen I (Pisa, Italy 1991), Hydrogen II: Precision Physics of Simple Atomic Systems (Castiglione della Pescaia, Italy, 2000), PSAS 2002 - Precision Physics of Simple Atomic Systems (St.Petersburg-Pushkin, Russia, 2002) - have been devoted to fundamental physics with simple atomic systems.

Physics of simple atoms offers a good chance for interdisciplinary exchanges between atomic physics, laser spectroscopy, quantum field theory, nuclear and particle physics. The conference program also contains several topics related to specific problems associated with fundamental constants, high-precision experiments and metrology. Our meeting follows The Hydrogen Atom II which took place in Castiglione della Pescaia, June 1-3, 2000. As it has been understood there it would be fruitful to organize Hydrogen atom meetings one per four years, while a smaller meeting could take place in between. Recent PSAS 2002 conference in St. Petersburg (2002) showed essential progress in field since 2000 and needs for the coming Hydrogen Atom III meeting.

In 2004 the Hydrogen Atom conference will be held on the period of 01-04/August in Hotel Porto Real Resort in Mangaratiba in the paradise region of Angra dos Reis, two hours south of the city of Rio de Janeiro. The estimated number of participants of Hydrogen Atom III is 100.

As the two previous Hydrogen Atom conferences ours will be a satellite meeting of the International Conference on Atomic Physics (ICAP'2004). We are planning to have a kind of joint sessions with ICAP, at the end of it. The ICAP'2004 is to be held in hotel Gloria in Rio de Janeiro, from 25-30/July/2004.

The Hydrogen atom III meeting will be devoted to simple atomic systems. Such atoms provide an opportunity doing atomic physics to learn something beyond it, such as fundamental interactions, fundamental constants, fundamental symmetries, properties of simple nuclei and particles.

The main objectives of the Hydrogen atom III are fundamental tests of Physics with these simple and sometimes quite exotic atomic systems with an interplay between theory and high precision measurements. The main topics of interest for the edition are, among other wellcomed suggestions, among other wellcomed suggestions:

• High resolution spectroscopy of hydrogen and helium
• Precision study of muonium and positronium
• Spectrum of few-electron medium- and high-Z ions
• Study of muonic and exotic atoms
• Precision measurements and frequency metrology
• Fundamental constants
• Production and spectroscopy of antihydrogen
• Search for new physics via atomic spectroscopy
• Structure of proton and light nuclei
• Bound state quantum electrodynamics
• Advanced quantum mechanics of Coulomb bound systems

Detail of the previous meetings can be found in their web sites (Hydrogen II and PSAS 2002) and in their proceedings:

• PSAS 2002 contributed papers have been published in Canadian Journal of Physics 80-11(2002) while the invited reviews have formed a book published by Springer-Verlag later this year as Lectures Notes in Physics.
• Hydrogen II materials were published by Springer-Verlag in Lectures Notes in Physics. The Table of Contents contains information on a book of review papers and an attached CD with contributed papers.
• The same edition contains a scanned copy of proceedings the Hydrogen Atom I meeting which were originally published by Springer-Verlag in 1989.

In addition to the above First Registration, please notice the following items: