Ronald A. Phaneuf

Research Interests

Research in this program focuses on quantitative experimental investigations of processes that occur in high-temperature plasma environments. Most of the known matter in the universe exists in the ionized plasma state, and most of the information we have about the distant universe comes to us in the form of light or energetic particles produced by atomic interactions. Examples are the solar corona and stellar atmospheres. Hot plasma environments with similar conditions may also be created on earth, for example in pulsed-power and laser-produced plasmas and in fusion reactors. Current experiments probe the interactions of photons and electrons with atomic, molecular and cluster ions. Experiments are designed to probe the nature of fundamental interactions, but also to provide quantitative data for testing theoretical collision models and for diagnostics of high-temperature plasmas.

The research in this program has two main emphases, one based on the UNR campus and the other in Berkeley, California at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory.

A multicharged ion research facility based on a 14.4-GHz CAPRICE electron-cyclotron-resonance (ECR) multicharged ion source is capable of delivering intense, continuous beams of ions in charge states as high as +30. Experiments probe charge-changing collision processes such as electron capture and impact ionization using gas-target and interacting-beams techniques. The signatures of these collison events are investigated by ion charge-state analysis, by Auger electron or by photon spectroscopy. A dynamic-crossed-beams apparatus is used for absolute cross-section measurements for the electron- impact ionization process. Such collisions are in many cases dominated by the excitation of inner-shell electrons. The next stage of development of this experiment will involve measurement for the first time of the energy distribution of electrons ejected in the ionization process. This new technique is expected to provide important new insights into complex ionization mechanisms.

A photon-ion research facility developed at UNR is permanently installed at the ALS in Berkeley, one of the world's brightest source of low-energy X-rays and extreme ultraviolet light. Research at this facility concentrates on high-resolution absolute measurements of photoionization of atomic, molecular and cluster ions in the 17-340 eV photon energy range. Such measurements with ions uncover a rich tapestry of resonances associated with the excitation of inner-shell electrons and multiply excited states that decay by autoionization, revealing details of their electronic structure and dynamics. An ECR ion source facilitates measurements with multiply charged ions and systematic studies along ionic sequences. UNR is the lead institution in an international collaboration that has engaged scientists from the United States, Mexico, Germany, Brazil, Great Britain, Denmark and Hungary.

In addition to the physics of fundamental processes, students in this program have an opportunity to learn many practical techniques that are widely employed in the scientific and technical workplace. These include ultra-high vacuum, charged-particle optics, electron, ion and photon spectroscopy, fast-timing, coincidence and position-sensitive detection of single particles, microwaves, high-voltage, computer data acquisition and control, and computer-aided design.

Former M.S. and Ph.D. graduates of this program are employed by the semiconductor industry, by academic institutions and by national laboratories.

This research program is supported by the Division of Chemical Sciences, Geosciences and Biosciences of the United States Department of Energy

The Research Team

Current Students

Mustapha Habibi (Ph.D.) [4d photoexcitation of free Ce ions and of Ce ions in a fullerene cage]

David Esteves (M.S.) [photoionization of ions for determination of astrophysical elemental abundances]

Kiran Baral (Ph.D.) [photoionization and electron-impact ionization of ions]

Nagendra Aryal (Ph.D.) [photoionization and electron-impact ionization of ions]

Alex Carr (B.S.) [production of fullerene anions by impact of C₆₀ ions on a metal surface]

Recent Graduates

Ghassan Alna'Washi (Ph.D., 2007) [Photoionization of Chlorine-like K²⁺ and Ca³⁺]

JingCheng Wang (M.S., 2006) [Photoionization and Electron-impact Ionization of Ar⁵⁺]

Miao Lu (Ph.D., 2006) [Photoionization and Electron-Impact Ionization of Multiply Charged Krypton Ions]

Mohammad Gharaibeh (Ph.D., 2005) [Systematic Photoionization Study along the Iron Isonuclear Sequence]

Erik Emmons (M.S., 2004) [A Complementary Study of Photoionization and Electron-Impact Ionization of an Atomic Ion: Xe³⁺]

Alejandro Aguilar (Ph.D., 2003) [Photoionization of Positive Ions: The Nitrogen Isoelectronic Sequence]

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