The infrared optical properties of silicon reported by different workers disagree by far more than the precision of the measurements. Further, their extrapolations conflict with THz measurements. These inconsistencies are commonly attributed to crystal defects or impurities, but lack of reliable intrinsic silicon values hampers separation of host and defect effects. We have developed tests based on linear-response theory to address this. Tests include requiring that the refractive index is an even function of photon energy, and comparing the coefficients of a Taylor expansion of the IR index with the moments of the electronic absorption above the band gap. The latter is sufficiently well known for silicon that predictions for the intercept, slope, and curvature, of the index may be used to test infrared measurements for consistency. Thus, we identified the sources of conflict as: (i) A physically inconsistent assumption for index parity commonly made in analysis of channel-spectra. (ii) Defect and free-carrier absorption. Eliminating data sets with these shortcomings resolved the conflict between measurements and allowed us to develop a composite set of IR optical constants for silicon that is a best fit to reliable measurements from microwaves to the visible.

Ugo Fano was a lively, challenging and creative physicist, known for his wide-ranging studies in atomic physics, radiological physics and radiation biology, and statistical physics and relaxation. He stimulated and guided a cadre of students, postdoctoral associates, and colleagues whose admiration and affection for him continued, as did their interactions with him, throughout his life.

The symposium succeeded in bringing forth valuable surveys of current topic ranging from fundamental physics and chemistry related to the interactions of charged particles or photons with matter, to advanced instrumentation including accelerators and analyzing systems, and to applications to materials science, biology, and medicine. The present article summarizes salient points of most of the lectures of the symposium. Incisive outlook and germs of ideas for work in the near future were apparent in some of the lectures.

Radiation ionizing radiation dosimetry radiation detectors radiation-matter interactions physics entails studies of the interactions of ionizing radiation with matter. The term ionizing radiation refers to any energetic particles, either charged or uncharged, that can ionize atoms or molecules in matter. These particles include photons in the ultraviolet, X-ray, or γ-ray spectral region; electrons and positrons; mesons; protons and deuterons; α-particles; heavier ions including molecular ions; and neutrons. The matter under consideration includes substances in every phase of atomic aggregation (i.e., gas, liquid, solid, or plasma). Strictly speaking, the term "ionization" signifies an event in which at least one electron leaves an atom or molecule and eventually becomes free. This notion applies to a dilute gas, but not to condensed matter, for which it would be more precise to use the term "electronic activation" encompassing all modes of excitation, as sketched in Sect. 92.3.5.

The mean excitation energy for the stopping power of matter, usually expressed by symbol I, is the only nontrivial material property in Bethe’s [Ann. Phys. 5, 325 (1930)] asymptotic stopping-power formula. It is therefore a crucial input for the evaluation of stopping power for swift charged particles. To calculate the I value of a material from its definition, it is necessary to know the oscillator-strength spectrum of the material in question over the entire range of the excitation energy. We evaluate the mean excitation energies of 32 atoms and molecules from the oscillator-strength spectra that were published by Berkowitz in 2002 [Atomic and Molecular Photoabsorption: Absolute Total Cross Sections (Academic, San Diego, 2002)]. We find that most of the present I values are consistent with those given in the literature. The I values of NO2, O3, and C60 in particular are evaluated in the present work. For buckminsterfullerene C60, an estimation of the I value is made also using the local-plasma approximation, in an attempt at understanding differences in the I values of carbon in a free atom, a C60 molecule, and graphite. Systematic trends of I values obtained in the present calculation are discussed, in the context of the Thomas-Fermi model.

We discuss the contributions of Hans A Bethe to the fields of atomic, molecular and optical physics. Those contributions are seminal to these still vibrant major areas.

We have evaluated the mean excitation energy or I value for Coulomb excitations by swift charged particles passing through carbon, aluminum and silicon. A self-consistent Kramers–Kronig analysis was used to treat X-ray optical spectra now available from synchrotron light sources allowing us to carry out Bethe’s original program of evaluating I from the observed dielectric response. We find that the K and L shell are the dominant contributors to I in these light elements and that the contribution of valence electrons is relatively small, primarily because of their low binding energy. The optical data indicate that Si and Al have nearly equal I values, in contrast to Bloch’s Thomas–Fermi result, I∝Z. The optically based I values for C and Al are in excellent agreement with experiment. However, the dielectric-response I value for Si is 164±2eV, at variance with the commonly quoted value of 173±3eV derived from stopping-power measurements.

Known as the father of electron and proton Monte Carlo methods, Martin Jacob Berger, chief of the radiation theory section of the National Bureau of Standards (now NIST) for more than 20 years, died in Bethesda, Maryland, on 6 November 2004 from the effects of a hematoma after a fall in which he struck his head.Born in Vienna in 1922, Martin left Austria in 1938 just before its annexation by Nazi Germany. After 18 months in England, he immigrated to the US in 1940 and earned a BS in physics from the University of Chicago three years later. He became a US citizen in 1944, joined the Army, and served in the Aleutian Islands until 1946. Shortly after his discharge, he began his graduate work at the University of Chicago and earned an MS (1948) and a PhD (1951), both in physics. He prepared his doctoral thesis under Marcel Schein on “Multiple Scattering of Fast Protons in Photographic Emulsions” and stayed on for a one-year postdoctoral fellow-ship in mathematical statistics.Martin had heard that Ugo Fano and Lew Spencer of NBS had been doing work on ionizing radiation, so he wrote to them, was invited for an interview, and was hired. In September 1952 he joined the radiation theory section, headed by Fano, within the atomic and radiation physics division, led by Lauriston Taylor. Twelve years later Martin became chief of the radiation theory section and was in charge of as many as 12 physicists; he held that position—through various reorganizations and a renaming—until his retirement in 1988.At NBS in the 1950s, Martin concentrated first on the transport of gamma rays and the development of photon Monte Carlo methods. He pioneered Monte Carlo calculations in complex media and extended them to realistic configurations involving boundaries and inhomogeneities. For the work on photon transport, Martin collaborated with colleagues in the radiation theory section to survey and compile cross-section information. One such colleague was Rosemary McGinnies, who wrote several important early evaluations. In 1960 Martin married Rosemary; they later had three children and six grandchildren. Over the years, Martin retained his interest in photon-interaction cross sections and collaborated on critically evaluated databases that have become a standard for radiation-transport calculations.Martin shifted his focus to charged-particle transport, with an emphasis on electrons and protons. His 1963 article “Monte Carlo Calculation of the Penetration and Diffusion of Fast Charged Particles,” which appeared in Methods in Computational Physics, thoroughly delineated the taxonomy, methods, underlying single- and multiple-scattering distributions, and algorithms used in charged-particle Monte Carlo codes. That work was a departure from the few earlier papers done by other authors mostly for calculations of showers in high-energy approximations. In his study, Martin developed a comprehensive approach in which he used the most accurate distributions available to describe the transport of radiation at energies of interest in medical and radiation-protection physics.With his 1963 paper, Martin literally established the modern Monte Carlo calculation of charged-particle transport. The methods he developed and the cross-section data for which he was largely responsible are imbedded in nearly all of today’s coupled photon–charged-particle Monte Carlo codes. The use of electron–photon Monte Carlo calculations are now widespread, and the field has matured so much that scientists in many disciplines now rely heavily on the results of the better-known Monte Carlo codes rather than much more difficult measurements. Perhaps the most telling compliment is that his early pioneering work is still remarkably relevant today, more than 40 years later.Martin was also responsible for an extensive body of critically evaluated radiation-interaction data. These data were not only necessary for his transport calculations but have become standard reference data for the radiological sciences. They include stopping powers and ranges for electrons, positrons, and heavy charged particles, and cross sections for the bremsstrahlung production by electrons and for the elastic scattering of electrons and positrons. During his Monte Carlo development work, Martin was also busily applying his methods to important problems in radiological physics. He calculated detector-response functions for radiation spectroscopy; performed microdosimetric calculations; and conducted numerous studies of the absorbed dose and the penetration of photons, electrons, bremsstrahlung, and protons in materials of interest in dosimetry, radiation protection, radiation shielding, auroral physics, and radioactivity standardization. After his retirement, he continued that work as a consultant for NBS and other agencies.Martin’s work was scientifically impeccable. He attacked each problem in his own way, which usually became the standard way. He frequently selected problems that others had not worked on and gave correct, straightforward, and useful solutions. In recognition of his enduring contributions, the International Commission on Radiation Units and Measurements awarded Martin its L. H. Gray Medal in 2003.The radiological community has lost an important scientist. Martin Jacob Berger PPT|High resolution© 2005 American Institute of Physics.

physica status solidi (c)Volume 2, Issue 1 p. 310-313 Original Paper Ultraviolet color centers and refraction in silicate glasses D. Y. Smith, Corresponding Author D. Y. Smith dysmith@uvm.edu Department of Physics, University of Vermont, 82 University Place, Burlington, VT 05405, USA Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USAPhone: +1 802 656-0058, Fax: +1 802 656-0817.Search for more papers by this authorE. Shiles, E. Shiles Department of Physics, University of Vermont, 82 University Place, Burlington, VT 05405, USA Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USASearch for more papers by this authorMitio Inokuti, Mitio Inokuti Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USASearch for more papers by this author D. Y. Smith, Corresponding Author D. Y. Smith dysmith@uvm.edu Department of Physics, University of Vermont, 82 University Place, Burlington, VT 05405, USA Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USAPhone: +1 802 656-0058, Fax: +1 802 656-0817.Search for more papers by this authorE. Shiles, E. Shiles Department of Physics, University of Vermont, 82 University Place, Burlington, VT 05405, USA Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USASearch for more papers by this authorMitio Inokuti, Mitio Inokuti Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USASearch for more papers by this author First published: 19 January 2005 https://doi.org/10.1002/pssc.200460172Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract We studied the uv absorption of optical glasses to clarify the role of disorder and modifier ions in deter-mining the refractive index for visible light. We find these uv absorptions are analogous to traditional color-center spectra. Processes include ionic absorption and perturbation of host excitons. These absorptions essentially determine the visible index, which is predicted to within a few percent from the uv spectrum by the generalized Cauchy dispersion formula [Rad. Eff. Defects Solids 157, 823 (2002)]. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Citing Literature Volume2, Issue1January 2005Pages 310-313 RelatedInformation

The reflectivity spectra of representative glasses were analyzed to obtain their uv absorption spectra. From these, we show that the first few inverse moments of the absorption give a good representation of the refractive index for visible light when used with the generalized Cauchy dispersion formula [Radiat. Eff. Def. Sol. 157 (2002) 823]. The absorption spectra also illustrate the roles of modifier ions in determining the visible refractive index. These include introduction of ion-specific absorptions (uv color centers); broadening, shifting and altering the strength of glass-former absorptions; and alteration of the density and structure of the glass' random network.

With the passing of Ugo Fano on 13 February 2001, Comments on Atomic and Molecular Physics lost a longtime correspondent since its founding in 1969. A broader community dearly misses a great theoretical physicist.