Ugo Fano

2.1. Birth and family background

Ugo Fano was born on July 28, 1912, in Turin, Italy, into a wealthy Jewish family. His father, Gino Fano, was a distinguished professor of mathematics.

2.2. Education

Fano pursued his higher education at the University of Turin, where he earned his doctorate in mathematics in 1934. His doctoral thesis was titled Sul Calcolo dei Termini Spettrali e in Particolare dei Potenziali di Ionizzazione Nella Meccanica Quantistica, which translates to "On the Quantum Mechanical Calculation Spectral Terms and their Extension to Ionization". As part of his PhD examination, he also delivered two oral presentations: Sulle Funzioni di Due o Più Variabili Complesse ("On the functions of two or more complex variables") and Le Onde Elettromagnetiche di Maggi: Le Connessioni Asimmetriche Nella Geometria Non Riemanniana ("Maggi electromagnetic waves: asymmetric connections in non-Riemannian geometry"). The latter referred to Gian Antonio Maggi (1856-1937), an Italian mathematical physicist.

2.3. European years

Following his doctoral studies, Fano worked with Enrico Fermi in Rome, where he was a senior member of the renowned 'Via Panisperna boys' research group. During this period, at Fermi's urging, Fano developed his seminal theory of resonant configuration interaction, which led to the concept known as the Fano resonance profile. This foundational work was presented in two significant papers, published in 1935 and 1961. The 1961 paper, titled "Effects of Configuration Interaction on Intensities and Phase Shifts", is one of the most cited articles ever published in the Physical Review. From 1936 to 1937, Fano also spent time collaborating with Werner Heisenberg in Leipzig, further expanding his expertise in theoretical physics.

3.1. Immigration and early research

In 1939, Ugo Fano married Camilla Lattes, who was also known as Lilla. Camilla would later co-author an influential book on atomic and molecular physics with him. Later that year, Fano immigrated to the United States due to the escalating antisemitic measures being implemented in Italy, which severely restricted the rights and opportunities of Jewish citizens. This forced relocation highlighted the profound impact of societal discrimination on the lives of individuals.

Upon his arrival in the U.S., his initial research focused on bacteriophages and pioneering work in radiological physics. Specifically, he investigated the differences in the biological effects of X-rays and neutrons. During World War II, he served a period at the Aberdeen Proving Ground.

3.2. National Bureau of Standards (NBS) and University of Chicago

After his service during World War II, Fano joined the staff of the National Bureau of Standards (NBS), which is now known as the National Institute of Standards and Technology (NIST). He was notably hired as the first theoretical physicist on the NBS staff. He remained at the NBS until 1966.

In 1966, Fano transitioned to academia, joining the physics faculty at the University of Chicago. He continued his work there until the early 1990s, dedicating himself to training and mentoring approximately thirty graduate students and postdoctoral research associates. Many of his former students and associates have since achieved prominent positions in theoretical atomic physics and molecular physics across the United States, Europe, and Japan, a testament to Fano's lasting influence as an educator and mentor.

4.1. Key theories and concepts

Fano's most significant contributions to physics include several concepts and phenomena that bear his name, reflecting their foundational importance:

• Fano resonance profile: This describes a type of asymmetric resonance line shape that arises from the interference between a discrete state and a continuum of states. It is a fundamental concept in quantum mechanics and has applications in various fields, including atomic physics, condensed matter physics, and nanophotonics.
• Fano factor: This statistical quantity describes the deviation of the variance of a number of detected particles from the Poisson distribution, often used in the study of ionization and semiconductor detectors.
• Fano effect: A phenomenon related to the interaction of light with matter, particularly in the context of polarized light.
• Lu-Fano plot: A graphical method used in atomic spectroscopy to analyze the energy levels of atoms.
• Fano-Lichten mechanism: This mechanism describes inner-shell excitation in atomic collisions.
• Fano theorem: This theorem is crucial in radiation dosimetry, providing a principle for calculating the energy deposition in a medium exposed to radiation.

4.2. Fields of impact

Fano's work had a major and sustained impact across several primary fields of physics. He made fundamental contributions to:

• Atomic physics: His research significantly advanced the understanding of atomic structure and interactions, particularly concerning electron correlations and resonant phenomena.
• Molecular physics: Fano extended his theoretical frameworks to molecular systems, contributing to the understanding of molecular spectroscopy and collision processes.
• Radiological physics: His early work on the biological effects of X-rays and neutrons, and his development of the Fano theorem, were critical for the field of radiation dosimetry and protection.

Most areas of current research in these subjects continue to reflect his fundamental contributions, underscoring the enduring relevance of his work.

4.3. Publications and writings

Ugo Fano was a prolific author, and his publications significantly shaped the understanding of atomic and molecular physics. Among his most influential works is the book Physics of Atoms and Molecules, published in 1959, which he co-authored with his wife, Camilla Lattes. Appendix III of this book provided an elementary description of the collision of two charged particles, a concept famously utilized by Richard Feynman in lectures that were later published as Feynman's Lost Lecture: Motion of Planets Around the Sun. An expanded version of this foundational text was subsequently published in 1972 under the title Basic Physics of Atoms and Molecules.