Frank Firk

Frank Firk's picture
Prof Emeritus Physics
SPL 34
Research Areas: 
Experimental Nuclear Physics
Biographical Sketch: 
Professor Firk carried out research in Nuclear Physics for more than sixty years. His main interests were in the fields of very high-resolution neutron spectroscopy at energies from a few electron volts to several hundred million electron volts, photonuclear reactions, neutron polarization, and nuclear instrumentation. From 1952 until 1965 he was a member of the Nuclear Physics Division at the Atomic Energy Research Establishment, Harwell, UK, and from 1965 until 1999 he was a member of the Department of Physics at Yale University. His studies with J. E. Lynn and M. C. Moxon (1953-1960) of the spacing distribution and reduced neutron width distribution of neutron resonances in heavy nuclei were of critical importance in establishing both the Wigner spacing distribution of the resonances (the basis of the wide-ranging field of Random Matrix Theory) and the Porter-Thomas distribution of the reduced neutron widths. A study of the interaction of neutrons with vanadium-51, carried out with J. E. Lynn and M. C. Moxon in the period 1958-1963, showed for the first time that the nuclear radius is spin-dependent. J. H. Gibbons and he (work carried out at the Oak Ridge National Laboratory, TN, 1960-1961) obtained clear evidence of direct (non-resonant) radiative capture of neutrons in medium-mass nuclei. High-resolution measurements (carried out with K. H. Lokan, 1961-1963) provided the first evidence of fine structure in the energy spectra of photoneutrons throughout the region of the giant electric dipole resonance in light nuclei. His earliest work at Yale involved the discovery of anomalous isospin mixing in the dipole states of oxygen-16 and carbon-12. With his student Ravinder Nath he developed the generalized neutron spin-precession method for studies of polarization effects in neutron physics. The method was an essential part of the first measurement of true double-scattering of neutrons by carbon-12. This work was carried out with his student R. J. Holt. In 1970, he obtained the first direct evidence of isospin splitting of the giant dipole resonance in any nucleus. In 1981, he and his graduate student Masuma Ahmed set a new upper limit on the value of the electric polarizability of the neutron. His measurements of the polarization of photoneutrons emitted from the giant dipole states in oxygen-16 (1991, 1995) remain the standard to this day. He contributed to the design, development, and use of high current electron linear accelerators for use in Nuclear Physics, beginning in 1952. He originated the use of very short (nanosecond), high-current electron pulses using the "stored energy mode" in traveling-wave accelerators. In 1956-57, he and the late Dr. Ernest Rae carried out the first experiment to measure two parameters, simultaneously, using magnetic tape recording involving 100 x 100 channels of information. This work is the forerunner of the multichannel, digital systems that are in such wide use today. He made key contributions in the area of scintillation detectors, particularly in the pioneering work with Ginther and Slaughter (1960-1961) in which they developed and used the first 6Li-loaded glass scintillator for neutron detection. For more than fifty years, this scintillator has remained the detector of choice for many neutron studies at energies up to about 100 keV. After 1993, his main interests were concerned with the mathematics of statistical distributions not only of the spacing distribution of neutron resonances but also of number-theoretic systems involving prime numbers and the zeros of the Riemann zeta function. He published more than 100 research papers, and since his 85th birthday, he has published 10 books.
Ph.D., London, 1967