Baldwin's fields of research included photo-nuclear reactions with bremsstrahlung radiation from electron accelerators, resulting in the discovery of the giant dipole resonance; orbit dynamics of synchrotrons; nuclear reactor physics; electrical propulsion for space; low-energy electron scattering in gases; nonlinear optics; and investigation of the feasibility of a gamma-ray laser. His early research involved perfecting GE's 100 MeV Betatron for use as an x-ray source. Using bremsstrahlung radiation from the betatron beam, he and G. S. Klaiber excited uranium nuclei and observed a prominent peak at about 20 MeV in the cross section for photons,, which was not anticipated by the nuclear physics community. This "giant dipole resonance" discovered by Baldwin and Klaiber was subsequently explained theoretically by Edward Teller and Maurice Goldhaber, and others. Baldwin's research with low-energy electron scattering on noble gases extended the scattering cross-section data to very low energies, well under 1 eV, a technically difficult task. His book "An Introduction to Nonlinear Optics" helped bridge the gap in knowledge between specialists in the field and engineers and technical managers involved with this new technology. Baldwin, along with GE colleagues, developed ideas for nuclear radiation analogues of the optical laser, now known as the gamma-ray laser, or Gamma-Ray Amplification by Stimulated Emission of Radiation. He launched international efforts to define and quantify issues facing the development of this advanced idea, working with many academic colleagues, including R. V. Khokhlov and V. I. Gol'danskii of the USSR and J. C. Solem of Los Alamos, opening an entirely new field of physics and making bold, creative attempts to bring the concept to fruition,,. He authored an early bibliography of literature on the problem of developing gamma-ray lasers, covering the period 1917 through 1979. Baldwin investigated methods for detecting nuclear stimulated emission, seeking to demonstrate coherent emission from nuclear states, but establishing that a number of innovative ideas were unworkable. He and his colleagues identified criteria necessary for the process of laser action at gamma-ray energies. He collaborated on theoretical issues, on experiments to demonstrate isomer separation by selective photoionization, and on modeling of the kinetics of gamma-ray lasers. Decades of his gamma-ray laser work, together with that of others, is assessed in a paper and a second assessment concentrates on later work on recoilless gamma-ray lasers. These review papers contain an extensive list of references. He collaborated with J. C. Solem on research on the use of x-ray microholography to image biological specimens.
Personal life
Baldwin's 57-year marriage to his wife Winifred, who collaborated as copy editor and typist for many of his publications, produced three children and seven grandchildren, of these three obtained a college degree in physics. Baldwin was an avid amateur astronomer, grinding his own lenses and building his own telescopes; fisherman; self-taught pianist, entertaining friends by playing by ear; and historical researcher. One of Baldwin's notable accomplishments was locating an inscription left by the Dominguez-Escalante expedition of 1776, discovered originally in 1884 by his father on a surveying expedition in northern Arizona. Baldwin organized the 1995/1996 Museum of New Mexico expeditions that found the Escalante inscription and documented this in the Journal of the Southwest.
