Nuclear resonance excitation using a diffraction monochromator

Abstract

Nuclear resonance scattering from the first excited states in F19 and Mn55 has been studied with the bent-diffraction-crystal monochromator. The experiment was performed by observing the scattered radiation from nuclei exposed to nearly monoenergetic x rays selected by crystal diffraction from the bremsstrahlung spectrum of an x-ray tube. Gamma rays scattered at 135° from samples of lithium fluoride and manganese placed in the diffracted beam were observed as a function of the incident photon wavelength. With the lithium fluoride sample three measurements were made under different experimental conditions. In each case pronounced resonance peaks 10 to 15% above background were observed. A least-squares analysis of the data gives 109.894±0.005 keV for the energy position of the first excited level in F19. From the observed yield the width of this level was deduced to be (5.1±0.7)×10^-7 eV. Measurements with a Mn55 scattering sample gave 125.95±0.01 keV for the position of the first excited level and (1.1±0.3)×10^-6 eV for the resonance width.