STUDIES ON THE RANGE OF 140Ba IN PROTON-INDUCED FISSION OF 238U AND A SEMI-EMPIRICAL DERIVATION OF A GENERAL RANGE–ENERGY RELATION

Abstract

Ranges of ¹⁴⁰Ba have been measured in the forward and backward directions with respect to the proton beam by bombarding uranium foils of normal isotopic composition with protons of 15, 30, and 60 MeV energies. Successive thin layers of aluminium were removed from the front and back catchers by an electrochemical technique, and the ranges were calculated from the relative distribution of ¹⁴⁰Ba activity in the different layers. The calculations indicate that full momentum transfer of the incident protons has taken place, suggesting that the compound nucleus mechanism is predominant at these energies.An analysis of the existing range and energy data for fission fragments has shown that the 'effective charge' of a fission fragment, first postulated by Bohr, can be expressed as a function of the charge and the mass of the medium being penetrated. The original range–velocity relation of Bohr has been modified to include the above fact and has led to a general range–velocity relation for ranges in different metallic catchers. Similar equations seem to be applicable to the range data in gaseous media.