On the Transmutation of Atomic Nuclei by Impact of Material Particles. I. General theoretical Remarks. (all published)

Copenhagen, Levin & Munksgaard,1937. 8vo. Uncut in orig. printed wrappers. In: "Det KGL. Danske Videnskabernes Selskab. Mathematisk-fysiske Meddelelser. XIV,10". 40 pp. Fine and clean. First edition of the work in which Bohr introduced his famous Liquid Drop Model of the atom in order to interprete the nuclear structure. (The paper was not continued as Kalckar died the following year)."It had, of course, been clear to Bohr that analogies with atomic spectra could not be of help in interpreting his (earlier) picture of nuclear structure. Peripheral electrons, thinly spread within the atomic volume, can be compared to a dilute gas of particles interacting in pairs only. By contrast Bohr's picture of intranuclear motions of tightly bound nucleons should show 'essential collective aspects', he said. Now, together with Kalckar, he suggested that for nuclei a much more proper comparison would be with a drop of liquid. That analogy should not be taken too literally, the dynamics of a true liquid drop is vastly different from thta of nucleai. Yet the comparison, treated cautiously, was tempting and in the event proved fruitful in many respects, particularly in regard to collective motions."(Pais "Niels Bohr's Times", pp. 339-40)."In the liquid drop model, formulated by Niels Bohr, the nucleons are imagined to interact strongly with each other, like the molecules in a drop of liquid. A given nucleon collides frequently with other nucleons in the nuclear interior, its mean free path as it moves about being substantially less than the nuclear radius. This constant "jiggling around" reminds us of the thermal agitation of the molecules in a drop of liquid. The liquid drop model permits us to correlate many facts about nuclear masses and binding energies" it is useful in explaining nuclear fission. It also provides a useful model for understanding a large class of nuclear reactions." (FAQ).Rosenfeld No 56.…