Positive Excess in Mesotron Spectrum

Abstract

Fast (Rn+Be) <r =0.9 X10"" cm 2 a =0.6 X10 -27 cm 2 Thermal (Cd group) o-=1.2 X10" 27 cm 2 <r =0.9 X10~2 7 cm 2We believe that the mass number to be attributed to Br (1) is 84. Indeed, according to our experiments it is unlikely that Br (1) and Br (2) are isomers. On the other hand, Snell 4 has found in the bromine fraction separated from rubidium irradiated by fast neutrons (Li + D) two periods of 35 min. and 34 hr. The second period has to be attributed to Br 82 , resulting from the reaction Rb 85 (n, a) Br 82 . The fact that the first of the Snell periods agrees with the period of Br (1) suggests that we have to do with the same body, probably Br 84 which could result, in Snell's experiments, from the reaction Rb 87 (n, a) Br 84 .We have determined the cross sections for the production of Br (1) and Br (2) by thermal neutrons (cadmium group) and fast (Rn+Be) neutrons. All of the factors entering into this evaluation (yield of the chemical methods, absorption of the radiation, etc.) have been determined experimentally.These results show that the radioactive bromine isotopes are produced in a very small proportion (at most 1 percent) during uranium fission due to neutrons. i A.

On the Disintegration of Slow Mesons

“…Moreover, if one assumes that one-half of the hard component is formed by stable particles having the same sign, one would expect a variation of the positive excess with the total number, while direct experiments showed that such an excess keeps constant between 3500 m above the sea level and the sea level. 14 In conclusion it seems that Tomonaga and…”

The Italian contributions to cosmic-ray physics from Bruno Rossi to the G-Stack. A new window into the inexhaustible wealth of nature

“…Cloud chambers experiments had then shown an approximately equal number of positive and negative particles [82], but Louis Leprince-Ringuet in 1937 [83], Haydn Jones in 1939 [84], and Donald J. Hughes in 1940 [85] had found a positive excess of about 20 percent. Bernardini then proposed to "repeat the experiment of Rossi with a somewhat improved triple coincidence arrangement" (see [86], p. 536; see also [87,88]; figs. 10a-10b-10c).…”

“…. ] under conditions when the elaborate Wilson chamber technique is impossible" (see [86], p. 536). They performed more experiments in the years 1941-1943 and published several papers (see in particular [87,86,88,89]).…”

“…under conditions when the elaborate Wilson chamber technique is impossible" (see [86], p. 536). They performed more experiments in the years 1941-1943 and published several papers (see in particular [87,86,88,89]). In an outline of their research work, published in the Physical Review in 1945 [90], they explained that they had investigated the energy spectrum and positive excess of the hard component of cosmic rays for "cogent reasons", as "the positive excess in the meson spectrum is probably connected with the positive nature of the primary radiation" and "a study of the variation of the positive excess with height would probably be interesting and might throw some light on the process of creation of the mesons" (see [90], p. 110).…”