Effect of the Electric Quadrupole Interaction on theγ−γDirectional Correlation inCd111. III

Abstract

1287 one arrives at an upper limit for the width of the 665-kev excited state of Mo 97 , r<5XlO~4 ev, and at a lower limit for the lifetime of this state of 1.5X10~1 2 second. This lifetime is one order of magnitude longer than the one expected from the Weisskopf formula. Thus, the Ml transition in Mo 97 shows the same behavior as the low-energy MVs.It should be mentioned that the Mo 97 transition, as well as most of the low-energy transitions measured by the Canadian group, involve a change of two units of orbital angular momentum, whereas the Li 7 gamma ray presumably leads from a p\ to a p\ state.t Assisted by the joint program of the U. S. Fig. 1 is one of two obtained in a hydrogen-filled diffusion cloud chamber exposed to a beam of 1.5-Bev negative pions 0~) from the Cosmotron. The hydrogen was at a pressure of 18 atmospheres, and a field of 11 000 gauss was applied. The picture is believed to represent the production of a Vi° particle by a TT~ interaction with a proton. Track a is the incident w~, the end point of which is to be called A. Tracks b and c are the decay products of the Vi°. A single neutral heavy meson also may have been produced at A, which would travel in the direction indicated by d. 1 Since track a is short, its momentum can only be estimated to lie near the nominal TT" beam momentum of 1.63 Bev/c. This track is parallel to the other beam tracks and thus probably is not due to a secondary particle. The line connecting point A with the vertex of b and c, to be called G, forms an angle of 26° with a. The distance between A and G is 0.65 cm. Tracks a, b, and c are coplanar, while only coplanarity of A, b } and c is necessary for the tracks to be associated. In addition, the components of momentum of b and c perpendicular to line AG balance. Track b forms an angle of 16° with a; b is caused by a positive particle with a measured momentum of 480±80 Mev/c and an estimated ionization density of 3X minimum. Thus b is identified as a proton track. The angle between b and c is 37°. Track c is negative, with a momentum of 210±70 Mev/c and estimated ionization density of less than 1.5X minimum. An upper limit of 410 m e is inferred for its mass, indicating a IT. Assuming that b and c represent the decay of a Fi°(->/>-Hr~+()), one finds a Q-value of 51 Mev from these data. 2 Assuming the generally accepted Q of 37 Mev one would find that, for the given angles, the momenta should be 460 Mev/c for the proton and 180 Mev/c for the iT. These values fall within the errors given for the measured values and have been used for the further computations. The lifetime of this Fi° is 4X10" 11 sec. T HE photograph reproduced inThe total energy of the Fi° is 1.26 Bev, and its momentum is 610 Mev/c. To conserve energy and momentum at least one other neutral particle must start at A. Assuming a single particle, its total energy would have to be 1.31 Bev and its momentum 1.11 Bev/c, leading to a mass of 1350±70 m e for a kinetic energy of 1.5 Bev for the incident it~. For an energy of 1.2 Bev instead of 1.5 Bev one wo...

Sur les corrélations angulaires des électrons de conversion, avec une étude particulière de la cascade du 111Cd

“…D'autre part, on peut, la perturbation apportée par le champ électrique étant connue, par exemple dans un monocristal, calculer le couplage quadrupolaire. Une évaluation grossière du gradient de champs dans le monocristal d'indium métallique utilisé donne pour le moment quadrupolaire du premier état excité rv I O-'24 cm2 [4], [5]. 4.…”

“…Une évaluation grossière du gradient de champs dans le monocristal d'indium métallique utilisé donne pour le moment quadrupolaire du premier état excité rv I O-'24 cm2 [4], [5]. 4. En général, on obtient la corrélation angulaire non perturbée avec des sources fluides, par exemple des solutions aqueuses.…”

Influence des électrons périphériques de l'atome sur la corrélation angulaire de rayonnements nucléaires successifs

“…Les mesures des rayonnements y donnent des renseignements sur l'ordre de multipolarité; celles des rayons 0 renseignent sur le degré d'interdiction et sur les éléments de matrice participant à la transition. Des expériences récentes [4], [7], [8] [22]. Si, d'autre part, la distribution des charges des électrons n'a pas la symétrie sphérique, on obtient un terme additionnel électrique : Ici Q est le moment quadrupolaire du noyau.…”

“…Dans un travail paru l'année dernière, de Abragam et Pound [3], on examine l'expérience de découplage sur des atomes non libres. Les auteurs montrent que, si le cortège électronique est couplé avec le champ du cristal, on ne peut pas obtenir un découplage appréciable avec un champ satisfaisant à la condition (7). Il semble aujourd'hui que l'on puisse expliquer tous les effets observés sur 111Cd avec la seule interaction quadrupolaire; je développerai ce point de vue dans le paragraphe suivant.…”

“…Pour expliquer les résultats sur 111Cd, l'hypothèse de l'interaction quadrupolaire électrique est plus fructueuse que celle de l'interaction dipolaire magnétique. Les expériences avec un monocristal[7] le montrent de la manière la plus convaincante. Les atomes actifs ont été introduits dans un monocristal tétragonal d'indium.…”