ACKNOE1LEDGEMENTS INTRODUCTION CHAPrlR I -The Extracted Beam of the McGill Cyclotron 63 69 72 74 84 i ABSTRACT The extracted bearn of the cyclotron was modified to -10 give a higher intensity of 1.31 x 10 amps. It had an energy of 90.6 Mev with a full width at half maximum of 1.2 Mev. This was used to investigate Bi 209 (p, xn) Po 2 l(}-xn reactions which produced short-lived isomerie states in Po. Two new isomers were discovered in Po 2 CJ7 and a new 0 -ray was discovered in the decay of a

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... iously known isomer in Po 205 • A search in the energy range from 90-10 Mev, and in the time range from lo-5 sec to 10-l sec was made with no other decays observed. The two isomers in Po 207 were found to have respectively t-rays of 260 Kev(E3) with a half-life of 2.5 sec and 310 Kev (M2) wi th a half-life of 47 )"-Sec, the latter being followed by an 820 Kev (E2) t-ray. The 644 }'Sec isomer in Po 20 5 was examined and found to have a new ~-ray at 160 Kev. · Ana.lysis of the system led to the assignment of this decay scheme as 160 Kev (M2) followed by a 707 Kev (E2). These decays were compared with the level systematics in lead and the two short half-lives assigned as being from the i 13/2 state in polonium. ii ACKNGJLE.'DGE!-'IENTS The author wishes to express his great appreciation to Dr. W.M. Martin for numerous helpful suggestions and his encouragement in the completion of this work. Thanks are due to Dr. J.S. Foster for his support and for making available the laboratory with its ample facilities. Ivfu.ch a ppreciation is felt for the many helpful suggestions of Dr. R.E. Bell. Mr. S. Doig and his staff in the machine shop were most helpful in the construction of equipment and with suggestions in design, as was ~oe. K. Heinstein in the construction of the electronics. Many thanks are due b·. R.H. Mills for the operation of the cyclotron and discussions relative to it. 5. Ha1f-lives between 2 x 10-5 sec and 10 sec. With these changes two new isomers have been discovered 207 205 in Po and additiona1 information has been obtained on Po previous1y studied by Link(l4). In brief, the two new isomers found were Po 207 m1 and Po 207 m2. Po 207 m1 has a ha1f-life of 47 :!:. 3 jAsee. It is deexcited by emission of two y-rays, one 315 Kev (M2), the other 820 Kev (E2). Po 207 m2 has a ha1f-1ife of 2.5 ! 1 sec. It deexcites by emission of one 260 Kev (E3) y-ray to the isooeric state of Po 2 07m1. The previous1y found isomer in Po205m was reexamined and a new d-ray was found of 160 Kev. It was assigned as an M2 and the other ;r-ray of 707 Kev was assigned as E2. -4-CH.API'ER I THE EXTRACTED BEAH OF THE MC GILL CYCLCYrRON 1 1 J 1-' 1-' ' 1 .