$α$ -decay branching ratios for ${}^{151}{Tb}$ , ${}^{150 - 153}{Dy}$ , and ${}^{152 - 155}{Er}$

The isotopes

{}^{152 - 155}{Er}

and

{}^{151}{Tb}

{}^{150 - 153}{Dy}

were produced by bombarding

{}^{147}{Sm}

and

{}^{144}{Nd}

, respectively, with

{}^{12}C

ions accelerated in the Oak Ridge isochronous cyclotron. With the use of a gas-jet-capillary transport system

α

-particle, x-ray, and

γ

-ray spectra were measured simultaneously and

α

-decay branching ratios deduced for the above mentioned nuclides. The ratios were determined primarily by measuring the number of

K α_{1}

x rays emitted and then applying appropriate correction factors to obtain the total number of electron capture and positron decays. In addition, for

{}^{150, 152, 153}{Dy}

it was possible to deduce alternate, and thus independent,

α

-decay branching ratios from

γ

-ray spectral measurements. Within error limits the two sets of values were found to be in agreement. Because of the essentially equal half-lives of

{}^{151}{Tb}

and

{}^{152}{Tb}

the α branch for

{}^{151}{Tb}

could not be determined from the

K α_{1}

ray intensity; instead it was deduced solely on the basis of its known decay to levels in

{}^{151}{Gd}

. Branches for

{}^{149}{Tb}

{}^{149}{Tb}^{m}

, and

{}^{150}{Tb}

, as well as for the fine structure

α

decays observed in the case of

{}^{153}{Dy}

and

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α-decay branching ratios forTb151,Dy150−153, andEr152−155